Authority: Flemish Land Agency. Gulden-Vlieslaan 72, 1060 Brussels

Transcription

1 Authority: Flemish Lnd Agency Gulden-Vliesln 72, 16 Brussels Follow-up of monitoring network of frms under Directive 28/64/EG in order to ssess the impct of derogtion on the wter qulity Finl report Februry 215 Consortium: Soil Service of Belgium, nd Ktholieke Universiteit Leuven, Deprtment of Erth nd Environmentl Sciences Soil Service of Belgium W. de Croyln 48, 31 Leuven-Heverlee KU Leuven Consortium Deprtment of Erth nd Environmentl Sciences Celestijnenln 2E, 31 Leuven

2 Consortium members: Soil Service of Belgium Wendy Odeurs, Sofie Mes, Dvy Vndervelpen, Mi Tits, Annemie Elsen, Jn Bries nd Hilde Vndendriessche KU Leuven Jn Diels nd Jos Vn Orshoven Cittion: Odeurs, W., Mes, S., Vndervelpen, D., Tits, M., Elsen, A., Diels, J., Vn Orshoven, J., Bries, J. nd Vndendriessche, H., (215). Follow-up of monitoring network of frms under Directive 28/64/EG in order to ssess the impct of derogtion on the wter qulity. Finl report Februry 215 Study crried out under the uthority of the Flemish Lnd Agency by the Soil Service of Belgium nd the Deprtment of Erth nd Environmentl Sciences (KU Leuven). 336 pp. Steering Group members: Koen Desimpelere (VLM), Sofie Ducheyne (VLM), Luc Gllopyn (VLM), Kristof Buwens (VLM), Els Goethls (VLM), Pul Vn Der Sluys (VLM), Ri Gielis (VLM), Dirk Vn Gijseghem (LV-AMS), Rlf Eppinger (VMM), Kor Vn Hoof (VMM), Tom D Heygere (VMM), Andy Oeyen (LV-AMS), Guy Depretere (ABS), Albert Bohnen (BB), Guy Vndepoel (BB), Philip Colson (VAC), ALUMENCO, An Jmrt (BioForum), Annelore Nys (Ntuurpunt), Jeroen Gillbel (GGLV), Kroline D Hene (Onderzoekspltform Duurzme Bemesting), Georges Hofmn (Onderzoekspltform Duurzme Bemesting), John Vn Wes (Onderzoekspltform Duurzme Bemesting), Joost Slomez (LNE), Sibylle Verpletse (Kbinet Minister vn Leefmilieu), Annelise Bkelnts (VMM).

3 Summry The Europen Commission decided on June 29 th 211 to continue the possibility, with regrd to the region of Flnders, to pply higher mount of livestock mnure in comprison with the generl limittion of 17 kg N from livestock mnure per hectre (derogtion request). The selection of crops on which derogtion could be requested remined nd the selection of livestock mnure which could be pplied on derogtion prcels lso remined the sme. This derogtion decision held lso conditions imposed on the competent uthorities with regrd to monitoring, controls nd reporting. The objective of this investigtion is the follow-up of monitoring network of t lest 15 frms in order to ssess the impct of derogtion on the nitrogen nd phosphorus losses from the soil nd on the wter qulity. In this reserch the first monitoring network is evluted, re-estblished nd followed-up. The originl set-up of the monitoring network of 188 frms nd 227 prcels ws evluted. The im ws to retin s mny frms nd prcels of the former monitoring network s possible. This wy, the dt collected in the first reserch period (29-211) could be used s well. After screening, the monitoring network consists of 175 different frms in 211. For 85 prcels (out of 217 selected prcels) derogtion ws requested in 211. In 212, 213 nd 214 the monitoring network consisted of 216 prcels. Derogtion ws pplied on 94, 111 nd 8 prcels. Similr to 211, grss ws most frequently cultivted on derogtion prcels followed by mize. In order to compre derogtion with no derogtion prcels nd to investigte the effect of derogtion on the wter qulity, both soil nd wter smples re tken. Nitrte smples re tken from to 9 cm in three lyers (-3, 3-6 nd 6-9 cm) before nd fter winter. The mount of nitrte is determined in ech soil lyer. On selection of prcels second soil smple is tken before nd fter winter, the deep soil smple. A soil smple from 9 to 12 cm on which the mount of nitrte nd phosphorus (in mmonium-lctte extrct) is mesured. In ddition, on the deep soil smples the totl mount of phosphorus nd the different frctions (DIP nd DOP) of phosphorus re determined. A stndrd soil smple is tken between Jnury nd Mrch 212 for stndrd soil nlysis. Besides soil texture, ph nd crbon, vriety of nutrients (phosphorus, mgnesium, potssium, clcium nd sodium) re determined. Wter smples re tken from MAP smpling points groundwter, monitoring wells, cnls, ditches nd drins. Ech wter smple is linked to one specific prcel in the monitoring network. In these smples the mount of nitrte nd phosphorus (PO 4 -P) is mesured. In 5 % of the 1

4 wter smples the totl mount of phosphorus nd the different frctions (DIP nd DOP) of the phosphorus re mesured. In the beginning of 212 stndrd soil smple ws tken on ech prcel of the monitoring network. The results of the stndrd soil nlysis showed tht the long term ppliction of derogtion or no derogtion hs no consequence for the phosphorus content of the soil. Since the composition of orgnic fertilisers cn be highly vrible, livestock mnure used on prcels in the monitoring network, ws smpled. The nlyses re used to clculte the correct input of nutrients (N nd P 2 O 5 ) on individul prcel level, necessry to clculte the nutrient blnces. On derogtion prcels, grss nd mize, consequently more orgnic nitrogen fertilistion is pplied. However minerl nitrogen fertilistion on derogtion prcels is not more restricted thn on no derogtion prcels. So not only orgnic fertilistion but lso totl nitrogen fertilistion is higher on derogtion prcels. Discrepncy between derogtion nd no derogtion prcels is most pronounced on grss prcels. This conclusion is very importnt since it mkes the comprison of derogtion (supposed nd legitimte higher supply of orgnic N) legitimte. The comprison of the nitrte residue on derogtion nd no derogtion prcels is strt to investigte the effect of derogtion on the qulity of surfce nd groundwter, since the nitrte residue is the mount of nitrte-n which is susceptible to leching during the winter. No sttisticl differences were detected between derogtion nd no derogtion prcels in nitrte residue in the monitoring period This ws confirmtion of the lck of sttisticl significnt difference in nitrte residue of derogtion nd no derogtion prcels in utumn 29 nd 21. Also in the deep soil lyer 9-12 cm in generl no sttisticl significnt differences were found between derogtion nd no derogtion prcels. Wter smples relted to the prcels of the monitoring network re essentil. Wter smples were tken twice yer, before nd fter winter. For surfce wter, smples re tken t drins nd in cnls nd ditches. The wter smples of drins, cnls nd ditches re used s n indiction of the nitrte concentrtion in the surfce wter. The verge vlues were lmost lwys below the threshold vlue of 5 mg NO 3 /l. However t ech smpling moment lso high nitrte concentrtions were mesured. More importnt nd trustworthy re the mesurements t the MAP smpling points groundwter nd the self plced monitoring wells. In function of the trvel time nd the infiltrtion re the smpling point cn be linked directly to n individul prcel. Comprison of the wter qulity in function of the ppliction of derogtion or no derogtion is possible when the prcel chrcteristics re linked to the corresponding wter nlyses in 2

5 function of the trvel time. This comprison ws complete for the prcel chrcteristics of 29 nd 21. Nor for prcel chrcteristics of 29 nor for those of 21 the nitrte concentrtion in the groundwter ws higher fter the ppliction of derogtion. The highest verge concentrtions of orthophosphte-p were mostly mesured in wter smples originting from drins, cnls nd ditches. As for nitrte those wter smples re used s n indiction. The decresing trend in phosphte concentrtion in the shllow groundwter noticed in the former monitoring network ws continued t the MAP smpling points until spring 213. At the monitoring wells this trend continued until utumn 213, with exception of sudden higher verge vlue in utumn 212. In order to investigte the leching of nitrte during winter, soil smple is tken in utumn nd spring. The Burns model is used to predict the movement of unbsorbed nions like nitrte. Clcultions with the Burns model were done for the winters , nd The Burns model results in prediction of the mount of nitrte in the soil profile fter winter. Those predicted vlues correlte significntly with the mesured mounts of nitrte fter winter. The estimted mount of leched nitrte did not differ between derogtion nd no derogtion prcels, not for prcels cultivted with grss nor for prcels cultivted with mize. This grees with the fct tht there s no difference in the mount of nitrte in the soil profile before nd fter winter between derogtion nd no derogtion prcels. In order to explin the lck of differences in soil nd wter, in the nitrte residue nd the nitrte concentrtion in groundwter, despite the higher input of totl N on the derogtion prcels, nutrient blnces re clculted for the individul prcels. Two different pproches re used to clculte nutrient blnce: the input/output blnce nd nitrogen-soil blnce. Nor in 212, 213 or 214 sttisticl significnt differences were found between the Input-output blnce results of derogtion nd no derogtion prcels. Nor in 212, 213 or 214 sttisticl significnt differences were found between the nitrte-n soil blnce results of derogtion nd no derogtion prcels. Representing the nitrte-n soil blnce in reltive terms in function of the totl input, shows clerly the impct of the minerlistion (f.i. in verge 53 % of the totl N- input on mize prcels in 214) on the nitrte-n soil blnce nd the impct of the cover crop on derogtion prcels. Yield smpling confirmed even on limited number of prcels, the high vribility in N-export, f.i. more thn 1 kg N on mize prcels, 227 kg N/h versus 14 kg N/h. 3

6 The process fctor ws evluted for the prcels of the network, when monitoring well or MAP smpling point ws present. It is confirmed gin tht the process fctor groundwter is highly vrible without cler sptil pttern. Bsed on this extensive network of prcels nd the vriety of mesurements on prcels nd in the wter, derogtion in Flnders hs no negtive impct on the wter qulity. 4

7 Smenvtting De Europese Commissie besloot op 29 juni 211 toe te lten dt Vlmse lndbouwers ook gedurende de periode onder strikte voorwrden fwijken vn de lgemene bemestingsnorm vn 17 kg stikstof per hectre per jr uit dierlijke mest (derogtie). De teelten wrop derogtie kn worden toegepst en de dierlijke mest die binnen de derogtie mg worden toegepst, bleven ongewijzigd. Ook deze derogtiebeschikking omvtte voorwrden nr de overheid toe. Voorwrden omtrent monitoring, controle en rpportering. Het doel vn dit onderzoek ws het opvolgen vn een monitoringnetwerk vn minstens 15 bedrijven om de impct vn derogtie op de stikstof- en fosforverliezen uit de bodem en de wterkwliteit te beplen. In dit onderzoek werd het eerder opgezette monitoringnetwerk in eerste instntie geëvlueerd en ndien verder opgevolgd. De originele opzet vn het monitoringnetwerk vn 188 bedrijven en 227 percelen werd geëvlueerd. Het doel ws om zo veel mogelijk bedrijven en percelen uit het eerder opgezette monitoringnetwerk te behouden. Op deze mnier kunnen de dt bekomen in de eerste onderzoeksperiode (29-211) verder ngevuld en gebruikt worden. N screening in de eerste fse bestond het netwerk uit 175 bedrijven in 211. In 211 werd op 85 vn de 217 geselecteerde percelen derogtie ngevrgd. In 212, 213 en 214 werden 216 percelen opgevolgd. Net zols in 211 wren grs en mïs de meest voorkomende teelten. In 212, 213 en 214 werd derogtie toegepst op 94, 111 en 8 percelen. Om derogtie- en niet-derogtiepercelen te vergelijken en om het effect vn derogtie op de wterkwliteit te chterhlen, werden zowel bodem- ls wterstlen genomen. Bodemstlen om de hoeveelheid nitrt te beplen, werden voor en n de winter genomen tot 9 cm diepte, per bodemlg vn 3 cm (-3, 3-6 nd 6-9 cm). De hoeveelheid nitrt wordt bepld per bodemlg. Op een selectie vn percelen wordt een tweede stl genomen voor en n de winter. Een diep bodemstl in de lg vn 9 tot 12 cm, wrop de hoeveelheid nitrtstikstof en het fosforgehlte (in mmoniumlctt extrct) bepld wordt. Op de diepe bodemstlen wordt bijkomend de totle hoeveelheid fosfor en de verschillende fosforfrcties (orgnische en minerle in oplossing) bepld. Een stndrdgrondstl werd genomen tussen jnuri en mrt 212. Nst de bodemtextuur, de zuurtegrd en het orgnische koolstofgehlte wordt ook het P-, Mg-, K-, C- en N-gehlte bepld. Wterstlen worden genomen n MAP-meetpunten grondwter, n zelfgepltse peilbuizen, n dringes en in grchten en beken. Elk wterstl wordt gekoppeld n één specifiek perceel 5

8 vn het derogtiemonitoringnetwerk. Op de wterstlen wordt het nitrt- en orthofosftgehlte bepld. Op de helft vn de wterstlen wordt het totle fosforgehlte bepld lsook de verschillende fosforfrcties. Begin 212 werd op elk perceel vn het derogtiemonitoringnetwerk een stndrdstl genomen. De resultten vn de stndrdgrondontleding toonden dt lngdurige derogtie geen effect heeft op het fosforgehlte vn de bodem. Angezien de smenstelling vn orgnische mest sterk kn verschillen, werd lle dierlijke mest die op de percelen vn het derogtiemonitoringnetwerk werd ngewend, bemonsterd. Deze nlyseresultten werden gebruikt om de nutriënteninput (N en P 2 O 5 ) per perceel correct te begroten, wt nodig is om de nutriëntenblnsen te kunnen berekenen. Op de derogtiepercelen, zowel grs ls mïs, wordt consequent meer orgnische stikstof ngewend. Desondnks wordt op de derogtiepercelen niet minder minerle stikstof toegepst. Bijgevolg wordt op de derogtiepercelen niet enkel meer orgnische stikstof mr ook meer totle stikstof ngewend. Dit onderscheid tussen derogtie en niet-derogtiepercelen is het meest uitgesproken op grslnd. Dit besluit, dt op de derogtiepercelen wel degelijk meer orgnische (en totle) mest wordt toegepst, is zeer belngrijk. Het rechtvrdigt immers de vergelijking vn derogtie- en nietderogtieprktijken. De vergelijking vn het nitrtresidu op derogtie- en niet-derogtiepercelen is bijgevolg een eerste stp in het beplen vn het effect vn derogtie op de kwliteit vn het grond- en oppervlktewter, ngezien het nitrtresidu de hoeveelheid nitrtstikstof is die gevoelig is n uitspoeling tijdens de winter. Tijdens de monitoring in de periode konden geen sttistische verschillen worden ngetoond tussen het nitrtresidu op derogtie en nietderogtiepercelen, net ls in njr 29 en njr 21. Ook in de diepe bodemlg 9-12 cm werd doorgns geen sttistisch significnt verschil gevonden tussen derogtie- en nietderogtiepercelen. Wterstlen die kunnen gekoppeld worden n de percelen vn het derogtiemonitoringnetwerk zijn essentieel. De meetpltsen voor wter werden twee keer per jr bemonsterd, voor en n de winter. Voor oppervlktewter werden wterstlen genomen n dringes en in beken en grchten. De wterstlen vn dringes, beken en grchten geven eerder een indictie vn de nitrtconcentrtie in het oppervlktewter. De gemiddelde nitrtconcentrtie lg ngenoeg steeds onder de drempelwrde vn 5 mg NO 3 /l. Toch werden op elk moment vn stlnme ook hoge nitrtconcentrties gemeten. Vn groter belng en meer betrouwbr zijn de metingen 6

9 en wterstlen n MAP meetpunten vn het MAP meetnet grondwter in Vlnderen en n de zelfgepltste peilbuizen. Rekening houdende met de reistijd en het intrekgebied kunnen deze meetpunten één op één gekoppeld worden n een perceel vn het derogtiemonitoringnetwerk. Vergelijking vn de wterkwliteit in functie vn het l dn niet toepssen vn derogtie is mogelijk wnneer de perceelskrkteristieken gekoppeld worden n de corresponderende wternlyses door rekening te houden met de reistijd. Dergelijke vergelijkingen zijn volledig voor de perceelsinvloeden vn 29 en 21. Noch het toepssen vn derogtie in 29, noch het toepssen vn derogtie in 21 leidde tot hogere nitrtconcentrties in het grondwter. Derogtie heeft bijgevolg geen negtieve impct op het nitrtgehlte in het grondwter. De hoogste orthofosftwrden werden doorgns gemeten in wterstlen vn dringes, beken en grchten. Deze wterstlen werden net zols voor de nitrtconcentrties ook voor de fosftconcentrties ngewend ls indictor, niet voor het vstleggen vn sttistische verschillen tussen derogtie en niet-derogtiepercelen. De dlende trend in fosftconcentrtie in het oppervlkkige grondwter die in de vorige monitoringperiode werd opgemerkt, werd verdergezet in de MAP meetpunten grondwter tot voorjr 213. In de peilbuizen werd deze evolutie verder wrgenomen tot njr 213, met uitzondering vn een plotse hoge gemiddelde wrde in njr 212. Om de uitspoeling tijdens de winter in te schtten worden bodemstlen genomen in het njr en in het voorjr. Het model vn Burns wordt gebruikt om de beweging vn vrije nionen, zols NO3 -, te voorspellen. De berekeningen met het model vn Burns werden uitgevoerd voor de winters , nd Het resultt vn het model vn Burns is een voorspelde nitrtreserve in het voorjr. Deze voorspelde wrden correleerden significnt met de gemeten nitrtvoorrden n de winter. De begrootte nitrtuitspoeling verschilde niet tussen derogtie en niet-derogtiepercelen, noch voor grspercelen, noch voor mïspercelen. Dit strookt met de vststellingen dt noch de nitrtresidu s noch de voorjrsreserves op derogtie- en nietderogtiepercelen verschillen. Om het uitblijven vn verschillen in bodem en wter, in nitrtresidu en nitrtgehlte in het grondwter te kunnen verklren ondnks de ngetoonde hogere N-input op derogtiepercelen, worden op perceelsniveu nutriëntenblnsen opgesteld. De nutriëntenblns werd op twee verschillende mnieren benderd: de input/output blns en de N-bodemblns. Noch in 212, 213 of 214 werd een sttistisch significnt verschil vstgesteld tussen het inputoutputblnsresultt vn derogtie- en niet-derogtiepercelen. Noch in 212, 213 of 214 werd een sttistisch significnt verschil vstgesteld tussen het N-bodemblnsresultt vn derogtie- 7

10 en niet-derogtiepercelen. Wnneer de N-bodemblns reltief werd voorgesteld, nmelijk door lle prmeters vn de blns f te wegen ten opzichte vn de totle input, bleek duidelijk de impct vn de minerlistie (bv tot gemiddeld 53 % vn de totle input op de mïspercelen in 214) op de N-bodemblns. Mr ook het grotere belng vn vnggewssen op derogtiepercelen dn op niet-derogtiepercelen bleek duidelijk. Proefoogsten toonden zelfs op een beperkt ntl percelen grote verschillen in N-export, bijvoorbeeld meer dn 1 kg N/h op mïspercelen, 227 kg N/h versus 14 kg N/h. De procesfctor grondwter werd geëvlueerd voor percelen, met gekoppeld MAP-meetpunt of peilbuis, uit het derogtiemonitoringnetwerk. Deze evlutie bevestigde dt de procesfctor grondwter sterk vrieert over Vlnderen en dt er bijkomend geen duidelijk ptroon in die spreiding kn gevonden worden. Op bsis vn dit uitgebreide netwerk vn percelen en de diversheid vn beplingen op perceelsniveu en op het niveu vn het wter, kn gesteld worden dt derogtie onder Vlmse omstndigheden geen negtieve impct heeft op de wterkwliteit. 8

11 Tble of Contents Summry... 1 Smenvtting Introduction Evlution of 175 frms/217 prcels Frms Prcels Prcel chrcteristics bsed on the stndrd soil nlysis The different soil fertility clsses Fertilistion nd liming dvice Stndrd soil smple for grsslnd in spring Stndrd soil smple for rble lnd in spring Prcel chrcteristics bsed on the N-INDEX N-INDEX for grsslnd in spring N-INDEX for rble lnd in spring N-INDEX for grsslnd in spring N-INDEX for rble lnd in spring N-INDEX for grsslnd in spring N-INDEX for rble lnd in spring Fertilistion Livestock mnure Amount of supplied nutrients

12 5.3 Fertilistion prctices Comprison Fertilistion prctices Conclusion Nitrte in the soil profile Nitrte in utumn All crops on ll soil textures Derogtion crops on ll soil textures Derogtion crops on sndy soils Grss nd mize on sndy soils Derogtion crops on sndy lom soils Grss nd mize on sndy lom soils Nitrte in utumn 211, prcels which were continuously under derogtion/no derogtion during All crops on ll soil textures Derogtion crops on ll soil textures Derogtion crops on sndy soils Grss nd mize on sndy soils Sndy lom soils Grss nd mize on sndy lom soils Nitrte in utumn 211 in the deeper soil lyer Nitrte in spring All crops on ll soil textures Derogtion crops on ll soil textures

13 6.4.3 Derogtion crops on sndy soils Grss nd mize on sndy soils Derogtion crops on sndy lom soils Grss nd mize on sndy lom soils Nitrte in spring 212, prcels which were continuously under derogtion/no derogtion during All crops on ll soil textures Derogtion crops on ll soil textures Derogtion crops on sndy soils Grss nd mize on sndy soils Derogtion crops on sndy lom soils Grss nd mize on sndy lom soils Nitrte in spring 212 in the deeper soil lyer Nitrte in utumn All crops on ll soil textures Derogtion crops on ll soil textures Derogtion crops on sndy soils Grss nd mize on sndy soils Derogtion crops on sndy lom soils Grss nd mize on sndy lom soils Nitrte in utumn 212, prcels which were continuously under derogtion/no derogtion during All crops on ll soil textures Derogtion crops on ll soil textures Derogtion crops on sndy soils Grss nd mize on sndy soils

14 6.8.4 Derogtion crops on sndy lom soils Grss nd mize on sndy lom soils Nitrte in utumn 212 in the deeper soil lyer Nitrte in spring All crops on ll soil textures Derogtion crops on ll soil textures Derogtion crops on sndy soils Grss nd mize on sndy soils Derogtion crops on sndy lom soils Grss nd mize on sndy lom soils Nitrte in spring 213 in the deeper soil lyer Nitrte in utumn All crops on ll soil textures Derogtion crops on ll soil textures Derogtion crops on sndy soils Grss nd mize on sndy soils Derogtion crops on sndy lom soils Grss nd mize on sndy lom soils Nitrte in utumn 213, prcels which were continuously under derogtion/no derogtion during Nitrte in utumn 213 in the deeper soil lyer Nitrte in spring All crops on ll soil textures Derogtion crops on ll soil textures Derogtion crops on sndy soils Grss nd mize on sndy soils

15 Derogtion crops on sndy lom soils Grss nd mize on sndy lom soils Nitrte in spring 214, prcels which were continuously under derogtion/no derogtion during Nitrte in spring 214 in the deeper soil lyer Nitrte in utumn All Crops on ll soil textures Derogtion crops on ll soil textures Derogtion crops on sndy soils Grss nd mize on sndy soils Derogtion crops on sndy lom soils Grss nd mize on sndy lom soils Nitrte in utumn 214, prcels which were continuously under derogtion/no derogtion during Nitrte in utumn 214 in the deeper soil lyer Nitrte in the deeper soil lyer Conclusion Nitrte in the surfce nd groundwter Cnls, ditches nd drins Shllow groundwter (MAP smpling points groundwter nd monitoring wells) Prcel chrcteristics of Prcel chrcteristics of Prcel chrcteristics of Prcel chrcteristics of Prcel chrcteristics of Nitrte in the soil wter

16 7.4 Cse studies Conclusion Phosphorus in the soil profile P-AL in the stndrd soil smple P-AL in the stndrd soil smple, prcels which were continuously under derogtion/no derogtion during P-AL in the deep soil smples (9-12 cm) Phosphte sturtion degree Conclusion Phosphorus in the surfce nd groundwter Drins, cnls, ditches nd smpling points DIP, DOP nd totl P Conclusion Orgnic crbon in the soil profile Orgnic crbon in the stndrd soil smple, prcels which were continuously under derogtion/no derogtion during Conclusion Burns model Input prmeters Winter Winter Winter Conclusion Nutrient blnce Input/output blnce Input of orgnic nd minerl fertilisers

17 Input of tmospheric deposition Output of emission losses Output of the hrvested crop Blnce result Blnce result Blnce result Nitrte-N soil blnce Nitrte in the soil profile before the growing seson Fertilistion (orgnic nd minerl) Minerlistion Uptke by the cultivted crop Leching nd tmospheric deposition Nitrte residue Nitrte-N soil blnce results Nitrte-N soil blnce results Nitrte-N soil blnce results Yield smpling Grsslnd Mize prcels Grsslnd Mize prcels Nitrte-N/soil blnce of 21 nd nitrte in monitoring wells, bsed on the trvel time Conclusion Simultion of the effect of derogtion on the level of Flnders ArcNEMO in generl

18 13.2 Generl procedure of BAM The no derogtion scenrio (scenrio 2) Results scenrio Conclusion Process fctors for groundwter Clcultion of the process fctor for groundwter Determintion of the rechrge zone of monitoring wells nd of trvel times from soil to well Clcultion of the verge nitrte concentrtion t the bottom of the root zone (-9 cm) Clcultion of the process fctors Results nd discussion Reltionship between mesured residul nitrte content nd soil solution nitrte concentrtion t -9cm Vrition of the process fctor for groundwter Conclusion Annex Annex Annex Climte Climte Climte Climte

19 ABBREVIATIONS AL CF DIP DOP EEC IC ICP KU Leuven MAP PF PSC PSD SSB VLM VMM Ammonium-lctte Continuous Flow Dissolved Inorgnic Phosphorus Dissolved Orgnic Phosphorus Europen Economic Community Ion Chromtogrphy Inductive Coupled Plsm Ktholieke Universiteit Leuven Mnure Action Progrm Process Fctor Phosphte Sorption Cpcity Phosphte Sturtion Degree Soil Service of Belgium Flemish Lnd Agency Flemish Environment Agency 17

20 1 Introduction The objective of this reserch is the follow-up of monitoring network of t lest 15 frms (trget of 18 frms nd 225 prcels) in order to ssess the impct of derogtion on the nitrogen nd phosphorus losses from the soil nd on the wter qulity. If derogtion would hve significnt impct on the wter qulity, it is of gret importnce to identify the underlying cuses nd to determine the precise impct on the wter qulity. The monitoring network provides dt on fertilistion nd frming prctices on the prcels, nitrogen nd phosphorus concentrtion in soil wter, nitrogen in the soil profile, nitrogen nd phosphorus losses through the root zone into the groundwter, nitrogen nd phosphorus losses by surfce nd subsurfce run-off. In this wy, the impct on the wter qulity cn be evluted for prcels under derogtion nd no derogtion conditions. The monitoring network should be representtive for the different soil textures, crops nd fertilistion prctices commonly present in Flnders. The existing MAP monitoring network for groundwter (MAP smpling points groundwter) ws chosen s bsis for the set-up of the monitoring network. The MAP monitoring network is dense network of 2,17 mesuring points distributed over Flnders. These MAP monitoring sites hve smll infiltrtion res, so the wter qulity of one MAP monitoring site cn be linked to n individul prcel. In Vndervelpen et l., 211, the infiltrtion re nd the trvel time of the wter from the root zone to the MAP smpling point groundwter ws clculted for every MAP smpling point groundwter. However, the selection from the MAP smpling points groundwter did not result in network of 225 prcels (s requested). Therefore, in the former monitoring project (Vndervelpen et l., 211) prcels were selected from cndidte frmers. In order to mesure the wter qulity on these prcels monitoring wells were plced. On prcels with long trvel time (>3 yers), no monitoring well ws plced. In these prcels the wter qulity is mesured by smpling cnls, ditches or drins. More thn hlf of the prcels in the network consist of sndy soils. Hlf of the prcels re cultivted with grss nd pproximtely 3 % re cultivted with mize. This wy the monitoring network is representtive for the griculturl prctices on derogtion prcels in Flnders since derogtion is mostly requested by diry cow frms on sndy soils cultivted with grss or mize. 18

21 The first prt of this report dels with the follow-up nd evlution of the existing monitoring network (Vndervelpen et l., 211). For 211, 217 prcels nd 175 frms were retined in the monitoring network. Tble 1 shows the 217 prcels in the network for the different combintions of soil texture nd cultivted crop. For 212, 213 nd 214, 216 prcels were retined in the monitoring network. Tble 2 illustrtes the time scle of the different mesurements on the prcels. More detils on the selection procedure nd the different smples tken t prcel level re discussed in the report of the former monitoring project (Vndervelpen et l., 211). The second prt of this report will discuss the results of the field mesurements. For ech mesured prmeter it will be investigted whether there is globl difference between derogtion nd no derogtion prcels in generl (ll crops, ll soil textures). Next, more specific combintions of soil texture nd cultivted crop will be nlysed sttisticlly. Nitrte nd phosphorus re the two most importnt prmeters in order to mesure the effect of derogtion on wter qulity, s such they will be discussed extensively in this report. In order to compre derogtion with no derogtion prcels nd to investigte the effect of derogtion on the wter qulity, both soil nd wter smples re tken. First, nitrte smple is tken from to 9 cm in three lyers (-3, 3-6 nd 6-9 cm) before nd fter winter. The mount of nitrte is determined in ech soil lyer. A second soil smple (the deep soil smple) is tken on selection of prcels. On these prcels soil smple is tken from 9 to 12 cm. Here the mount of nitrte nd phosphorus (in mmonium-lctte extrct) is mesured. In ddition, in 5 % of the deep soil smples the totl mount of phosphorus nd the different frctions (DIP nd DOP) of phosphorus re determined. A third soil smple (stndrd soil smple) is tken between Jnury nd Mrch for stndrd soil nlysis. Besides soil texture, ph nd crbon, vriety of nutrients (phosphorus, mgnesium, potssium, clcium nd sodium) re determined. Besides the soil smples, wter smples re tken from MAP smpling points groundwter, monitoring wells, cnls, ditches nd drins. Ech wter smple is linked to one specific prcel in the monitoring network. In these smples the mount of nitrte nd phosphorus (PO 4 -P) is mesured. In 5 % of the wter smples the totl mount of phosphorus nd the different frctions (DIP nd DOP) of the phosphorus re mesured. In order to investigte the difference between derogtion nd no derogtion prcels for different combintions of soil texture nd cultivted crop, n ANOVA model ws used with.5 significncy level (p-vlue). Since normlity of the dt nd homogeneity of the vrinces re required, logrithmic trnsformtion of the dt is crried out to fulfil these conditions. 19

22 Tble 1: Overview of ll the prcels in the monitoring network, Flnders, 211, 212, 213 nd 214. Derogtion No derogtion Grss Mize Beets Winter whet Grss Mize Beets Winter whet Other Totl Snd Sndy lom Lom Cly Totl Snd Sndy lom Lom Cly Totl Snd Sndy lom Lom Cly Totl Snd Sndy lom Lom Cly Totl

23 Tble 2: Time scle of mesurements. Time scle Yer Month Soil smples Stndrd soil smple Nitrte smple Deep soil smple Wter smples MAP smple point Monitoring wells Drins Cnls nd ditches Wter from deep soil smple Mnure smples Yield smples grsslnd Yield smples mize 21

24 2 Evlution of 175 frms/217 prcels The originl set-up of monitoring network of 188 frms nd 227 prcels ws evluted. A detiled description of the set-up of the monitoring network cn be consulted in the first intermedite report of 2 th of Jnury 29: Estblishment nd follow-up of monitoring network of frms to ssess the impct of derogtion on the wter qulity, First intermedite report 2 Jnury 29 (Vndervelpen et l., 29). The im is to retin s mny frms nd prcels of the existing monitoring network s possible. This wy, the dt collected in the first reserch period (29-211) cn be used s well. At first, the frmers were contcted to verify their willingness to continue to prticipte in the monitoring network for the period A number of frmers were eliminted from the network since they were no longer the owner of the prcel. The new owners of those prcels were contcted but some of them were not interested to prticipte in the network. In the existing monitoring network, frms nd prcels were selected strting from MAP smpling points groundwter, the prticiption of cndidte frms nd the selection of dditionl prcels grsslnd. In the next tbles nd figures the fetures of the retined frms nd prcels re discussed. The most importnt fetures re derogtion, soil texture nd cultivted crop. The geogrphicl loction of the prcels is lso shown (Figure 1). Although homogeneous geogrphicl distribution ws not required, the selected prcels of the monitoring network re well spred over the region of Flnders. 2.1 Frms After screening, the monitoring network consists of 175 different frms in 211. These 175 frms re lmost eqully divided in frms with derogtion nd frms without derogtion in 211 (Tble 3). In 212, one prcel, nd s consequence one frmer, ws excluded from the monitoring network since no fertilistion nor ny lnd mngement prctices were executed on this prcel. In 213 the monitoring network consists of 173 different frms. Frms tht cultivted more thn one prcel of the monitoring network stopped cultivting some prcels fter winter Becuse other frms cultivte these prcels in 214, the network comprised 175 frms in

25 Tble 3: Number of frms prticipting in the monitoring network, clssified in derogtion nd no derogtion frms in 211, 212, 213 nd 214. Derogtion No derogtion Totl Prcels The monitoring network consists of 217 prcels in 211. Figure 1 shows the geogrphicl loction of the 217 prcels in the monitoring network. Distinction hs been mde between derogtion (green) nd no derogtion (red) prcels for 211. The prcels re locted ll over the region of Flnders, but most prcels re locted in the Kempen, the Flemish snd region nd Sndy lom region. Since derogtion occurs mostly in these regions it is importnt to hve the highest number of prcels there. Since derogtion s well s no derogtion prcels re locted in ll regions, comprison will be possible on different soil textures. Tble 4 nd Tble 5 show the different combintions of soil textures nd crops seprtely for the derogtion nd no derogtion prcels. For 85 prcels (out of 217 selected prcels) derogtion ws requested in 211. More thn hlf of the prcels re cultivted on sndy soil, followed by sndy lom. It needs to be noted tht ll soil textures used in this report re ccording to the Belgin clssifiction. Grss is most frequently cultivted on derogtion prcels followed by mize. Derogtion prcels need to be cultivted with derogtion crop (grss, mize, beets, winter whet), therefore the column other is empty. Since 212 the monitoring network consists of 216 prcels. Grss nd mize were ech yer the most importnt crops. 23

26 Figure 1: Loction of the 217 prcels in the monitoring network on the griculturl regions of Flnders in 211. The prcel mrked with blck circle ws discrded from the network since

27 Tble 4: Number of derogtion prcels for the different combintions of soil textures nd crops in 211, 212, 213 nd 214. Grsslnd Mize Beets Winter whet Other Totl 211 Snd Sndy lom Lom Cly Totl Snd Sndy lom Lom Cly Totl Snd Sndy lom Lom 1 1 Cly Totl Snd Sndy lom Lom Cly Totl In Tble 5 the different combintions for the no derogtion prcels re listed. The monitoring network comprised 132 no derogtion prcels in 211. On no derogtion prcels lso other crops thn only derogtion crops (vegetbles,...) re cultivted. Due to crop rottion it is possible tht the next yer derogtion crop will be cultivted on these prcels. Tble 5 shows tht the combintions of snd nd sndy lom soils with grsslnd nd mize re the most importnt. This ws lso the cse for the derogtion prcels (Tble 4). Comprison between derogtion nd no derogtion prcels cn be mde especilly for these combintions. 25

28 Tble 5: Number of no derogtion prcels for the different combintions of soil textures nd crops in 211, 212, 213 nd 214. Grsslnd Mize Beets Winter whet Other Totl 211 Snd Sndy lom Lom Cly Totl Snd Sndy lom Lom Cly Totl Snd Sndy lom Lom Cly Totl Snd Sndy lom Lom Cly Totl Prcel chrcteristics bsed on the stndrd soil nlysis On ech prcel of the monitoring network, stndrd soil smple ws tken only once, in the beginning of 212. The nlysis of stndrd soil smple gives n insight into the soil fertility of the different prcels. The most importnt prmeters of the stndrd soil smple re soil texture, ph-kcl, percentge orgnic crbon (%C) nd mount of nutrients (P, K, Mg, N nd C). An optiml ph is necessry for the vilbility of nutrients in the soil nd is thus importnt for crop growth. The percentge of orgnic crbon cn be linked to the mount of orgnic mtter in the soil (orgnic mtter = percentge orgnic crbon multiplied with 1.72). This prmeter is importnt in order to estimte minerlistion. A stndrd soil smple in grsslnd is tken from to 6 cm, since in this lyer the root density is mximl. In rble lnd the stndrd soil smple is tken from to 23 cm. Optiml conditions for crop growth re necessry in these soil lyers. 26

29 A stndrd soil smple is obtined from homogenous prcel with mximum surfce of 2 hectres. A representtive smple consists of different subsmples tken t vrious loctions in the prcel. For grsslnd one smple consists of 35 subsmples, for rble lnd 25 subsmples re sufficient. After smpling, the stndrd soil smple is trnsported to the nlyticl lbortory. Here it is dried for 24 hours t temperture of 7 C. Next the smple is pulverized (only necessry for soils with certin percentge of cly) nd sieved (2 mm). The ph is mesured in KCl solution nd orgnic crbon (%C) is determined with the dpted Wlkley nd Blck method. For the different nutrients (P, K, Mg, C nd N) n extrction with mmonium lctte is used. K, Mg, C, N nd P re mesured with ICP. Finlly, the soil texture is determined mnully by plption. 3.1 The different soil fertility clsses Bsed on the stndrd soil nlysis, the frmer receives fertilistion nd liming dvice. This dvice is bsed on field tril reserch combined with experience in the griculturl nd the horticulturl sector (Boon et l., 29; Mes et l., 212). For ech prmeter (%C, P, ph...), seven soil fertility clsses re estblished (rnging from very low (strongly cid for ph) to very high (pety for %C)) depending on soil texture nd orgnic crbon content of the soil. These soil fertility clsses re distinct for grsslnd nd rble lnd. The middle clss is the optiml level. Within this level most plnts show n optiml growth when rtionl fertilistion nd liming is pplied. When the mesured vlue of prmeter is higher thn the optiml level, the fertilistion cn be reduced. When the mesured vlue of prmeter is below the optiml level, the fertilistion needs to be incresed in order to hve n economiclly optiml yield. It needs to be noted tht the soil fertility clsses depend on soil texture nd soil orgnic crbon. This mens tht the optiml level is unique for ech prcel. Tble 6 illustrtes the soil fertility clsses for ph-kcl for rble lnd on different soil textures. The optiml level for ph-kcl is different for ech soil texture nd is lower on sndy soils thn on soils contining lom nd cly. The soil fertility clsses for ph-kcl for grsslnd re shown in Tble 7. In Annex 1, the soil fertility clsses for the different prmeters re listed for both rble lnd nd grsslnd. 27

30 Tble 6: Soil fertility clsses for ph-kcl for rble lnd, depending on the soil texture (only vlid with norml crbon levels). ph-kcl Clss Snd Sndy lom Lom Polder Strongly cid < 4. < 4.5 < 5. < 5.5 Low Rther low Optiml level Rther high High Very high > 6.8 > 7.4 > 8. > 8.1 Tble 7: Soil fertility clsses for ph-kcl for grsslnd, depending on the different soil textures (only vlid with norml crbon levels). ph-kcl Clss Snd Sndy lom - Lom Polder Strongly cid < 4.4 < 4.6 < 4.9 Low Rther low Optiml level Rther high High Very high > 6.4 > 7. > Fertilistion nd liming dvice The fertilistion nd liming dvice, bsed on the stndrd soil nlysis, is formulted for rottion of 3 cultivted crops (or 3 growing sesons for perennil crops). In order to clculte the fertilistion nd liming dvice, decision support expert system is developed by SSB, clled BEMEX (BEMEstingsEXpertsysteem) (Geypens et l., 1989; Vndendriessche et l., 1996). The fertilistion nd liming dvice is highly dependent on the cultivted crop for the next 3 growing sesons. Fertilistion is necessry to rech economicl optiml yields nd to prevent nutrient depletion. The fertilistion dvice does not depend on the fct if prcel is under derogtion or no derogtion. The liming dvice, clculted by BEMEX, is bsed on the ph-kcl of the stndrd soil smple, soil texture, orgnic mtter content nd the sensitivity of the cultivted crop for liming. Depending on the cultivted crop, liming my be prtitioned over 3 yers. An ccurte nitrogen fertilistion dvice is formulted with the N-INDEX expert system, provided by SSB (Geypens et l., 1994) (see chpter 4). It is importnt to note tht the fertilistion dvice provided by BEMEX 28

31 is bsed on economicl optimums, nd tht mximl fertilistion limits s defined by the government re not tken into ccount. Also, the fertilistion levels s dvised by the stndrd soil nlysis re bsed on effective nutrient levels. If orgnic fertilisers re used, only prt of the orgnic fertiliser will be vilble to the cultivted crop during the first yer fter ppliction. Annex 2 shows n exmple of report from stndrd soil nlysis of prcel 2 of the monitoring network. The first pge shows the mesured vlues for ech prmeter nd the soil fertility clss for ech prmeter mesured on tht specific prcel. The next pges give the fertilistion nd liming dvice for the different cultivted crops. The result of the stndrd soil smple is determined by the history of the prcel. As such, no sttisticl nlysis between derogtion nd no derogtion prcels ws conducted nd only verge, minimum nd mximum re shown. In the next tbles, only 186 of the 216 prcels re shown. Since some prcels were lredy fertilised when the soil smple ws tken, these results were discrded Stndrd soil smple for grsslnd in spring 212 In Tble 8 the results of the stndrd soil smple for ph-kcl, %C nd phosphorus (P-AL) in spring 212 re shown. These re the verge numbers for the different prcels of the monitoring network, cultivted with grss in 212. Tble 8: Averge ph-kcl, %C nd P-AL mesured in the stndrd soil smple (-6 cm) for derogtion nd no derogtion cultivted with grsslnd in 212. The number of prcels is indicted by n. Derogtion (min, mx) No derogtion (min, mx) n ph-kcl 5.7 (4.2, 7.4) 5.7 (4.5, 7.6) %C 2.8 (1.1, 6.5) 2.7 (1., 4.9) P-AL (mg P/1 g dry soil) 32 (8, 68) 3 (6, 51) Tble 9 shows the percentge of prcels cultivted with grss in the different soil fertility clsses. For the ph-kcl mesured on the prcels cultivted with grsslnd, 5. % of the derogtion prcels nd 55. % of the no derogtion prcels rech the optiml level. 29

32 For crbon 43.5 % of the prcels cultivted with grss on derogtion prcels rech the optiml level. For no derogtion prcels, this is only 37.5 % % of derogtion prcels nd 27.5 % of no derogtion prcels re chrcterized by low level of crbon. Prcels with percentge crbon below optimum hve lower minerlistion nd need more nutrient input. Tble 9: Percentge of prcels grsslnd in the different soil fertility clsses for ph-kcl, %C nd P-AL. Dt re bsed on stndrd soil nlysis in 212. ph-kcl %C P-AL No No No Derogtion Derogtion Derogtion Clss derogtion derogtion derogtion Very low Low Rther low Optiml level Rther high High Very high For phosphorus 21.7 % of the derogtion prcels nd 7.5 % of the no derogtion prcels rech the optiml level % of derogtion nd 75. % of no derogtion prcels hve phosphorus level bove the optiml level. For these prcels it is possible to cultivte crops with lower input for the prmeter phosphorus. However, when the vlue of prmeter reches the optiml level bseline fertilistion is still necessry (in order to prevent tht levels of nutrients, ph nd crbon drop below the optiml level). The verge fertilistion dvice for ll grss prcels for the growing seson 212 is shown in Tble 1. Tble 1: Averge phosphorus (P 2O 5) fertilistion dvice* for the growing seson 212, depending on the soil fertility clss, for the prcels grsslnd in the monitoring network. P 2 O 5 dvice (kg/h) Clss Derogtion No derogtion Very low - 11 Low Rther low Optiml level Rther high High Very high *Fertilistion dvice for grsslnd with grzing cttle. For grsslnd without grzing cttle higher phosphorus fertilistion dvices re formulted, not comprised in the shown verge phosphorus dvices. 3

33 3.2.2 Stndrd soil smple for rble lnd in spring 212 In Tble 11 the results of the stndrd soil nlysis for ph, %C nd phosphorus (P-AL) in spring 212 re shown. These re the verge numbers for the different prcels rble lnd in Spring 212. The level of crbon is lower for rble lnd thn for grsslnd (Tble 8, Tble 11). Tble 11: Averge ph-kcl, %C nd P-AL mesured in the stndrd soil smple (-23 cm) for rble lnd in spring 212. The number of prcels is indicted by n. Derogtion (min, mx) No derogtion (min, mx) n ph-kcl 5.6 (4.4, 7.) 5.9 (4.2, 7.5) %C 1.8 (.8, 3.4) 1.4 (.6, 3.2) P-AL (mg P/1 g dry soil) 33 (12, 61) 35 (4, 65) In 33.4 % of the derogtion nd 4.2 % of no derogtion prcels the ph-kcl reches the optiml level for crop growth (Tble 12). This is lower frequency thn in grsslnd (Tble 9). Of the derogtion prcels 29.6 nd 14.8 % is chrcterized by ph vlue in the ctegory rther low nd rther high. Of the no derogtion prcels 34.1 nd 14.8 % is chrcterized by ph-kcl vlue in the ctegory rther low nd rther high. Tble 12: Percentge of prcels rble lnd in the different soil fertility clsses for ph-kcl, %C nd P-AL. Dt re bsed on stndrd soil nlysis in spring 212. ph-kcl %C P-AL Clss Derogtion No derogtion Derogtion No derogtion Derogtion No derogtion Very low Low Rther low Optiml level Rther high High Very high For the prmeter %C, more thn hlf (55.6 %) of the prcels rble lnd rech the optiml level for derogtion prcels. For no derogtion prcels, this is only 29.3 % % of the derogtion nd 65.8 % of no derogtion prcels hve %C below optimum. For phosphorus only 11. % of 31

34 the prcels rech the optiml level % of the derogtion prcels nd 86.6 % of no derogtion prcels hve vlue of phosphorus bove the optiml level. However, despite the high levels of phosphorus mesured in the stndrd soil smples, n dditionl P-fertilistion is necessry. The verge fertilistion dvice for rble lnd for the growing seson 212 is shown in Tble 13. The verge dvices in Tble 13 do not tke into ccount the P 2 O 5 fertilistion limits of the Mnure Decree, but re bsed on reserch dt in order to optimise the soil fertility of prcel. Tble 13: Averge phosphorus (P 2O 5) fertilistion dvice for the growing seson 212, depending on the soil fertility clss, for the prcels rble lnd in the monitoring network. P 2 O 5 dvice (kg/h) Clss Derogtion No derogtion Very low - 22 Low - - Rther low Optiml level Rther high High Very high The differences in phosphorus dvice between derogtion nd no derogtion prcels rble lnd re cused by the fct tht on derogtion nd no derogtion prcels different crops re grown. Out of the 35 prcels rble lnd under derogtion in 212 (Tble 4) only 1 prcel ws ment to grow beets. On the rble lnd with no derogtion lso crops with lower need of phosphorus thn mize re grown. Tble 5 shows tht of the 87 prcels rble lnd without derogtion on 1 prcels winter whet will be grown in 212 nd on 17 prcels other crops. The lower need of phosphorus of the winter whet nd the other crops on the no derogtion prcels explins the lower verge phosphorus dvice for the no derogtion prcels. 32

35 4 Prcel chrcteristics bsed on the N-INDEX Nitrte in the soil profile my lech out during winter. In spring, soil smple is tken on the prcels of the monitoring network in order to mesure the mount of nitrte vilble to the crop fter winter. Bsed on the nitrte nd mmoni mesured in the lbortory nd dditionl informtion (cultivted crop, cultivr, orgnic mtter in the soil lyer, cultivted crop in the pst seson, orgnic fertiliser ppliction...) nitrogen fertilistion dvice is formulted for ech prcel. This dvice is clculted by mens of the N-INDEX expert system, developed by SSB (Geypens et l., 1994). N-INDEX clcultes the mount of minerl nitrogen tht is/will become vilble to the cultivted crop during the growing seson. For this expert system, 3 input dt re essentil: the mesured minerl N in the soil smple: soil smple is tken in 3 lyers of 3 cm. For crops with deep root system soil smple is tken from to 9 cm in three lyers (for exmple winter whet). Other crops, like pottoes, hve shllow roots nd only the minerl N in the soil profile from to 6 cm is importnt for the next growing seson. In order to know the distribution of nitrte in the soil profile, ll prcels in the monitoring network re smpled from to 9 cm. One soil smple for ech prcel consists of 15 subsmples. The minerl N is mesured by continuous flow in KCl-extrct. the mount of nitrogen tht will become vilble during the growing seson: in order to clculte this fctor with N-INDEX, some prcel chrcteristics re necessry (percentge crbon, ph, history of the prcel, orgnic fertilistion in the pst, liming ). the mount of nitrogen tht will be lost by leching or suboptiml conditions. After this input, N-INDEX for tht specific prcel is clculted. If the N-INDEX is high, lot of nitrogen will be vilble to the crop during the next growing seson nd the corresponding nitrogen fertilistion dvice will be low. The resulting nitrogen fertilistion dvice is function of the N-INDEX nd the nitrte required by the cultivted crop. This mens dditionl informtion on the next growing seson is necessry (crop, vriety of the crop, griculturl prctice ). A fertilistion dvice by mens of the N-INDEX expert system is lwys the effective mount of nitrogen. 33

36 4.1 N-INDEX for grsslnd in spring 212 For grsslnd the verge fertilistion dvice by mens of N-INDEX re shown in Tble 14 for different soil textures. For ech prcel grsslnd fertilistion dvice is formulted with grzing cttle nd without grzing cttle (= only mowing). Since fter ech hrvest fertilistion will be necessry, the dvices re presented for ech grss cutting s well. When grsslnd is cultivted more intensively (for exmple on derogtion prcels) with more thn 3 grss cuttings, more thn 3 fertilistions will be necessry. In this cse higher totl fertilistion is necessry in order to obtin sufficient crop growth. The first hrvest of the seson requires the highest fertilistion. For grsslnd 34 % of the prcels were chrcterized by n N-INDEX lower thn norml, 28 % norml nd 38 % very low. So for grsslnd the verge N-INDEX of the prcels ws mostly lower thn norml or very low, resulting in high N fertilistion dvice. Derogtion prcels re chrcterized by higher number of cuttings. When n extr cut of grss is hrvested, n extr fertilistion ws crried out. Tble 14: Averge nitrogen (kg N/h) fertilistion dvice for grsslnd under derogtion/no derogtion on different soil textures for the growing seson 212. The dvices re given for different hrvests (cut 1, cut 2 nd cut 3) nd seprtely for grsslnd with or without grzing cttle. The number of prcels is indicted by n. Grsslnd with grzing cttle Derogtion No derogtion n cut 1 cut 2 cut 3 sum n cut 1 cut 2 cut 3 sum Snd Sndy lom Lom Cly All soils Grsslnd without Snd grzing cttle Sndy lom (= mowing) Lom Cly All soils

37 4.2 N-INDEX for rble lnd in spring 212 In Tble 15, the nitrogen dvice is shown for prcels cultivted with mize in spring 212. Sixtyone percent of the mize prcels hve norml N-INDEX nd 33 % lower thn norml. One percent of the mize prcels hs very low N-INDEX nd 5 % hve n N-INDEX higher thn norml. For mize the nitrte fertilistion is mostly pplied before sowing in one frction for the minerl fertilistion nd one frction for the orgnic fertilistion. The verge fertilistion dvice for ll prcels is 147 kg nitrte-n per hectre. Tble 15: Averge nitrogen (kg N/h) fertilistion dvice for prcels cultivted with mize in spring 212. Vlues re given seprtely for derogtion nd no derogtion prcels for different soil textures. The number of prcels is indicted by n. n Derogtion (min, mx) n No derogtion (min, mx) Snd (87, 172) (86, 183) Sndy lom (97, 159) (11, 183) Lom (134, 17) Cly (11, 159) 4 15 (146, 164) All soils (87, 172) (86, 183) Tble 16 shows the fertilistion dvices for winter whet, beets nd pottoes. None of the prcels cultivted with these crops re under derogtion. In winter whet the fertilistion is mostly given in three frctions during the growing seson. This wy high yields re possible without qulity losses. For pottoes fertilistion in 2 frctions is dvised. The dvices re lwys bsed on the potentil yield crop cn obtin nd does not tke into ccount conditions like legl restrictions concerning the mount of orgnic nd minerl fertilistion tht cn be pplied on the prcel. Tble 16: Averge nitrogen fertilistion (kg N/h) dvices for different crops for the growing seson 212. The totl N-fertilistion dvices s well s the different frctions re given. The number of prcels is indicted by n. No derogtion n Frction 1 Frction 2 Frction 3 Winter whet Beets Pottoes

38 4.3 N-INDEX for grsslnd in spring 213 For grsslnd in 213 the verge fertilistion dvice by mens of N-INDEX is shown Tble 17 for different soil textures. For ech prcel grsslnd fertilistion dvice is formulted with grzing cttle nd without grzing cttle (= only mowing). Since fter ech hrvest fertilistion will be necessry, the dvices re presented for ech grss cutting s well. When grsslnd is cultivted more intensively (for exmple on derogtion prcels) with more thn 3 grss cuttings, more thn 3 fertilistions will be necessry. In this cse higher totl fertilistion is necessry in order to obtin sufficient crop growth. The first hrvest of the seson requires the highest fertilistion. For grsslnd, 21 % of the prcels re chrcterized by very low N-INDEX, 43 % hve n N- INDEX lower thn norml, 35 % hve norml N-INDEX nd 1 % is chrcterized by n N- INDEX tht ws higher thn norml. A low N-INDEX mens there is little nitrogen in the soil for uptke by the cultivted crop, nd the minerlistion is expected to be low. Therefore, high nitrogen fertilistion dvice is recommended. Tble 17: Averge nitrogen (kg N/h) fertilistion dvice for grsslnd under derogtion/no derogtion on different soil textures for the growing seson 213. The dvices re given for different hrvests (cut 1, cut 2 nd cut 3) nd seprtely for grsslnd with with or without grzing cttle. The number of prcels is indicted by n. Grsslnd with grzing cttle Derogtion No derogtion n cut 1 cut 2 cut 3 n cut 1 cut 2 cut 3 Snd Sndy lom Lom Cly All soils Grsslnd without Snd grzing cttle Sndy lom (= mowing) Lom Cly All soils

39 4.4 N-INDEX for rble lnd in spring 213 In Tble 18, the nitrogen dvice is shown for prcels cultivted with mize in spring 213. More thn hlf of the mize prcels (56 %) hve norml N-INDEX nd 39 % lower thn norml. Five percent of the mize prcels hs N-INDEX tht is higher thn norml. For mize the nitrte fertilistion is mostly pplied before sowing in one frction for the minerl fertilistion nd one frction for the orgnic fertilistion. The verge fertilistion dvice for ll prcels is 15 kg nitrte-n per hectre. Tble 18: Averge nitrogen (kg N/h) fertilistion dvice for prcels cultivted with mize in spring 213. Vlues re given seprtely for derogtion nd no derogtion prcels for different soil textures. The number of prcels is indicted by n. n Derogtion (min, mx) n No derogtion (min, mx) Snd (127, 174) 2 15 (15, 174) Sndy lom (63, 167) (125, 173) Lom (13, 162) Cly All soils (63, 175) (15, 174) Tble 19 shows the fertilistion dvices for winter whet nd pottoes. None of the prcels cultivted with these crops re under derogtion. In winter whet the fertilistion is mostly given in three frctions during the growing seson. This wy high yields re possible without qulity losses. For pottoes fertilistion in 2 frctions is dvised. The dvices re lwys bsed on the potentil yield of crop nd do not tke into ccount conditions like legl restrictions concerning the mount of orgnic nd minerl fertilistion tht cn be pplied on the prcel. Tble 19: Averge nitrogen fertilistion (kg N/h) dvices for different crops for the growing seson 213. The totl N-fertilistion dvices s well s the different frctions re given. The number of prcels is indicted by n. No derogtion n Frction 1 Frction 2 Frction 3 Winter whet Pottoes

40 4.5 N-INDEX for grsslnd in spring 214 For grsslnd in 214 the verge fertilistion dvice by mens of N-INDEX is shown in Tble 2 for different soil textures. For ech prcel grsslnd fertilistion dvice is formulted with grzing cttle nd without grzing cttle (= only mowing). Since fter ech hrvest fertilistion will be necessry, the dvices re presented for ech grss cutting s well. When grsslnd is cultivted more intensively (for exmple on derogtion prcels) with more thn 3 grss cuttings, more thn 3 fertilistions will be necessry. In this cse higher totl fertilistion is necessry in order to obtin sufficient crop growth. The first hrvest of the seson requires the highest fertilistion. For grsslnd, 27 % of the prcels re chrcterized by very low N-INDEX, 38 % hve n N- INDEX lower thn norml nd 35% hve norml N-INDEX. A low N-INDEX mens there is little nitrogen in the soil for uptke by the cultivted crop, nd the minerlistion is expected to be low. Therefore, high nitrogen fertilistion dvice is recommended. Tble 2: Averge nitrogen (kg N/h) fertilistion dvice for grsslnd under derogtion/no derogtion on different soil textures for the growing seson 214. The dvices re given for different hrvests (cut 1, cut 2 nd cut 3) nd seprtely for grsslnd with with or without grzing cttle. The number of prcels is indicted by n. Grsslnd with grzing cttle Derogtion No derogtion n cut 1 cut 2 cut 3 n cut 1 cut 2 cut 3 Snd Sndy lom Lom Cly All soils Grsslnd without Snd grzing cttle Sndy lom (= mowing) Lom Cly All soils

41 4.6 N-INDEX for rble lnd in spring 214 The nitrogen dvice for prcels cultivted with mize in 214 is shown in Tble 21. Only 1 % of the mize prcels hs very low N-index, 49 % hve n N-INDEX lower thn norml nd 5 % hve norml N-INDEX. For mize the nitrte fertilistion is mostly pplied before sowing in one frction for the minerl fertilistion nd one frction for the orgnic fertilistion. The verge fertilistion dvice for ll prcels is 157 kg nitrte-n per hectre. Tble 21: Averge nitrogen (kg N/h) fertilistion dvice for prcels cultivted with mize in spring 214. Vlues re given seprtely for derogtion nd no derogtion prcels for different soil textures. The number of prcels is indicted by n. n Derogtion (min, mx) n No derogtion (min, mx) Snd (125, 164) (9, 186) Sndy lom (138, 149) (139, 182) Lom (137, 178) Cly (161, 183) All soils (125, 178) (9, 183) Tble 22 shows the fertilistion dvices for winter whet, beets nd pottoes. One prcel with winter whet will be grown under derogtion. In winter whet the fertilistion is mostly given in three frctions during the growing seson. This wy high yields re possible without qulity losses. For pottoes fertilistion in 2 frctions is dvised. The dvices re lwys bsed on the potentil yield of crop nd do not tke into ccount conditions like legl restrictions concerning the mount of orgnic nd minerl fertilistion tht cn be pplied on the prcel. Tble 22: Averge nitrogen fertilistion (kg N/h) dvices for different crops for the growing seson 214. The totl N-fertilistion dvices s well s the different frctions re given. The number of prcels is indicted by n. n Frction 1 Frction 2 Frction 3 Beets Winter whet - derogtion no derogtion Pottoes

42 5 Fertilistion 5.1 Livestock mnure In order to determine the exct composition of nutrients present in the supplied mnure, livestock mnure is smpled. This wy, the input of nutrients cn be clculted on the prcels. The composition of livestock mnure is highly vrible (Coppens et l., 29) nd depends on the type of niml nd frm (differences in food, storge of the mnure, frm chrcteristics ). Annully, for ech prcel the frmer receives the lbortory results of the mnure smple for the most importnt nutrients. In ddition n dvice concerning the fertilistion vlue of the mnure is provided. In Tble 23, the number of smples tken in 211, 212, 213 nd 214 re shown for the different types of livestock mnure. The mnure dt of 211 re obtined from the former monitoring project (Vndervelpen et l., 211). The nlyses of 211 were used for the fertilistion prctices in 211. Distinction is mde between derogtion nd no derogtion frms. A derogtion frm hs t lest one prcel under derogtion. On some frms of the monitoring network (mostly no derogtion prcels) no mnure ws pplied on prcels nd thus no mnure nlysis ws crried out. Since derogtion is mostly requested by frmers hving diry cows, the mjority of the nlysed mnure for derogtion frms is cttle slurry. Some derogtion frmers (hving t lest 1 derogtion prcel in the monitoring network) pplied no derogtion mnure on no derogtion prcel prticipting in the monitoring network. Tble 23: Number of livestock mnure smples tken in the period from Distinction is mde between derogtion nd no derogtion frms. Cttle Cttle mnure Pig Sows slurry* (solid)* slurry slurry Other Totl 211 Derogtion No derogtion Derogtion No derogtion Derogtion No derogtion Derogtion No derogtion * Livestock mnure tht cn be pplied on derogtion prcels. 4

43 In the Flemish derogtion request, only livestock mnure of cttle, horses, gots, sheep nd, under specific conditions, the liquid frction of pigs mnure seprted from other frctions by physicl nd mechnicl seprtion my be used on derogtion prcels. Tble 23 shows tht frms clssified s derogtion frm lso hve nlyses of no derogtion mnure. Since derogtion frm is defined s frm which hs 1 or more prcels under derogtion, these frms my hve one or more prcels in the monitoring network which is under no derogtion. The verge vlues of the most importnt nutrients re listed in Tble 24, Tble 26, Tble 28 nd Tble 3. Becuse the mjority of the smples re tken from cttle slurry, the verge composition of cttle slurry is given seprtely for derogtion nd no derogtion frms (Tble 25, Tble 27, Tble 29, Tble 31). Bsed on one-wy ANOVA (p.5) on the log-trnsformed dt, there is no significnt difference in composition of cttle slurry between derogtion nd no derogtion frms for none of the yers. Averge chrcteristics re compred with the dt from the Mestwegwijzer (Coppens et l., 29). There ws lrge stndrd devition for ech prmeter nd for ll types of livestock mnure. 41

44 Tble 24: Averge chrcteristics of different types of livestock mnure to be used for fertilistion during the monitoring project in 211. Vlues re given in kg/1 kg mnure. The number of smples is indicted by n. Averge numbers, bsed on mnure nlysis by the Soil Service of Belgium until 27, re indicted s well (Coppens et l., 29) Mnure n Dry mtter Orgnic mtter N Tot N Min P 2 O 5 K 2 O MgO CO N 2 O C/N Cttle slurry (Stndrd devition) - (19.51) (15.52) (.83) (.64) (.44) (1.4) (.31) (.63) (.37) (1.73) (Averge) - (85.7) (63.7) (5.2) (2.9) (1.5) (4.8) (1.) (1.5) (.7) - Cttle mnure (solid) (Stndrd devition) - (4.61) (29.13) (1.55) (.7) (.78) (2.78) (.48) (1.76) (.51) (3.11) (Averge) - (242.) (184.) (8.5) (2.7) (4.) (8.1) (1.8) (5.) (1.) - Pigs slurry (Stndrd devition) - (2.19) (14.84) (1.81) (1.8) (1.13) (1.47) (.54) (2.16) (.49) (1.14) (Averge) - (82.6) (55.8) (8.6) (5.5) (4.2) (4.8) (1.7) (3.3) (1.3) - Sows slurry (Stndrd devition) - (25.7) (19.26) (1.46) (.6) (1.3) (1.35) (.58) (1.27) (.35) (1.62) (Averge) - (51.8) (34.3) (5.) (3.2) (3.2) (2.8) (1.2) (2.6) (.9) - Other (Stndrd devition) - (1.16) (73.7) (1.34) (1.27) (.74) (2.93) (.29) (1.75) (.64) (12.65) Tble 25: Averge chrcteristics together with stndrd devition of cttle slurry to be used for fertilistion in 211. Vlues re given in kg/1 kg mnure. The number of smples is indicted by n. n Dry mtter Orgnic mtter N Tot N Min P 2 O 5 K 2 O MgO CO N 2 O C/N Derogtion (Stndrd devition) - (18.18) (14.39) (.8) (.68) (.51) (.96) (.32) (.67) (.42) (1.73) No derogtion (Stndrd devition) - (2.9) (16.65) (.85) (.25) (.32) (1.17) (.31) (.58) (.29) (1.76) 42

45 Tble 26: Averge chrcteristics of different types of livestock mnure to be used for fertilistion during the monitoring project in 212. Vlues re given in kg/1 kg mnure. The number of smples is indicted by n. Averge numbers, bsed on mnure nlysis by the Soil Service of Belgium until 27, re indicted s well (Coppens et l., 29). Mnure n Dry mtter Orgnic mtter N Tot N Min P 2 O 5 K 2 O MgO CO N 2 O C/N Cttle slurry (Stndrd devition) - (27.22) (18.98) (.74) (.46) (.39) (1.7) (.4) (1.21) (.45) (2.21) (Averge) - (85.7) (63.7) (5.2) (2.9) (1.5) (4.8) (1.) (1.5) (.7) - Cttle mnure (solid) (Stndrd devition) - (68.76) (16.13) (1.2) (.28) (1.5) (2.) (.77) (2.15) (.43) (4.32) (Averge) - (242.) (184.) (8.5) (2.7) (4.) (8.1) (1.8) (5.) (1.) - Pigs slurry (Stndrd devition) - (15.35) (12.53) (1.85) (1.31) (1.49) (1.87) (.65) (1.9) (.53) (1.27) (Averge) - (82.6) (55.8) (8.6) (5.5) (4.2) (4.8) (1.7) (3.3) (1.3) - Sows slurry (Stndrd devition) - (22.75) (17.48) (.8) (.37) (1.54) (1.17) (.57) (1.42) (.21) (1.88) (Averge) - (51.8) (34.3) (5.) (3.2) (3.2) (2.8) (1.2) (2.6) (.9) - Other (Stndrd devition) - (12.56) (84.15) (2.87) (1.29) (1.65) (4.16) (1.25) (4.82) (2.14) (5.4) Tble 27: Averge chrcteristics together with stndrd devition of cttle slurry to be used for fertilistion in 212. Vlues re given in kg/1 kg mnure. The number of smples is indicted by n. A one-wy ANOVA ws crried out on the log-trnsformed dt (p.5). n Dry mtter Orgnic mtter N Tot N Min P 2 O 5 K 2 O MgO CO N 2 O C/N Derogtion (Stndrd devition) - (3.82) (2.42) (.71) (.47) (.33) (1.8) (.33) (1.32) (.44) (2.6) No derogtion (Stndrd devition) - (2.94) (16.54) (.78) (.45) (.47) (1.5) (.47) (1.4) (.46) (1.4) p-vlue

46 Tble 28: Averge chrcteristics of different types of livestock mnure to be used for fertilistion during the monitoring project in 213. Vlues re given in kg/1 kg mnure. The number of smples is indicted by n. Averge numbers, bsed on mnure nlysis by the Soil Service of Belgium until 27, re indicted s well (Coppens et l., 29). Mnure n Dry mtter Orgnic mtter N Tot N Min P 2 O 5 K 2 O MgO CO N 2 O C/N Cttle slurry Stndrd devition (Averge) - (85.7) (63.7) (5.2) (2.9) (1.5) (4.8) (1.) (1.5) (.7) - Cttle mnure (solid) Stndrd devition (Averge) - (242.) (184.) (8.5) (2.7) (4.) (8.1) (1.8) (5.) (1.) - Pigs slurry Stndrd devition (Averge) - (82.6) (55.8) (8.6) (5.5) (4.2) (4.8) (1.7) (3.3) (1.3) - Sows slurry Stndrd devition (Averge) - (51.8) (34.3) (5.) (3.2) (3.2) (2.8) (1.2) (2.6) (.9) - Other Stndrd devition Tble 29: Averge chrcteristics together with stndrd devition of cttle slurry to be used for fertilistion in 213. Vlues re given in kg/1 kg mnure. The number of smples is indicted by n. n Dry mtter Orgnic mtter N Tot N Min P 2 O 5 K 2 O MgO CO N 2 O C/N Derogtion (Stndrd devition) - (16.96) (14.14) (.65) (.43) (.31) (.71) (.3) (.54) (.32) (1.94) No derogtion (Stndrd devition) - (23.34) (17.69) (1.11) (.66) (.51) (1.41) (.29) (.49) (.3) (2.63) 44

47 Tble 3: Averge chrcteristics of different types of livestock mnure to be used for fertilistion during the monitoring project in 214. Vlues re given in kg/1 kg mnure. The number of smples is indicted by n. Averge numbers, bsed on mnure nlysis by the Soil Service of Belgium until 27, re indicted s well (Coppens et l., 29). Mnure n Dry mtter Orgnic mtter N Tot N Min P 2 O 5 K 2 O MgO CO N 2 O C/N Cttle slurry Stndrd devition (Averge) - (85.7) (63.7) (5.2) (2.9) (1.5) (4.8) (1.) (1.5) (.7) - Cttle mnure (solid) Stndrd devition (Averge) - (242.) (184.) (8.5) (2.7) (4.) (8.1) (1.8) (5.) (1.) - Pigs slurry Stndrd devition (Averge) - (82.6) (55.8) (8.6) (5.5) (4.2) (4.8) (1.7) (3.3) (1.3) - Sows slurry Stndrd devition (Averge) - (51.8) (34.3) (5.) (3.2) (3.2) (2.8) (1.2) (2.6) (.9) - Other Stndrd devition Tble 31: Averge chrcteristics together with stndrd devition of cttle slurry to be used for fertilistion in 214. Vlues re given in kg/1 kg mnure. The number of smples is indicted by n. n Dry mtter Orgnic mtter N Tot N Min P 2 O 5 K 2 O MgO CO N 2 O C/N Derogtion 56 88,24 63,96 3,94 2,14 1,4 4,18 1,5 2,14,77 9,57 (Stndrd devition) - (3,11) (15,36) (,83) (,69) (,4) (,97) (,3) (1,85) (,33) (2,11) No derogtion 56 79,87 59,73 3,44 1,88 1,19 3,72,82 1,67,66 1,32 (Stndrd devition) - (2,82) (16,2) (,89) (,44) (,31) (1,1) (,28) (1,47) (,35) (2,67) 45

48 Percentge of smples Percentge of smples In order to illustrte the importnce of mnure smpling, the vrition on the different cttle slurry smples is shown in Figure 2, Figure 3, Figure 4 nd Figure 5. About 83 % of the mnure smples hd totl N between 3 nd 5 kg/1 kg cttle slurry in 211. This number ws 85 % in 212 nd 76 % in 213 nd 214. If the N in the cttle slurry is higher s expected, frmers risk to fertilise too much, with incresing risks of high nitrte residues before winter period. If the N in cttle slurry is lower s expected, frmers will fertilise too little, resulting in low yields Totl N (kg/1 kg) in cttle slurry Figure 2: Histogrm of the mount of totl N (kg/1 kg product) for the different smples tken from cttle slurry in 211 in the monitoring network Totl N (kg/1 kg) in cttle slurry Figure 3: Histogrm of the mount of totl N (kg/1 kg product) for the different smples tken from cttle slurry in 212 in the monitoring network. 46

49 Percentge of smples Percentge of smples Totl N (kg/1 kg) in cttle slurry Figure 4: Histogrm of the mount of totl N (kg/1 kg product) for the different smples tken from cttle slurry in 213 in the monitoring network Totl N (kg/1 kg) in cttle slurry Figure 5: Histogrm of the mount of totl N (kg/1 kg product) for the different smples tken from cttle slurry in 214 in the monitoring network. 47

50 5.2 Amount of supplied nutrients Nutrients re mostly pplied on the prcels by mens of fertilistion. Different types of fertilistion re possible: minerl fertilistion, ppliction of orgnic fertilisers or orgnic input by grzing cttle. The mounts of supplied nutrients shown re reduced with losses by emission of mmoni during the moment of fertilistion. This fctor is only importnt for the orgnic fertilistion nd is function of the fertiliser ppliction. The used emission losses re shown in Tble 32. The emission of grzing cttle is clculted by mens of Normen en richtwrden 211, vilble on Tble 32: Emission fctors (NH 3-N) s % of the minerl N of the pplied mnure for rble lnd nd grsslnd for different techniques nd mnure types. NH 3 -N emission fctor (% of N minerl pplied) Slurry Arble lnd Injection 1 Spreding + incorportion within 2 hours 21 Grsslnd Injection 2 Triling hoses 35 Solid mnure + incorportion within 24 hours 23 For grzing cttle, n emission fctor of 8 % from the totl mnure-n production during grzing is used The different nutrient inputs on the prcels of the monitoring network in 211 re listed in Tble 33. On most prcels phosphorus fertilistion ws not pplied by mens of minerl fertilisers, which coincides with the governmentl regultions nd limittions. When compring the minerl nd totl fertilistion on grsslnd nd mize between derogtion nd no derogtion prcels, the totl N-fertilistion from orgnic mnure is higher on derogtion prcels. Since on derogtion prcels more cuts of grss re hrvested, more nutrients re removed from the prcels. For derogtion prcels cultivted with mize n dditionl cut of grss is hrvested. This dditionl cut requires nutrients s well. 48

51 Tble 33: Averge nutrient (totl N nd totl P 2O 5 in kg/h) input for derogtion nd no derogtion prcels by fertilistion on the prcels in 211. Vlues re given seprtely for the different cultivted crops. Distinction is mde between totl fertilistion, minerl fertilistion, orgnic fertilistion nd orgnic fertilistion by grzing cttle. The emission losses during fertilistion re lredy subtrcted. Nutrient input Minerl Orgnic Grzing cttle Totl orgnic Totl input N P 2 O 5 N P 2 O 5 N P 2 O 5 N P 2 O 5 N P 2 O 5 Derogtion prcels Grss, grzing cttle Grss, only mowing Mize nd 1 grss cutting Beets Winter whet No derogtion prcels Grss Mize Beets Winter whet Pottoes The verge nutrient input for derogtion nd no derogtion prcels by fertilistion, shown in Tble 34, re the mounts of supplied nutrients reduced with losses by emission of mmoni during the moment of fertilistion. On most prcels phosphorus fertilistion ws not pplied by mens of minerl fertilisers, which coincides with the governmentl regultions nd limittions. On grss prcels more fertilistion, both minerl nd orgnic, is pplied on derogtion prcels. On mize prcels, the difference in totl N-input between derogtion nd no derogtion prcels is more limited. The pplied mount minerl N is bout 5 kg N/h t both types of prcels. The difference of orgnic N between derogtion nd no derogtion prcels cultivted with mize ws limited to 23 kg N/h in

52 Tble 34: Averge nutrient (totl N nd totl P 2O 5 in kg/h) input for derogtion nd no derogtion prcels by fertilistion on the prcels in 212. Vlues re given seprtely for the different cultivted crops. Distinction is mde between totl fertilistion, orgnic fertilistion nd orgnic fertilistion by grzing cttle. The emission losses during fertilistion re lredy subtrcted. Nutrient input Minerl Orgnic Grzing cttle Totl orgnic Totl input N P 2 O 5 N P 2 O 5 N P 2 O 5 N P 2 O 5 N P 2 O 5 Derogtion prcels Grss, grzing cttle Grss, only mowing Mize nd 1 grss cutting Beets Winter whet No derogtion prcels Grss Mize Beets Winter whet Pottoes The verge nutrient input for derogtion nd no derogtion prcels by fertilistion, shown in Tble 35, re the mounts of supplied nutrients reduced with losses by emission of mmoni during the moment of fertilistion. For grss prcels the conclusion cn be the sme s in 211 nd 212. On derogtion prcels clerly more fertilistion is pplied, both minerl nd orgnic. This coincides with the more intensive cultivtion of these prcels. For mize prcels the difference in fertilistion between derogtion nd no derogtion prcels were lrger thn in 211 nd 212. On derogtion prcels 254 kg totl N/h is pplied while 189 kg totl N/h on no derogtion prcels. The difference results from higher input of orgnic mnure (s ment by derogtion). Both on derogtion nd no derogtion prcels fertilistion limits re mostly respected. 5

53 Tble 35: Averge nutrient (totl N nd totl P 2O 5 in kg/h) input for derogtion nd no derogtion prcels by fertilistion on the prcels in 213. Vlues re given seprtely for the different cultivted crops. Distinction is mde between totl fertilistion, minerl fertilistion, orgnic fertilistion nd orgnic fertilistion by grzing cttle. The emission losses during fertilistion re lredy subtrcted. Nutrient input Minerl Orgnic Grzing cttle Totl orgnic Totl input N P 2 O 5 N P 2 O 5 N P 2 O 5 N P 2 O 5 N P 2 O 5 Derogtion prcels Grss, grzing cttle Grss, only mowing Mize nd 1 grss cutting Beets Winter whet No derogtion prcels Grss Mize Beets Winter whet Pottoes The verge nutrient input for derogtion nd no derogtion prcels by fertilistion, shown in Tble 36, re the mounts of supplied nutrients reduced with losses by emission of mmoni during the moment of fertilistion. On derogtion prcels clerly more fertilistion is pplied, both minerl nd orgnic. The difference is pproximtely 1 kg N/h. This coincides often with the more intensive cultivtion of these prcels. The difference in totl nitrogen fertilistion between derogtion nd no derogtion mize prcels ws comprble to the difference in 213. On derogtion prcels 241 kg totl N/h is pplied while 186 kg totl N/h on no derogtion prcels. The difference results from higher input of orgnic mnure (s ment by derogtion). Both on derogtion nd no derogtion prcels fertilistion limits re mostly respected. 51

54 Tble 36: Averge nutrient (totl N nd totl P 2O 5 in kg/h) input for derogtion nd no derogtion prcels by fertilistion on the prcels in 214. Vlues re given seprtely for the different cultivted crops. Distinction is mde between totl fertilistion, minerl fertilistion, orgnic fertilistion nd orgnic fertilistion by grzing cttle. The emission losses during fertilistion re lredy subtrcted. Nutrient input Minerl Orgnic Grzing cttle Totl orgnic Totl input N P 2 O 5 N P 2 O 5 N P 2 O 5 N P 2 O 5 N P 2 O 5 Derogtion prcels Grss, grzing cttle Grss, only mowing Mize nd 1 grss cutting Beets Winter whet No derogtion prcels Grss Mize Beets Winter whet Pottoes Fertilistion prctices It is lso interesting to look t the different fertilistion prctices between derogtion nd no derogtion prcels. A prmeter of interest is the dte of fertilistion, especilly the dte of the first nd the lst fertilistion Figure 6 to Figure 9 show the percentge of prcels fertilised the first nd lst time in prticulr month in 211, seprtely for grss, mize, derogtion nd no derogtion prcels. Percentges re clculted seprtely for minerl nd orgnic fertilistion by dividing the number of prcels with first/lst fertilistion in specific month by the totl number of prcels for combintion of derogtion-crop. The orgnic fertilistion of grzing cttle (mnure) is not tken into ccount. It needs to be noted tht some mize prcels re only fertilised once, so tht the dte of first fertilistion equls the dte of lst fertilistion. In generl, the results of 211 re comprble to the results of 29 nd 21 (Vndervelpen et l., 211). Figure 6 shows the percentge of grss prcels fertilised the first time in prticulr month. More thn hlf of the derogtion prcels (53 %) nd no derogtion prcels (54 %) re fertilised for the 52

55 first time in Mrch with orgnic fertilisers. When it comes to minerl fertilistion, bout 63 % of the derogtion prcels nd 52 % of no derogtion prcels re fertilised for the first time in Mrch Percentge of grss prcels with first fertilistion in specific month of 211, Orgnic fertilisers Derogtion prcels No derogtion prcels Percentge of grss prcels with first fertilistion in specific month of 211, Minerl fertilisers Derogtion prcels No derogtion prcels Figure 6: Percentge of grss prcels with first fertilistion with orgnic fertilisers (bove) or minerl fertilisers (below) in specific month of 211, for derogtion nd no derogtion prcels. Figure 7 shows the percentge of mize prcels fertilised the first time in prticulr month. A lrge mjority of the no derogtion prcels received orgnic fertilisers for the first time in April (74 %), wheres for derogtion prcels the first orgnic fertilistion minly occurs in My (46 %), followed by April (32 %). 53

56 However, when pplying minerl fertilisers, 32 % of the mize derogtion prcels re fertilised for the first time in Mrch nd 57 % in My. This erly fertilistion on derogtion prcels is destined for the grss present on these mize prcels, since grss before mize is derogtion condition. In April, 69 % of the no derogtion prcels re fertilised for the first time with minerl fertilisers Percentge of mize prcels with first fertilistion in specific month of 211, Orgnic fertilisers Derogtion prcels No derogtion prcels Percentge of mize prcels with first fertilistion in specific month of 211, Minerl fertilisers Derogtion prcels No derogtion prcels Figure 7: Percentge of mize prcels with first fertilistion with orgnic fertilisers (bove) or minerl fertilisers (below) in specific month of 211, for derogtion nd no derogtion prcels. 54

57 Figure 8 shows the percentge of grss prcels receiving finl orgnic or minerl fertilistion in prticulr month. Thirty-five percent of the derogtion prcels receive the finl orgnic fertilistion in August. For no derogtion prcels, in August only 8 % of the no derogtion prcels receive finl orgnic fertilistion. Generlly the finl orgnic fertilistion on no derogtion prcels occurs erlier (from Februry until July). For derogtion prcels cultivted with grss, finl minerl fertilistion occurs on 33 % of the prcels in June nd on 36 % of the prcels in July. On no derogtion prcels, 48 % of the prcels re fertilised for the lst time in July. On 19 % of derogtion nd 23 % of no derogtion prcels, finl minerl fertilistion occurs in August Percentge of grss prcels with finl fertilistion in specific month of 211, Orgnic fertilisers Derogtion prcels No derogtion prcels Percentge of grss prcels with finl fertilistion in specific month of 211, Minerl fertilisers Derogtion prcels No derogtion prcels Figure 8: Percentge of grss prcels with finl fertilistion with orgnic fertilisers (bove) or minerl fertilisers (below) in specific month of 211, for derogtion nd no derogtion prcels. 55

58 Figure 9 shows the percentge of mize prcels receiving finl fertilistion in prticulr month. On no derogtion prcels, the finl ppliction of orgnic fertilisers occurs erlier thn on derogtion prcels: 69 % of the no derogtion prcels re fertilised for the lst time in April, wheres 53 % of the derogtion prcels re fertilised for the lst time in My Percentge of mize prcels with finl fertilistion in specific month of 211, Orgnic fertilisers Derogtion prcels No derogtion prcels Percentge of mize prcels with finl fertilistion in specific month of 211, Minerl fertilisers Derogtion prcels No derogtion prcels Figure 9: Percentge of mize prcels with finl fertilistion with orgnic fertilisers (bove) or minerl fertilisers (below) in specific month of 211, for derogtion nd no derogtion prcels. 56

59 The sme cn be seen for the minerl fertilistion: 68 % of the no derogtion prcels re fertilised for the lst time in April, wheres 67 % of the derogtion prcels re fertilised in My. Mize on derogtion prcels is sown lter thn on no derogtion prcels since one cut of grsslnd needs to be hrvested on the derogtion prcels before mize is sown. This cut of grsslnd is not present on no derogtion prcels, therefore the fertilistion on no derogtion prcels cultivted with mize is concentrted in April Figure 1 to Figure 13 show the percentge of prcels fertilised the first nd lst time in prticulr month in 212, seprtely for prcels cultivted with grss or mize on derogtion or no derogtion prcels. The orgnic fertilistion of grzing cttle is not tken into ccount. On prcels which re only fertilised once, the dte of the first nd lst fertilistion re equl. In generl, the results re comprble to 29, 21 (Vndervelpen et l., 211) nd 211. Figure 1 shows the percentge of grss prcels fertilised the first time in prticulr month in 212. Most of the derogtion prcels (58 %) nd no derogtion prcels (5 %) re fertilised for the first time in Mrch with orgnic fertilisers. When it comes to minerl fertilistion, bout 7 % of the derogtion prcels nd 5 % of no derogtion prcels re fertilised for the first time in Mrch. Figure 11 shows the percentge of mize prcels fertilised the first time in prticulr month. Forty-six percent of no derogtion prcels received orgnic fertilisers for the first time in April nd 4 % in My, wheres for derogtion prcels the first orgnic fertilistion minly occurs in My (47 %), followed by Mrch (27 %). 57

60 Percentge of grss prcels with first fertilistion in specific month of 212, Orgnic fertilisers Derogtion prcels No derogtion prcels Percentge of grss prcels with first fertilistion in specific month of 212, Minerl fertilisers Derogtion prcels No derogtion prcels Figure 1: Percentge of grss prcels with first fertilistion with orgnic fertilisers (bove) or minerl fertilisers (below) in specific month of 212, for derogtion nd no derogtion prcels. 58

61 Percentge of mize prcels with first fertilistion in specific month of 212, Orgnic fertilisers Derogtion prcels No derogtion prcels Percentge of mize prcels with first fertilistion in specific month of 212, Minerl fertilisers Derogtion prcels No derogtion prcels Figure 11: Percentge of mize prcels with first fertilistion with orgnic fertilisers (bove) or minerl fertilisers (below) in specific month of 212, for derogtion nd no derogtion prcels. However, when pplying minerl fertilisers, 37 % of the mize derogtion prcels re fertilised for the first time in Mrch nd 33 % in My. This erly fertilistion on derogtion prcels is destined for the grss present on these mize prcels, since grss before mize is derogtion condition. In My, 56 % of the no derogtion prcels re fertilised for the first time with minerl fertilisers. 59

62 Figure 12 shows the percentge of grss prcels receiving finl orgnic or minerl fertilistion in 212 in prticulr month. Thirty-three percent of the derogtion prcels receive the finl orgnic fertilistion in July nd 27 % in August. For no derogtion prcels, 31 % receive the finl orgnic fertilistion in July nd 13 % in August. For derogtion prcels cultivted with grss, finl minerl fertilistion occurs on 25 % of the prcels in July nd 24 % of the prcels in June. On no derogtion prcels, 26 % of the prcels hve finl minerl fertilistion in April nd 2 % in July nd August Percentge of grss prcels with finl fertilistion in specific month of 212, Orgnic fertilisers Derogtion prcels No derogtion prcels Percentge of grss prcels with finl fertilistion in specific month of 212, Minerl fertilisers Derogtion prcels No derogtion prcels Figure 12: Percentge of grss prcels with finl fertilistion with orgnic fertilisers (bove) or minerl fertilisers (below) in specific month of 212, for derogtion nd no derogtion prcels. 6

63 Figure 13 shows the percentge of mize prcels receiving finl fertilistion in prticulr month. On no derogtion prcels, the finl ppliction of orgnic fertilisers occurs erlier thn on derogtion prcels: 42 % of the no derogtion prcels re fertilised for the lst time in April nd 51 % in My, wheres 8 % of the derogtion prcels re fertilised for the lst time in My. Fifty percent of the derogtion prcels nd 58 % of the no derogtion prcels re fertilised for the lst time in My with minerl fertilisers Percentge of mize prcels with finl fertilistion in specific month of 212, Orgnic fertilisers Derogtion prcels No derogtion prcels Percentge of mize prcels with finl fertilistion in specific month of 212, Minerl fertilisers Derogtion prcels No derogtion prcels Figure 13: Percentge of mize prcels with finl fertilistion with orgnic fertilisers (bove) or minerl fertilisers (below) in specific month of 212, for derogtion nd no derogtion prcels. 61

64 5.3.3 Comprison Grss prcels, first fertilistion The percentge of grss prcels with first fertilistion in specific month of 211 nd 212 is more or less the sme: for orgnic fertilisers on derogtion nd no derogtion prcels, most of the prcels re fertilised for the first time in Mrch, followed by Februry, wheres for the minerl fertilizer ppliction on derogtion nd no derogtion prcels most of the prcels re fertilised for the first time in Mrch, followed by My. Grss prcels, finl fertilistion The percentge of grss prcels under derogtion with finl orgnic fertilistion in specific month of 211 nd 212 is more or less the sme: for both yers July nd August. When looking t the finl minerl fertilistion on grss prcels under derogtion, most of the prcels in 211 hd finl minerl fertilistion in June to August, whether in 212 it is spred more evenly over the different months. The percentge of grss prcels under no derogtion with finl orgnic fertilistion is spred for the different months in 211, whether for 212 most of the no derogtion prcels received this in July. When looking t the minerl fertilistion, most of the prcels re fertilised for the lst time in 211 in July, whether in 212 it is spred over the different months, with slight peks in April, July nd August. Mize prcels, first fertilistion The percentge of mize prcels under derogtion with first orgnic fertilistion in specific month in 211 is mostly situted in My, followed by April. In 212, this tkes smll shift, from My, followed by Mrch. When looking t the minerl fertilistion, most of the derogtion prcels re fertilised for the first time in My in 211, where for 212 they re mostly fertilised in Mrch, followed by My nd April. This mens in 211 there were some very specific fertilistion peks, where in 212 minerl fertilistion ws more spred over different months. The percentge of mize prcels under no derogtion with first orgnic fertilistion in specific month in 211 is minly situted in April. In 212, this ws more spred between April nd My. 62

65 For the minerl fertilistion in 211, most of the prcels re fertilised in April, where in 212 it is executed in My. Mize prcels, finl fertilistion For mize prcels under derogtion, finl orgnic fertilistion occurred minly in My in 211 (followed by April) wheres in % is fertilised in My. Finl minerl fertilistion in 211 nd 212 on derogtion prcels occurred in My. Mize prcels under no derogtion were minly fertilised with orgnic or minerl fertilisers in April in 211, wheres in 212 it ws spred over My nd April. 5.4 Fertilistion prctices It is interesting to verify if the lst six yers n evolution exists in fertilistion prctices for prcels cultivted with grss or mize under derogtion or no derogtion. In Tble 37 the mximum fertilistion levels s defined by the government re shown. These levels re bsed on the system of totl nitrogen. One of the most importnt chnges from to is tht since 211 distinction ws mde between grss prcels with only mowing nd grss prcels with mowing nd grzing. For mize prcels with no cut of grss (no derogtion) the mximum input of minerl fertilisers on sndy soil chnged from 15 to 35 kg N/h/yer in nd on no sndy soil from 15 to 5 kg N/h/yer in

66 Tble 37: Mximum fertilistion limits (kg N/h/yer) s defined by the government from (source: Orgnic N Minerl N Totl N Orgnic N Minerl N Totl N All soils Snd No snd Snd No snd All soils Snd No snd Snd No snd Derogtion Grss, only mowing Grss, mowing + grzing Grss + Mize No derogtion Grss, only mowing Grss, mowing + grzing Grss + Mize Mize

67 kg N/h kg N/h Figure 14 shows the verge orgnic (no emission losses during fertilistion tken into ccount) nd minerl N fertilistion for the prcels cultivted with grss under derogtion. The verge orgnic N fertilistion is rther stble lst 4 yers on derogtion prcels cultivted with grss. The orgnic N fertilistion on derogtion prcels with grss rnged in verge between 219 nd 232 kg N/h in the period The totl N fertilistion rnged from 364 to 379 kg N/h in the period Grss prcels, derogtion N minerl N orgnic Figure 14: Averge orgnic nd minerl N fertilistion (kg/h/yer) for derogtion prcels cultivted with grss in the monitoring network (29-214) Grss prcels, no derogtion N minerl 15 N orgnic Figure 15: Averge orgnic nd minerl N fertilistion (kg/h/yer) for no derogtion prcels cultivted with grss in the monitoring network (29-214). 65

68 kg N/h On grss prcels without derogtion (Figure 15) the verge orgnic N fertilistion exceeded the mximl level (17 kg N/h/yer from orgnic mnure) in 29. In 21, 211 nd 212 the verge orgnic N fertiliztion ws ner to the mximl orgnic N fertilistion limit. Minerl N fertilistion tended to decrese on derogtion grss prcels in the period In 213 orgnic N fertilistion exceeded the mximum level while the minerl N fertilistion ws t the sme level s the yers before. The verge orgnic N fertilistion on no derogtion prcels cultivted with grss in the period ws most limited in 214. Only 14 kg N/h ws pplied by orgnic mnure. The minerl fertilistion in 214 on the contrry, ws the highest out of the lst six yers. Nevertheless the fertilistion stndrds were respected. Figure 16 shows the verge orgnic (no emission losses during fertilistion tken into ccount) nd minerl N fertilistion for the prcels cultivted with mize under derogtion. The orgnic N fertilistion on derogtion prcels with mize incresed in the period with mximum in 211 ner to the fertilistion limits s defined by the government (25 kg N/h/yer from orgnic mnure). In the period the verge orgnic N fertiliztion is lower nd rnges from 193 to 27 kg N/h/yer. The verge mount of minerl N supplied vries between 48 nd 62 kg N/h/yer Mize prcels, derogtion N minerl N orgnic Figure 16: Averge orgnic nd minerl N fertilistion (kg/h/yer) for derogtion prcels cultivted with mize in the monitoring network (29-214). On the prcels cultivted with mize without derogtion (Figure 17) the minerl N fertilistion is lmost the sme s on the derogtion prcels. The verge orgnic N fertilistion is since 21 beneth the mximum fertilistion level of 17 kg N/h/yer from orgnic mnure. In 213 nd 66

69 kg N/h 214 only 16 kg orgnic N/h ws pplied. The verge totl N fertilistion on the no derogtion prcels with mize seemed to be reduced slightly since 29. Mize prcels, no derogtion N minerl N orgnic Figure 17: Averge orgnic nd minerl N fertilistion (kg/h/yer) for no derogtion prcels cultivted with mize in the monitoring network (29-214). 5.5 Conclusion The composition of niml mnure is highly vrible. So it is importnt to obtin mnure smple from ll frms in the monitoring network. This lrge vrince is lso shown in Vndervelpen et l. (211) for niml mnure smples in 21 nd 211. More minerl nd orgnic fertilistion is pplied on derogtion thn on no derogtion prcels. This is the most explicit on prcels cultivted with grss. On derogtion prcels cultivted with grss, more grss cuts re removed, wheres on derogtion prcels cultivted with mize grss cut is hrvested before the mize is sown (derogtion condition). Derogtion prcels cultivted with mize receive minerl fertilisers erlier thn no derogtion prcels cultivted with mize. This fertilistion is for the grss present on the prcel. Since the mize is sown lter thn on no derogtion prcels (becuse of the grss present before mize), mize on derogtion prcels receives finl fertilistion lter thn no derogtion prcels. Derogtion prcels cultivted with grss receive both orgnic nd minerl fertilisers lter thn no derogtion prcels cultivted with grss. 67

70 6 Nitrte in the soil profile A soil smple is tken in order to mesure nitrte in the soil profile on ll prcels of the monitoring network t two different moments during the yer: between October 1 st nd November 15 th nd in Februry-April. As such, the evolution of the mount of nitrte nd the distribution of nitrte in the soil profile cn be monitored. Nitrte in the soil profile is ffected by different soil processes. During winter little nitrte is tken up by crops nd leching my occur. The dt were log-trnsformed in order to require homogeneity of the dt ( condition necessry to pply ANOVA, p.5). The dt re visully represented using box plots nd br grphs. The box plots contin the men, stndrd devition nd the stndrd error of the men. The stndrd devition is clculted s: s =[ (x i m) 2 /(n-1)] 1/2 = SD where m is the smple men n is the smple size The stndrd error of the men is the theoreticl stndrd devition of ll smple mens of size n from popultion. SE= s / m where s is the stndrd devition m is the smple men An overview of wether nd climte conditions is given in Annex 3. These figures nd vlues cn explin evolutions of nitrte in the soil s seen t the different smpling moments. 68

71 6.1 Nitrte in utumn 211 Between October 1 st nd November 15 th soil smples were tken. In these soil smples the mount of nitrte in the soil profile from to 3, 3 to 6 cm nd 6 to 9 cm ws mesured, in order to determine the nitrte residue. During winter there is little nitrte uptke by crops nd leching my occur. It is thus very importnt to investigte possible differences in nitrte residue before winter between derogtion nd no derogtion prcels. In the next prgrphs, box plot shows the vrition of the groups (derogtion nd no derogtion). The dt were log-trnsformed in order to obtin normlity of the dtset. All dt re shown visully in br grphs, which show the distribution of nitrte in the soil profile (-3 cm, 3-6 cm, 6-9 cm). The results of homogeneous groups re nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Four prcels with extreme nitrte levels (rnging from 341 to 54 kg N/h) re considered sttisticl outliers nd re excluded for further sttisticl nlysis. Two out of the 3 sttisticl outliers were grsslnd in the pst nd were trnsformed into croplnd. These sttisticl outliers re vlues tht re common in prctice, but were eliminted for the sttisticl nlysis of the dt. The 2 remining prcels detected s outliers were cultivted with vegetbles, culiflower (48 kg N/h) nd spinch (374 kg N/h). It is not uncommon tht the nitrte residue is high on prcels cultivted with vegetbles. The verge nitrte in the soil profile for ech soil lyer nd for different combintions of crop, soil texture nd derogtion is shown in Tble 38. The vlues in bold re verge nitrte residues lrger thn 9 kg NO 3 -N/h. However, since 211 the llowed mximum nitrte residue in the soil profile from -9 cm depends on the cultivted crop, soil type, focus or non-focus re 1. Therefore, the vlues in bold in Tble 38 (> 9 kg NO 3 -N/h) re indictive. On the prcel cultivted with winter whet on cly soil without derogtion, no cover crop ws sown fter hrvest, which resulted in high nitrte residue of 14 kg N/h. The prcel on cly soil cultivted with other crops, ws cultivted with pottoes. Also on lom soil the other crops were pottoes, resulting in nitrte residues of 98 nd 265 kg N/h

72 Tble 38: Averge nitrte-n (kg/h) in the soil profile (-9 cm) nd for ech soil lyer (-3 cm, 3-6 cm, 6-9 cm) for the different combintions of crop, soil texture nd derogtion in utumn 211. The number of prcels is indicted by n. Numbers in bold hve nitrte-n (-9 cm) lrger thn 9 kg N/h. Soil Crop 211 n Nitrte-N (kg/h) -3 cm 3-6 cm 6-9 cm -9 cm Derogtion 85 Cly Beets Grss Mize Winter whet Lom Beets Grss Mize Winter whet Snd Beets Grss Mize Winter whet Sndy lom Beets Grss Mize Winter whet No Derogtion 132 Cly Beets Grss Mize Winter whet Other Lom Beets Grss Mize Winter whet Other Snd Beets Grss Mize Winter whet Other Sndy lom Beets Grss Mize Winter whet Other

73 Tble 39 shows the verge nitrte-n in the soil profile nd for ech soil lyer for grss with 1-3 cuttings or 4-7 cuttings nd for silge nd grin mize. Tble 39: Averge nitrte-n (kg/h) in the soil profile (-9 cm) nd for ech soil lyer (-3 cm, 3-6 cm, 6-9 cm) for grss nd mize in utumn 211. The number of prcels is indicted by n. Nitrte-N (kg/h) n -3 cm 3-6 cm 6-9 cm -9 cm Grss, 1-3 grss cuttings Derogtion No derogtion Grss, 4-7 grss cuttings Derogtion No derogtion Silge mize Derogtion No derogtion Grin mize Derogtion No derogtion All crops on ll soil textures First, the comprison is mde between derogtion nd no derogtion prcels for ll crops on ll soil textures. For both derogtion nd no derogtion prcels, lrge vrition in nitrte mesurements is observed (Figure 18), rnging from 5 to 269 kg N/h in derogtion prcels nd from 5 to 265 kg N/h in no derogtion prcels. 2.6 All crops on ll soil textures log(nitrte) Derogtion J derogtion No derogtion N Men Men±SE Men±2*SD Figure 18: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for ll crops on ll soil textures in utumn 211. SE: stndrd error of the men. SD: stndrd devition. 71

74 Nitrte-N (kg/h) The verge nitrte-n is 74 (± 54) kg N/h for derogtion prcels nd 84 (± 62) kg N/h for no derogtion prcels (Figure 19). Most of the nitrte cn be found in the upper soil lyer (-3 cm). Since no derogtion crops (vegetbles,...) re present in this dtset, the compred groups re not homogeneous nd no sttisticl nlysis ws conducted between derogtion nd no derogtion prcels. The little rinfll in utumn 211 ws lso responsible for the lower mounts of nitrte in the soil lyer 6-9 cm (Figure 244) Derogtion No derogtion -3 cm 3-6 cm 6-9 cm Figure 19: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 211 for ll crops on ll soil textures Derogtion crops on ll soil textures The further nlysis is limited to prcels with derogtion crops (mize, grss, beets nd winter whet) only. There is lrge vrince for derogtion nd no derogtion prcels (Figure 2) nd no sttisticlly significnt difference (p =.8) cn be found between derogtion (74 ± 54 kg N/h) nd no derogtion prcels (76 ± 57 kg N/h) (Figure 21). Nitrte in the first (-3 cm) soil lyer cn lech out to the next lyer but is still vilble to the cultivted crop. Nitrte in the 6-9 cm soil lyer is not completely vilble for the plnts, so it my lech out to the groundwter during winter. Therefore, with respect to the wter qulity, higher nitrte levels in the upper lyers re more fvourble thn high levels in the deeper soil lyers. Figure 21 demonstrtes tht bout 8 % of the nitrte residue is present in the upper soil lyers (from -3 cm nd 3-6 cm) in both derogtion nd no derogtion prcels cultivted with derogtion crops nd on ll soil textures. 72

75 Nitrte-N (kg/h) 2.6 Derogtion crops on ll soil textures log(nitrte) Derogtion J Vr1 No N derogtion Men Men±SE Men±2*SD Figure 2: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on ll soil textures in utumn 211. SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 21: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels for derogtion crops on ll soil textures in utumn 211. The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. No sttisticlly significnt differences in nitrte residue in utumn 211 re found between derogtion nd no derogtion prcels. Since nitrte residue is influenced by the soil texture, the nitrte residue between derogtion nd no derogtion prcels will be nlysed for specific soil textures. Since derogtion is mostly requested on sndy nd sndy lom soil textures, these soil 73

76 textures re discussed in detil in the following prgrphs. For the other soil textures, the dt re listed in Tble Derogtion crops on sndy soils Derogtion is mostly requested on sndy soils. There is still lrge vrince for the different prcels within one group (Figure 22). No sttisticlly significnt difference cn be found (p =.99) between derogtion (8 ± 59 kg N/h) nd no derogtion prcels (79 ± 6 kg N/h). Becuse of the specific chrcteristics of sndy soil (low wter retention cpcity), the vilble nutrients re very sensitive to leching. Therefore it is importnt to determine in which soil lyer the lrgest mount of nitrte residue is present. Most of the nitrte cn be found in the upper soil lyer (-3 cm), with 38 ± 32 kg N/h in this lyer for derogtion prcels nd 33 ± 28 kg N/h for no derogtion prcels (Figure 23). 2,6 Derogtion crops on sndy soils 2,4 2,2 2, log(nitrte) 1,8 1,6 1,4 1,2 1,,8 Derogtion J Vr1 No Nderogtion Men Men±SE Men±2*SD Figure 22: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on sndy soils in utumn 211. SE: stndrd error of the men. SD: stndrd devition. 74

77 Nitrte-N (kg/h) Derogtion No derogtion -3 cm 3-6 cm 6-9 cm Figure 23: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels for derogtion crops on sndy soils in utumn 211. The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Grss nd mize on sndy soils Except for the soil texture, the nitrte residue is minly relted to the cultivted crop. It is thus interesting to verify if sttisticlly significnt effect exists between derogtion nd no derogtion prcels for specific combintions of soil texture nd cultivted crop. Tble 38 shows tht the mjority of derogtion prcels consists of sndy soil, cultivted with grss or mize. The verge nitrte residue levels re shown in Figure 24. However both grss nd mize prcels re shown on this br grph, the sttisticl nlysis ws conducted seprtely for prcels cultivted with grss or mize. No significnt difference exists between derogtion nd no derogtion prcels cultivted with grss (p =.31) or mize (p =.82) on sndy soils. For prcels cultivted with grss on sndy soils, the derogtion prcels hve nitrte residue of 64 ± 52 kg N/h for derogtion, while the no derogtion prcels hve nitrte residue of 51 ± 51 kg N/h. The derogtion prcels cultivted with mize hve n verge nitrte residue of 18 ± 61 kg N/h versus 112 ± 58 kg N/h for no derogtion prcels cultivted with mize. 75

78 Nitrte-N (kg/h) 12 1 ' ' cm 3-6 cm cm Derogtion No derogtion Grss Derogtion No derogtion Mize Figure 24: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels with grss or mize on sndy soils in utumn 211. The results for grss nd mize were nlysed seprtely. A one-wy ANOVA (p.5) ws conducted on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Derogtion crops on sndy lom soils 2,6 Derogtion crops on sndy lom soils 2,4 2,2 2, log(nitrte) 1,8 1,6 1,4 1,2 1,,8 Derogtion J Vr1 No derogtion N Men Men±SE Men±2*SD Figure 25: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on sndy lom soils in utumn 211. SE: stndrd error of the men. SD: stndrd devition. 76

79 Nitrte-N (kg/h) Derogtion is common on sndy lom soils s well. The verge nitrte residues for derogtion crops on derogtion nd no derogtion prcels on sndy lom soils re shown in Figure 26. There re no significnt differences between derogtion (64 ± 46 kg/h) nd no derogtion (66 ± 45 kg/h) prcels (p =.72). Like on sndy soils the upper soil lyer (-3 cm) contins most of the nitrte. More thn 5 % of the nitrte residue on sndy lom soils in utumn 211 ws situted in the soil lyer -3 cm. The vrition in the nitrte levels is high (Figure 25) cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 26: Averge nitrte-n (kg/h) in derogtion nd no derogtion prcels for derogtion crops on sndy lom soils in utumn 211. The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Grss nd mize on sndy lom soils Since grss nd mize on sndy lom soils re common in the monitoring network, seprte sttisticl nlysis is crried out for these crops (Tble 38). The verge vlues for grss nd mize with nd without derogtion for sndy lom soil re shown in Figure 27. The verge level of nitrte-n for derogtion prcels cultivted with grss is 31 ± 14 kg/h versus 4 ± 18 kg/h for no derogtion prcels. There is no sttisticl difference in nitrte-n level for derogtion nd no derogtion prcels (p =.23). For prcels cultivted with mize there is no sttisticlly significnt difference between derogtion (16 ± 38 kg nitrte-n/h) nd no derogtion (94 ± 56 kg nitrte-n/h) prcels (p =.43). 77

80 Nitrte-N (kg/h) 12 1 ' ' cm 3-6 cm 6-9 cm Derogtion No derogtion Grss Derogtion Mize No derogtion Figure 27: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels with grss or mize on sndy lom soils in utumn 211. The results for grss nd mize were nlysed seprtely. A one-wy ANOVA (p.5) ws conducted on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 6.2 Nitrte in utumn 211, prcels which were continuously under derogtion/no derogtion during In order to verify the long-term impct of derogtion on the nitrte residue in the soil, only the prcels which were continuously under derogtion/no derogtion during were retined for sttisticl nlysis. In the next prgrphs, box plot shows the vrition of the groups (derogtion nd no derogtion). The dt were log-trnsformed in order to obtin normlity of the dtset. All dt re shown visully in br grphs, which show the distribution of nitrte in the soil profile (-3 cm, 3-6 cm, 6-9 cm). The results of homogeneous groups re nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. In Tble 4 the verge nitrte-n (kg/h) in the soil profile in utumn 211 for prcels continuously under derogtion/no derogtion during is shown. The vlues in bold re verge nitrte residues lrger thn 9 kg NO 3 -N/h. However, since 211 the llowed mximum nitrte residue in the soil profile from -9 cm depends on the cultivted crop, soil type, focus or non-focus re. Therefore, the vlues in bold (> 9 kg NO 3 -N/h) re indictive. 78

81 Tble 4: Averge nitrte-n (kg/h) in the soil profile for prcels continuously under derogtion/no derogtion during , in utumn 211. The nitrte-n is given for the different combintions of soil texture, cultivted crop nd derogtion. For ech combintion the totl mount of nitrte is given s well s for ech soil lyer (lyer 1: -3 cm, lyer 2: 3-6 cm nd lyer 3: 6-9 cm). The number of prcels is indicted by n. Soil Crop 211 n Nitrte-N (kg/h) -3 cm 3-6 cm 6-9 cm -9 cm Derogtion 6 Cly Beets Grss Mize Winter whet Lom Beets Grss Mize Winter whet Snd Beets Grss Mize Winter whet Sndy lom Beets Grss Mize Winter whet No derogtion 89 Cly Beets Grss Mize Winter whet Other Lom Beets Grss Mize Winter whet Other Snd Beets Grss Mize Winter whet Other Sndy lom Beets Grss Mize Winter whet Other

82 6.2.1 All crops on ll soil textures From ll prcels, two no derogtion prcels were considered sttisticl outliers (48 nd 54 kg N/h). One prcel ws cultivted with grss nd converted into mize (54 kg N/h), the other prcel ws cultivted with culiflower. Figure 28 shows lrge vrition in nitrte residue for derogtion nd no derogtion prcels. 2.8 All crops on ll soil textures log(nitrte) Derogtion J Vr1 No derogtion N Men Men±SE Men±2*SD Figure 28: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels in utumn 211, for ll crops on ll soil textures including only prcels which were continuously under derogtion/no derogtion during SE: stndrd error of the men. SD: stndrd devition. The verge nitrte-n in derogtion prcels is 76 ± 56 kg N/h nd in no derogtion prcels 87 ± 64 kg N/h (Figure 29). Most of the nitrte is locted in the upper soil lyer (-3 cm). Since no derogtion crops (vegetbles,...) re present in this dtset, the compred groups re not homogeneous nd no sttisticl nlysis ws conducted between derogtion nd no derogtion prcels. 8

83 Nitrte-N (kg/h) cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 29: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 211 for ll crops on ll soil textures, including only prcels which were continuously under derogtion/no derogtion during Derogtion crops on ll soil textures Figure 3 shows lrge vrition in nitrte residue for derogtion nd no derogtion prcels. 2.6 Derogtion crops on ll soil textures log(nitrte) Derogtion J No Nderogtion Men Men±SE Men±2*SD Figure 3: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels in utumn 211, for derogtion crops on ll soil textures, including only prcels which were continuously under derogtion/no derogtion during SE: stndrd error of the men. SD: stndrd devition. 81

84 Nitrte-N (kg/h) There is no significnt (p =.85) difference between the nitrte residue in derogtion prcels (76 ± 56 kg N/h) nd in no derogtion prcels (8 ± 6 kg N/h) (Figure 31). Agin, most of the nitrte is locted in the upper soil lyer (-3 cm) cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 31: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 211 for derogtion crops on ll soil textures, including only prcels which were continuously under derogtion/no derogtion during The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Derogtion crops on sndy soils Figure 32 shows lrge vrition in nitrte residue for derogtion nd no derogtion prcels on sndy soil. The nitrte-n between derogtion prcels (85 ± 61 kg/h) nd no derogtion prcels (84 ± 66 kg/h) is not significntly different (p =.64) (Figure 33). Most of the nitrte is locted in the upper soil lyer (-3 cm). 82

85 Nitrte-N (kg/h) 2,8 Derogtion crops on sndy soils 2,6 2,4 2,2 log(nitrte) 2, 1,8 1,6 1,4 1,2 1,,8 Derogtion J Vr1 No Nderogtion Men Men±SE Men±2*SD Figure 32: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels in utumn 211, for derogtion crops on sndy soils, including only prcels which were continuously under derogtion/no derogtion during SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 33: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 211 for derogtion crops on sndy soils, including only prcels which were continuously under derogtion/no derogtion during The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 83

86 Nitrte-N (kg/h) Grss nd mize on sndy soils The verge nitrte-n on grss prcels under derogtion is 7 ± 5 kg N/h nd 57 ± 56 kg N/h on no derogtion prcels (Figure 34). For mize, the verge nitrte-n under derogtion is 114 ± 62 kg N/h nd 113 ± 68 kg N/h on no derogtion prcels. For both crops on sndy soil, derogtion hs no significnt effect on the nitrte residue (p =.15 for grss prcels nd p =.94 for mize prcels). 12 ' ' cm cm cm Derogtion No derogtion Grss Derogtion Mize No derogtion Figure 34: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 211 for grss nd mize on sndy soils, including only prcels which were continuously under derogtion/no derogtion during The results for grss nd mize were nlysed seprtely. A one-wy ANOVA (p.5) ws conducted on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Sndy lom soils Figure 35 shows lrge vrition in nitrte residue for derogtion nd no derogtion prcels on sndy lom soils. The verge nitrte is 6 ± 47 kg N/h on derogtion prcels nd 73 ± 49 kg N/h on no derogtion prcels. There is no significnt effect of derogtion on the nitrte residue (p =.29) (Figure 36). Most of the nitrte is locted in the upper soil lyer (-3 cm). 84

87 2,6 Derogtion crops on sndy lom soils 2,4 2,2 2, log(nitrte) Nitrte-N (kg/h) 1,8 1,6 1,4 1,2 1,,8 Derogtion J Vr1 No N derogtion Men Men±SE Men±2*SD Figure 35: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels in utumn 211, for derogtion crops on sndy lom, including only prcels which were continuously under derogtion/no derogtion during SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 36: : Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 211 for derogtion crops nd on sndy lom soils, including only prcels which were continuously under derogtion/no derogtion during The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 85

88 Nitrte-N (kg/h) Grss nd mize on sndy lom soils The verge nitrte-n in grss prcels under derogtion is 39 ± 28 kg N/h, in no derogtion prcels this is 43 ± 2 kg N/h (Figure 37). The verge nitrte-n in mize prcels under derogtion is 15 ± 5 kg N/h, in no derogtion prcels 99 ± 53 kg N/h. Most of the nitrte is locted in the upper soil lyer (-3 cm). There is no significnt difference between derogtion nd no derogtion crops cultivted with grss or mize (p =.56 for grss prcels nd p =.83 for mize prcels) ' ' cm 3-6 cm cm Derogtion No derogtion Grss Derogtion Mize No derogtion Figure 37: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 211 for grss nd mize nd on sndy lom soils, including only prcels which were continuously under derogtion/no derogtion during The results for grss nd mize were nlysed seprtely. A one-wy ANOVA (p.5) ws conducted on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 6.3 Nitrte in utumn 211 in the deeper soil lyer For 4 prcels n dditionl soil smple ws tken from 9 to 12 cm (the deep soil smple ). In this soil lyer the mount of nitrte is mesured. Three sttisticl outliers were removed (16.2 kg N/h under derogtion, 86.7 nd 12.9 kg N/h under no derogtion). Dt were considered sttisticl outliers when exceeding the verge plus 2 times the stndrd devition. A significntly (p.5) positive correltion exists between the mount of nitrte present in the soil profile from -9 cm nd the nitrte present in the soil profile from 9-12 cm. This mens tht when the nitrte residue in the -9 cm lyer is high, high nitrte content in the 9-12 cm soil lyer is expected. 86

89 7 Nitrte in the soil profile in utumn 211 Y = *x, R² =.51, p < cm cm Figure 38: Sctterplot of the nitrte-n (kg/h) in the soil profile from -9 cm versus the nitrte-n (kg/h) in the soil profile from 9-12 cm in utumn 211. Since the deep soil smples re tken on selection of prcels it is not possible to crry out sttisticl nlysis for ll combintions of derogtion, soil texture nd cultivted crop. The comprison ws limited to grss nd mize on ll soil textures. The sttisticl nlyses ws conducted on the log-trnsformed dt for grss nd mize seprtely. There is n verge of 3 ± 1 kg nitrte-n/h nd 17 ± 12 kg nitrte-n/h present in the soil lyer from 9-12 cm in prcels cultivted with mize nd grss respectively. There is no sttisticl difference between derogtion nd no derogtion prcels cultivted with grss for the soil lyer from to 12 cm (p =.49) nor for prcels cultivted with mize (p =.58). This is illustrted in Figure 39. The decresing mount of nitrte-n regrding to the deeper soil lyers, ws explined by the little mount of precipittion in utumn 211 (Figure 244). 87

90 Nitrte-N (kg/h) ' ' Derogtion No derogtion Derogtion No derogtion Grss Mize -3 cm 3-6 cm 6-9 cm 9-12 cm Figure 39: Averge nitrte-n (kg/h) in the 4 soil lyers on derogtion nd no derogtion prcels on ll soil textures cultivted with grss or mize in utumn 211. The results for grss nd mize were nlysed seprtely. A one-wy ANOVA (p.5) ws conducted on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 6.4 Nitrte in spring 212 In ech prcel of the monitoring network nitrte smple hs been tken from Februry to April 212. This nitrte smple consists of three soil lyers (-3 cm, 3-6 cm nd 6-9 cm) nd provides informtion on the mount of nitrte in the soil profile fter winter nd the mount vilble to the cultivted crop for the next growing seson. Every frmer receives nitrte fertilistion dvice, bsed on the N-INDEX expert system (Geypens et l., 1994). This dvice is function of the mount of nitrte in the soil profile, the crop (different crops needs different mounts of nutrients nd crops with deeper roots cn tke up nitrte from deeper lyers) nd soil chrcteristics (ph, crbon...). The soil chrcteristics re of gret importnce to estimte the mount of nitrte relesed by minerlistion. The distribution of nitrte in the soil profile is importnt: more nitrte in the top lyer is desirble for good wter qulity, since only few crops re ble to tke up the nitrte from the lyer 6-9 cm. By compring with the nitrte in utumn 211, the nitrte smple in spring 212 is n indiction for the mount of nitrte tht leched out during winter. In the next prgrphs, box plot shows the vrition of the groups (derogtion nd no derogtion). The dt were log-trnsformed in order to obtin normlity of the dtset. All dt re shown visully in br grphs, which show the distribution of nitrte in the soil profile (-3 cm, 3-6 cm, 6-9 cm). The results of homogeneous groups re nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. 88

91 The verge level of nitrte-n mesured in the soil smples in utumn 211 nd spring 212 is shown in Tble 41. The mount of nitrte is given for the combintions of derogtion, soil texture nd cultivted crop for the totl soil profile (-9 cm) nd for ech soil lyer of 3 cm. Only 189 prcels re listed in this tble (insted of 217). Twenty prcels were lredy fertilised when the soil smples were tken. Moreover, only the prcels re shown where there ws no sttisticl outlier present for utumn 211, nor for spring 212. Therefore, vlues in this Tble 41 re not identicl for utumn 211 s shown in Tble 38. The vlues in bold in Tble 41 hve high levels of nitrte (> 9 kg N/h) in utumn 211. However, since 211 the llowed mximum nitrte residue in the soil profile from -9 cm depends on the cultivted crop, soil type, focus or non-focus re. Therefore, the vlues in bold (> 9 kg NO 3 -N/h) re indictive. All these combintions with high nitrte in the soil profile in utumn 211 hd lso high levels of nitrte in the soil during spring 212. The reltion between nitrte-n in the soil profile from -9 cm in utumn 211 nd spring 212 is shown in sctterplot (Figure 4). A significnt correltion (p.5) exists between nitrte in utumn 211 nd spring 212. The model explined 31 % of the vrince. 16 Nitrte in the soil profile in utumn 211 nd spring 212 Y= *x, R² =.31, p <.1 Nitrte-N in spring 212 (kg/h) Nitrte-N in utumn 211 (kg/h) Figure 4: Sctterplot of the nitrte-n (kg/h) in the soil profile from -9 cm in utumn 211 versus the nitrte-n (kg/h) in the soil profile from -9 cm in spring

92 Tble 41: Averge nitrte-n (kg/h) in the soil profile in utumn 211 nd spring 212. The nitrte-n is given for the different combintions of soil texture, cultivted crop nd derogtion in 211. For ech combintion the totl mount of nitrte is given s well s for ech soil lyer (lyer 1: -3 cm, lyer 2: 3-6 cm nd lyer 3: 6-9 cm). The number of prcels is indicted by n. Soil Crop 211 n Autumn 211 Nitrte-N (kg/h) in spring cm -3cm 3-6cm 6-9cm -9cm Derogtion 72 Cly Beets Grss Mize Winter whet Lom Beets Grss Mize Winter whet Snd Beets Grss Mize Winter whet Sndy lom Beets Grss Mize Winter whet No derogtion 117 Cly Beets Grss Mize Winter whet Other Lom Beets Grss Mize Winter whet Other Snd Beets Grss Mize Winter whet Other Sndy lom Beets Grss Mize Winter whet Other

93 6.4.1 All crops on ll soil textures In the first prt of the nlysis, the totl mount of nitrte in spring 212 is compred between derogtion nd no derogtion prcels for ll crops on ll soil textures. On both derogtion nd no derogtion prcels, the nitrte mesurements show lrge vrition (Figure 41). The verge nitrte-n is 44 ± 36 kg/h for derogtion prcels nd 47 ± 39 kg/h for no derogtion prcels. The nitrte in the upper soil lyer (-3 cm) is smll compred to the other soil lyers (Figure 42). Since no derogtion crops (vegetbles,...) re present in this dtset, the compred groups re not homogeneous nd no sttisticl nlysis ws conducted between derogtion nd no derogtion prcels. 2.4 All crops on ll soil textures log(nitrte) Derogtion J Vr1 No Nderogtion Men Men±SE Men±2*SD Figure 41: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels with ll crops on ll soil textures in spring 212. SE: stndrd error of the men. SD: stndrd devition. 91

94 Nitrte-N (kg/h) cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 42: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels with ll crops on ll soil textures in spring Derogtion crops on ll soil textures In next step derogtion nd no derogtion prcels cultivted with only derogtion crops (grss, mize, beets, winter whet) re compred. The mesured nitrte vlues re highly vrible (Figure 43). 2,4 Derogtion crops on ll soil types 2,2 2, 1,8 log(nitrte) 1,6 1,4 1,2 1,,8,6 Derogtion J Vr1 No derogtion N Men Men±SE Men±2*SD Figure 43: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on ll soil textures in spring 212. SE: stndrd error of the men. SD: stndrd devition. 92

95 Nitrte-N (kg/h) No sttisticlly significnt difference ws found between nitrte mesured on derogtion (44 ± 36 kg N/h) nd no derogtion (44 ± 36 kg N/h) prcels (Figure 44, p =.92). The first soil lyer of derogtion prcels contins 29 % of the nitrte from -9 cm, the second lyer 34 % nd the third lyer 37 %. The first soil lyer for no derogtion prcels contins 27 % of the nitrte-n from -9 cm, the second lyer 32 % nd the third lyer 41 % cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 44: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels for derogtion crops on ll soil textures in spring 212. The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Derogtion crops on sndy soils In the next step, differences between derogtion nd no derogtion prcels for the most importnt soil textures nd derogtion crops re explored. Tble 41 shows tht the most dominnt soil texture in the monitoring network is snd. The verge vlue of nitrte-n for derogtion crops on sndy soils is 43 ± 42 kg/h for derogtion prcels nd 42 ± 37 kg/h for no derogtion prcels. The vrition within one group is lrge (Figure 45). The nitrte mesured in sndy soils in derogtion prcels from -9 cm does not differ significntly from the nitrte mesured in no derogtion prcels (Figure 46, p =.77). For the different soil lyers seprtely no significnt effect of derogtion ws found. In ll prcels the lrgest mount of nitrte is present in the soil lyer from 6 to 9 cm. The first soil lyer of derogtion prcels contins 29 % of the nitrte from -9 cm, the second lyer 34 % nd the third lyer 37 %. The first soil lyer of no derogtion prcels contins 26 % of the nitrte-n from -9 cm, the second lyer 31 % nd the third lyer 43 %. 93

96 Nitrte-N (kg/h) 2,4 Derogtion crops on sndy soils 2,2 2, 1,8 log(nitrte) 1,6 1,4 1,2 1,,8,6 Derogtion J Vr1 No Nderogtion Men Men±SE Men±2*SD Figure 45: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on sndy soils in spring 212. SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 46: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels for derogtion crops on sndy soils in spring 212. The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Grss nd mize on sndy soils So fr no significnt differences were found between derogtion nd no derogtion prcels for derogtion crops on sndy soils. Since grss nd mize re mostly cultivted on sndy soils, these combintions re compred sttisticlly (Figure 47). 94

97 Nitrte-N (kg/h) For grss the nitrte-n ws 31 ± 34 kg/h in derogtion prcels nd 36 ± 33 kg/h in no derogtion prcels. There is no significnt difference for nitrte-n in the soil profile between derogtion nd no derogtion prcels cultivted with grss (p =.95). For mize the nitrte-n ws 59 ± 52 kg/h in derogtion prcels nd 49 ± 41 kg/h in no derogtion prcels. There is no significnt difference for nitrte-n in the soil profile between derogtion nd no derogtion prcels cultivted with mize (p =.89) ' ' -3 cm 3-6 cm 6-9 cm Derogtion No derogtion Grss Derogtion No derogtion Mïze Figure 47: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels with grss or mize on sndy soils in spring 212. The results for grss nd mize were nlysed seprtely. A one-wy ANOVA (p.5) ws conducted on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Derogtion crops on sndy lom soils Besides on sndy soils, most of the prcels in the monitoring network re chrcterized by sndy lom soils (Tble 41). In Figure 48 nd Figure 49 the nlysis is crried out for prcels with derogtion crops. On no derogtion prcels on sndy lom soil, lrger vrition ws observed thn on derogtion prcels (Figure 48). No significnt difference ws found between derogtion (39 ± 24 kg N/h) nd no derogtion prcels (43 ± 36 kg N/h) on sndy lom soils (Figure 49, p =.8). Also, for the individul lyers, the mesured nitrte did not differ between derogtion nd no derogtion prcels for the sndy lom soils, with only derogtion crops. 95

98 2,4 Derogtion crops on sndy lom soils 2,2 2, 1,8 log(nitrte) Nitrte-N (kg/h) 1,6 1,4 1,2 1,,8,6,4 Derogtion J Vr1 No derogtion N Men Men±SE Men±2*SD Figure 48: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on sndy lom soils in spring 212. SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 49: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels for derogtion crops on sndy lom soil in spring 212. The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 96

99 Nitrte-N (kg/h) Grss nd mize on sndy lom soils Figure 5 shows the verge vlues of nitrte-n in the totl soil profile nd the different soil lyers for grss nd mize on sndy lom soils. For grss the verge nitrte-n ws 25 ± 13 kg/h in derogtion prcels nd 27 ± 2 kg/h in no derogtion prcels. The lrgest mount of nitrte is present in the upper soil lyer -3 cm (45 % of the nitrte) for prcels cultivted with grss. There is no significnt difference between derogtion nd no derogtion prcels cultivted with grss (p =.57). For mize the verge nitrte level ws 55 ± 22 kg N/h on derogtion prcels nd 61 ± 42 kg N/h on no derogtion prcels (Figure 5). There is no significnt difference between derogtion nd no derogtion prcels cultivted with mize (p =.88) ' ' -3 cm 3-6 cm 6-9 cm Derogtion No derogtion Grss Derogtion No derogtion Mize Figure 5: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels with grss or mize on sndy lom soils in spring 212. The results for grss nd mize were nlysed seprtely. A one-wy ANOVA (p.5) ws conducted on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 97

100 6.5 Nitrte in spring 212, prcels which were continuously under derogtion/no derogtion during All crops on ll soil textures In order to verify the long-term impct of derogtion on the nitrte in the soil spring 212, only the prcels which were continuously under derogtion/no derogtion during were retined for sttisticl nlysis. In the next prgrphs, box plot shows the vrition of the groups (derogtion nd no derogtion). The dt were log-trnsformed in order to obtin normlity of the dtset. All dt re shown visully in br grphs, which show the distribution of nitrte in the soil profile (-3 cm, 3-6 cm, 6-9 cm). The results of homogeneous groups re nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. The vlues in bold in Tble 42 hve high levels of nitrte in utumn 211 (> 9 kg N/h). However, since 211 the llowed mximum nitrte residue in the soil profile from -9 cm depends on the cultivted crop, soil type, focus or non-focus re. Therefore, the vlues in bold (> 9 kg NO 3 -N/h) re indictive. 98

101 Tble 42: Averge nitrte-n (kg/h) in the soil profile in utumn 211 nd spring 212 for prcels continuously under derogtion/no derogtion during The nitrte-n is given for the different combintions of soil texture, cultivted crop nd derogtion. For ech combintion the totl mount of nitrte is given s well s for ech soil lyer. The number of prcels is indicted by n. Soil Crop 211 n Autumn 211 Nitrte-N (kg/h) spring cm -3cm 3-6cm 6-9cm -9cm Derogtion 52 Cly Beets Grss Mize Winter whet Lom Beets Grss Mize Winter whet Snd Beets Grss Mize Winter whet Sndy lom Beets Grss Mize Winter whet No derogtion 71 Cly Beets Grss Mize Winter whet Other Lom Beets Grss Mize Winter whet Other Snd Beets Grss Mize Winter whet Other Sndy lom Beets Grss Mize Winter whet Other

102 On both derogtion nd no derogtion prcels, lrge vrition in nitrte in spring 212 cn be noticed (Figure 51). Since no derogtion crops (vegetbles,...) re present in this dtset, the compred groups re not homogeneous nd no sttisticl nlysis ws conducted between derogtion nd no derogtion prcels. 2.4 All crops on ll soil textures log(nitrte) Nitrte-N (kg/h) Derogtion J Vr1 No N derogtion Men Men±SE Men±2*SD Figure 51: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels on ll soil textures in spring 212, including only prcels which were continuously under derogtion/no derogtion during SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 52: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in spring 212 for ll crops on ll soil textures, including only prcels which were continuously under derogtion/no derogtion during

103 The verge nitrte-n is 45 ± 38 kg/h on derogtion prcels nd 46 ± 37 kg/h on no derogtion prcels (Figure 52). Due to leching fter winter, most of the nitrte is locted in the soil lyer from 6-9 cm Derogtion crops on ll soil textures Figure 53 shows lrge vrition in nitrte in both derogtion nd no derogtion prcels cultivted with derogtion crops. The verge nitrte-n is 45 ± 38 kg/h in derogtion prcels nd 47 ± 37 kg/h in no derogtion prcels. There is no significnt difference between derogtion nd no derogtion prcels (Figure 54, p =.83). Most of the nitrte is locted in the soil lyer from 6-9 cm. 2.4 Derogtion crops on ll soil textures log(nitrte) Derogtion J Vr1 No N derogtion Men Men±SE Men±2*SD Figure 53: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels in spring 212, for derogtion crops on ll soil textures, including only prcels which were continuously under derogtion/no derogtion during SE: stndrd error of the men. SD: stndrd devition. 11

104 Nitrte-N (kg/h) cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 54: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in spring 212 for derogtion crops on ll soil textures, including only prcels which were continuously under derogtion/no derogtion during The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Derogtion crops on sndy soils On both derogtion nd no derogtion prcels cultivted with derogtion crops on sndy soils, lrge vrition in nitrte in spring 212 cn be noticed (Figure 55). 2,4 Derogtion crops on sndy soils 2,2 2, 1,8 log(nitrte) 1,6 1,4 1,2 1,,8,6 Derogtion J Vr1 No derogtion N Men Men±SE Men±2*SD Figure 55: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels in spring 212, for derogtion crops on sndy soils, including only prcels which were continuously under derogtion/no derogtion during SE: stndrd error of the men. SD: stndrd devition. 12

105 Nitrte-N (kg/h) The verge nitrte-n is 46 ± 46 kg/h on derogtion prcels nd 44 ± 38 kg/h on no derogtion prcels. There is no significnt effect of derogtion on nitrte in the soil (-9 cm) in spring 212 (Figure 56, p =.79). Most of the nitrte is locted in the soil lyer from 6-9 cm cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 56: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in spring 212 for derogtion crops on sndy soils, including only prcels which were continuously under derogtion/no derogtion during The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Grss nd mize on sndy soils On sndy soils cultivted with grss, the verge nitrte-n is 38 ± 38 kg/h on derogtion prcels nd 42 ± 39 kg/h on no derogtion prcels. There is no significnt effect of derogtion on the prcels cultivted with grss (p =.86). For mize, the verge nitrte-n is 63 ± 57 kg N/h on derogtion prcels nd 49 ± 4 kg N/h on no derogtion prcels. (Figure 57). There is no significnt effect of derogtion on the prcels cultivted with mize (p =.87). 13

106 Nitrte-N (kg/h) ' ' -3 cm 3-6 cm cm Derogtion No derogtion Grss Derogtion No derogtion Mize Figure 57: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in spring 212 for grss nd mize nd on sndy soils, including only prcels which were continuously under derogtion/no derogtion during The results for grss nd mize were nlysed seprtely. A one-wy ANOVA (p.5) ws conducted on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Derogtion crops on sndy lom soils On sndy lom soils the vrition on no derogtion prcels cultivted with derogtion crops is lrger (Figure 58). 2,6 Derogtion crops on sndy lom soils 2,4 2,2 2, 1,8 log(nitrte) 1,6 1,4 1,2 1,,8,6,4 Derogtion J Vr1 No N derogtion Men Men±SE Men±2*SD Figure 58: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels in spring 212, for derogtion crops on sndy lom soils, including only prcels which were continuously under derogtion/no derogtion during SE: stndrd error of the men. SD: stndrd devition. 14

107 Nitrte-N (kg/h) There is no significnt (p =.62) difference in verge nitrte-n between derogtion (32 ± 17 kg/h) nd no derogtion prcels (49 ± 39 kg/h) (Figure 59) cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 59: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in spring 212 for derogtion crops on sndy lom soils, including only prcels which were continuously under derogtion/no derogtion during The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Grss nd mize on sndy lom soils On sndy lom soils there re only 1 prcels cultivted with grss under derogtion, 7 prcels cultivted with grss under no derogtion, 5 prcels cultivted with mize under derogtion nd 9 prcels cultivted with mize under no derogtion. Due to the smll smple size, no sttisticl nlysis is done. 6.6 Nitrte in spring 212 in the deeper soil lyer In spring 212, 33 prcels were lso smpled from 9 to 12 cm ( deep soil smple ). The objective ws to hve 4 deep soil smples, however 7 prcels were lredy fertilised t the moment of smpling. In this deep soil lyer the mount of nitrte-n is mesured. These deep soil smples re tken simultneously with the nitrte smple (from to 9 cm) fter winter. Dt were considered s sttisticl outlier when exceeding the verge plus 2 times the stndrd devition. Three sttisticl outliers were removed: 186 kg N/h for derogtion prcel cultivted with mize, 161 kg N/h for no derogtion prcel cultivted with mize nd 151 kg N/h for 15

108 Nitrte-N (kg/h) no derogtion prcel cultivted with grss. These prcels with sttisticl outlier of the deeper soil lyer in spring 212 were no sttisticl outliers in utumn 211. The verge nitrte-n of the soil lyer from 9-12 cm for grss prcels under derogtion is 16 ± 14 kg/h nd for prcels with no derogtion 31 ± 24 kg/h. The effect of derogtion is not significnt (p =.19). The verge nitrte-n of the soil lyer from 9-12 cm for mize prcels under derogtion is 52 ± 25 kg/h nd 36 ± 15 kg/h without derogtion. There is no significnt effect of derogtion on the verge nitrte-n of the soil lyer from 9-12 cm for mize prcels (p =.24) (Figure 6). Despite the lck of sttisticl significnt differences between derogtion nd no derogtion prcels, it seems for grss prcels tht the soil lyer 9-12 cm contins less nitrte-n on derogtion prcels thn on no derogtion prcels, whilst on mize prcels the opposite is observed. Most of the nitrte in the soil profile in spring 212 is locted in the soil lyer from 9-12 cm. For grss prcels under derogtion, 4 % of the nitrte in the lyer -12 cm is locted in the soil lyer from 9-12 cm. For grss prcels with no derogtion 51 % of the nitrte in the lyer -12 cm is locted in the soil lyer from 9-12 cm. For mize prcels under derogtion, 53 % of the nitrte in the lyer -12 cm is locted in the soil lyer from 9-12 cm nd for mize prcels with no derogtion 45 %. During winter nitrte moved down (leched) nd deeper soil lyers were enriched regrding the sitution in utumn 211. December 211 ws month with more rinfll s norml (Figure 244) ' ' -3 cm 3-6 cm 6-9 cm 9-12 cm Derogtion No Derogtion No derogtion derogtion Grss Mize Figure 6: Averge nitrte-n (kg/h) in the 4 soil lyers on derogtion nd no derogtion prcels on ll soil textures cultivted with grss or mize in spring 212. The results for grss nd mize were nlysed seprtely. A one-wy ANOVA (p.5) ws conducted on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 16

109 6.7 Nitrte in utumn 212 Between 1 st of October nd 15 th of November, soil smples were tken in order to determine the mount of nitrte in the soil profile from to 3, 3 to 6 nd 6 to 9 cm. In the next prgrphs, box plot shows the vrition of the groups (derogtion nd no derogtion). The dt were log-trnsformed in order to obtin normlity of the dtset. All dt re shown visully in br grphs, which show the distribution of nitrte in the soil profile (-3 cm, 3-6 cm, 6-9 cm). The results of homogeneous groups re nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Ten prcels with nitrte level exceeding the verge plus 2 times the stndrd devition re considered sttisticl outliers nd re excluded for further sttisticl nlysis. These numbers rnge from 166 to 33 kg N/h nd include 5 derogtion nd 5 no derogtion prcels. Three prcels were converted grss prcels, conversion in spring 212 nd cultivtion of mize (33 kg N/h, 24 kg N/h nd 226 kg N/h). One prcel ws cultivted with grss nd turned into mize prcel in spring 211 (296 kg N/h). For 2 prcels cultivted with mize (both 166 kg N/h) lower yield ws mentioned by the frmers. On one prcel sugr beets were cultivted (235 kg N/h) but the yield ws not good, only 6 ton/h. Winter whet ws sown fter hrvest. Time between hrvest nd smpling of nitrte residue ws 1 month. The minor hrvest, the lbour of the soil, the remining crop residues (leves) nd the ppliction of chicken mnure (with rther slow relese) in spring cn be responsible for the high nitrte residue. Another prcel ws fertilised (orgnic nd minerl) in ugust, before plnting the leek, resulting in high residue of 261 kg N/h. The verge nitrte in the soil profile for ech soil lyer nd for different combintions of crop, soil texture nd derogtion is shown in Tble 43. The vlues in bold re verge nitrte residues lrger thn 9 kg NO 3 -N/h. However, since 211 the llowed mximum nitrte residue in the soil profile from -9 cm depends on the cultivted crop, soil type, focus or non-focus re. Therefore, the vlues in bold in Tble 43 (> 9 kg NO 3 -N/h) re indictive. For some prcels cultivted with winter whet the nitrte residue ws high lthough winter whet is crop with lower verge nitrte residue. The nitrte residue on the prcel cultivted with winter whet on lom soil ws 137 kg N/h. The winter whet ws hrvested mid August nd cover crop (Itlin rye-grss) ws sown mid September, but in August solid niml mnure ws pplied (5 ton/h). 17

110 Tble 43: Averge nitrte-n (kg/h) in the soil profile in utumn 212 for prcels under derogtion/no derogtion in 212. The nitrte-n is given for the different combintions of soil texture, cultivted crop nd derogtion. For ech combintion the totl mount of nitrte is given s well s for ech soil lyer. The number of prcels is indicted by n. Soil Crop 212 n Nitrte-N (kg/h) in utumn 212-3cm 3-6cm 6-9cm -9cm Derogtion 87 Cly Beets Grss Mize Winter whet Lom Beets Grss Mize Winter whet Snd Beets Grss Mize Winter whet Sndy lom Beets Grss Mize Winter whet No derogtion 116 Cly Beets Grss Mize Winter whet Other Lom Beets Grss Mize Winter whet Other Snd Beets Grss Mize Winter whet Other Sndy lom Beets Grss Mize Winter whet Other

111 On sndy soil, 4 prcels were cultivted with winter whet. On one prcel no cover crop ws sown (93 kg N/h). On 2 prcels cover crop ws sown nd no fertilistion ws pplied fter hrvest (98 nd 13 kg N/h). On the 4 th prcel (19 kg N/h) white mustrd ws sown s cover crop shortly fter hrvest, but in utumn winter whet ws sown gin. So t time of smpling the nitrte residue (November 2 nd ), minerlistion of white mustrd could be mesured All crops on ll soil textures For derogtion nd no derogtion prcels, lrge vrition in nitrte in the soil profile (-9 cm) is observed (Figure 61), rnging from 5 to 151 kg N/h for derogtion prcels nd 6 to 153 kg N/h for no derogtion prcels. 2.4 All crops on ll soil textures log(nitrte) Derogtion J DA No derogtion N Men Men±SE Men±2*SD Figure 61: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for ll crops on ll soil textures in utumn 212. SE: stndrd error of the men. SD: stndrd devition. The verge nitrte-n is 48 (± 37) kg N/h for derogtion prcels nd 49 (± 34) kg N/h for no derogtion prcels (Figure 62). The mount of nitrte in ech soil lyer is pproximtely equl. Since no derogtion crops (vegetbles,...) re present in this dtset, the compred groups re not homogeneous nd no sttisticl nlysis ws conducted between derogtion nd no derogtion prcels. 19

112 Nitrte-N (kg/h) cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 62: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 212 for ll crops on ll soil textures Derogtion crops on ll soil textures The further nlysis is limited to prcels with derogtion crops (mize, grss, beets nd winter whet) only. 2.4 Derogtion crops on ll soil types log(nitrte) Derogtion J der No derogtion N Men Men±SE Men±2*SD Figure 63: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on ll soil textures in utumn 212. SE: stndrd error of the men. SD: stndrd devition. 11

113 Nitrte-N (kg/h) There is lrge vrince in nitrte in the soil (-9 cm) for derogtion nd no derogtion prcels (Figure 63) nd no sttisticlly significnt difference (p =.91) cn be found between derogtion (48 ± 37 kg N/h) nd no derogtion prcels (49 ± 33 kg N/h) (Figure 64) cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 64: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels for derogtion crops on ll soil textures in utumn 212. The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. The nitrte residue between derogtion nd no derogtion prcels will be sttisticlly nlysed for specific soil textures. Since derogtion is mostly requested on sndy nd sndy lom soil textures, these soil textures re discussed in the following prgrphs. For the other soil textures, the dt re listed in Tble Derogtion crops on sndy soils Derogtion is mostly requested on sndy soils (Tble 43). There is lrge vrince for the different prcels for derogtion nd no derogtion prcels (Figure 65). No sttisticlly significnt difference is found (p =.7) between derogtion (51 ± 38 kg N/h) nd no derogtion prcels (49 ± 36 kg N/h) (Figure 66). The nitrte-n ws more or less eqully distributed over the 3 soil lyers. 111

114 2.4 Derogtion crops on sndy soils log(nitrte) Nitrte-N (kg/h) Derogtion J der No derogtion N Men Men±SE Men±2*SD Figure 65: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on sndy soils in utumn 212. SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 66: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels for derogtion crops on sndy soils in utumn 212. The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 112

115 Nitrte-N (kg/h) Grss nd mize on sndy soils Tble 43 shows tht the mjority of derogtion prcels hve sndy soil nd re cultivted with grss or mize. The verge nitrte residue levels re shown in Figure 67. A sttisticl nlysis ws crried out for grss nd mize seprtely. No significnt differences exist between derogtion nd no derogtion prcels cultivted with grss (p =.23) or mize (p =.36). For prcels cultivted with grss on sndy soils, the derogtion prcels hve nitrte residue of 41 ± 33 kg N/h for derogtion, while the no derogtion prcels hve nitrte residue of 32 ± 23 kg N/h. The derogtion prcels cultivted with mize hve n verge nitrte residue of 68 ± 42 kg N/h versus 57 ± 36 kg N/h for no derogtion prcels cultivted with mize ' ' -3 cm 3-6 cm 6-9 cm 1 Derogtion No derogtion Derogtion No derogtion Grss Mïze Figure 67: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels cultivted with grss or mize on sndy soils in utumn 212. The results for grss nd mize were nlysed seprtely. A one-wy ANOVA (p.5) ws conducted on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Derogtion crops on sndy lom soils Derogtion is common on sndy lom soils s well. The nitrte residue for derogtion crops on sndy lom soils is shown in Figure

116 2.4 Derogtion crops on sndy lom soils log(nitrte) Nitrte-N (kg/h) Derogtion J der No derogtion N Men Men±SE Men±2*SD Figure 68: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on sndy lom soils in utumn 212. SE: stndrd error of the men. SD: stndrd devition. There is no significnt difference between derogtion (42 ± 35 kg/h) nd no derogtion (48 ± 29 kg/h) prcels (p =.53). The vrition in the nitrte levels is high (Figure 68) cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 69: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels for derogtion crops on sndy lom soils in utumn 212. The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 114

117 Nitrte-N (kg/h) Grss nd mize on sndy lom soils Since grss nd mize on sndy lom soils re common combintions in the monitoring network, seprte sttisticl nlysis is crried out. The verge vlues for grss nd mize with nd without derogtion on sndy lom soil re shown in Figure 7. A sttisticl nlysis ws crried out for grss nd mize seprtely. There is no significnt difference between derogtion nd no derogtion prcels cultivted with grss (p =.5) or mize (p =.6). The verge level of nitrte-n for derogtion prcels cultivted with grss is 24 ± 1 kg/h versus 38 ± 22 kg/h for no derogtion prcels. The verge level of nitrte-n for derogtion prcels cultivted with mize is 8 ± 36 kg/h versus 54 ± 3 kg/h for no derogtion prcels ' ' -3 cm 3-6 cm 6-9 cm 1 Derogtion No derogtion Derogtion No derogtion Grss Mïze Figure 7: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels cultivted with grss or mize on sndy lom soils in utumn 212. The results for grss nd mize were nlysed seprtely. A one-wy ANOVA (p.5) ws conducted on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 115

118 6.8 Nitrte in utumn 212, prcels which were continuously under derogtion/no derogtion during In order to verify the long-term impct of derogtion on the nitrte residue in the soil, only the prcels which were continuously under derogtion/no derogtion during were retined for sttisticl nlysis. In the next prgrphs, box plot shows the vrition of the groups (derogtion nd no derogtion). The dt were log-trnsformed in order to obtin normlity of the dtset. All dt re shown visully in br grphs, which show the distribution of nitrte in the soil profile (-3 cm, 3-6 cm, 6-9 cm). The results of homogeneous groups re nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. In Tble 44, the verge nitrte-n (kg/h) in the soil profile for prcels continuously under derogtion/no derogtion is shown. The vlues in bold re verge nitrte residues lrger thn 9 kg NO 3 -N/h. However, since 211 the llowed mximum nitrte residue in the soil profile from -9 cm depends on the cultivted crop, soil type, focus or non-focus re. Therefore, the vlues in bold in the tble (> 9 kg NO 3 -N/h) re indictive. 116

119 Tble 44: Averge nitrte-n (kg/h) in the soil profile for prcels continuously under derogtion/no derogtion during , in utumn 212. The nitrte-n is given for the different combintions of soil texture, cultivted crop nd derogtion. For ech combintion the totl mount of nitrte is given s well s for ech soil lyer (lyer 1: -3 cm, lyer 2: 3-6 cm nd lyer 3: 6-9 cm). The number of prcels is indicted by n. Soil Crop 212 n Nitrte-N (kg/h) -3 cm 3-6 cm 6-9 cm -9 cm Derogtion 55 Cly Beets Grss Mize Winter whet Lom Beets Grss Mize Winter whet Snd Beets Grss Mize Winter whet Sndy lom Beets Grss Mize Winter whet No derogtion 86 Cly Beets Grss Mize Winter whet Other Lom Beets Grss Mize Winter whet Other Snd Beets Grss Mize Winter whet Other Sndy lom Beets Grss Mize Winter whet Other

120 6.8.1 All crops on ll soil textures Figure 71 shows lrge vrition in nitrte residue for long-term derogtion nd no derogtion prcels. 2.4 All crops on ll soil textures log(nitrte) Nitrte-N (kg/h) Derogtion J der No Nderogtion Men Men±SE Men±2*SD Figure 71: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels in utumn 212, for ll crops on ll soil textures including only prcels which were continuously under derogtion/no derogtion during SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 72: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 212 for ll crops on ll soil textures, including only prcels which were continuously under derogtion/no derogtion during

121 The verge nitrte-n on derogtion prcels is 47 ± 35 kg/h nd on no derogtion prcels 5 ± 34 kg N/h (Figure 72). Since no derogtion crops (vegetbles,...) re present in this dtset, the compred groups re not homogeneous nd no sttisticl nlysis ws conducted between derogtion nd no derogtion prcels Derogtion crops on ll soil textures Figure 73 shows lrge vrition in nitrte residue for derogtion nd no derogtion prcels. There is no significnt (p =.72) difference between the nitrte residue on derogtion prcels (47 ± 35 kg N/h) nd no derogtion prcels (49 ± 32 kg N/h) (Figure 74). 2.4 Derogtion crops on ll soil textures log(nitrte) Derogtion J der No derogtion N Men Men±SE Men±2*SD Figure 73: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels in utumn 212, for derogtion crops on ll soil textures, including only prcels which were continuously under derogtion/no derogtion during SE: stndrd error of the men. SD: stndrd devition. 119

122 Nitrte-N (kg/h) cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 74: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 212 for derogtion crops nd soil textures, including only prcels which were continuously under derogtion/no derogtion during The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Derogtion crops on sndy soils Figure 75 shows lrge vrition in nitrte residue for derogtion nd no derogtion prcels on sndy soil. The nitrte-n between derogtion prcels (54 ± 38 kg/h) nd no derogtion prcels (5 ± 35 kg/h) is not significntly different (p =.57) (Figure 76). 2.4 Derogtion crops on sndy soils log(nitrte) Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 75: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels in utumn 212, for derogtion crops on sndy soils, including only prcels which were continuously under derogtion/no derogtion during SE: stndrd error of the men. SD: stndrd devition. 12

123 Nitrte-N (kg/h) Nitrte-N (kg/h) cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 76: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 212 for derogtion crops nd on sndy soils, including only prcels which were continuously under derogtion/no derogtion during The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Grss nd mize on sndy soils The verge nitrte on grss prcels under derogtion is 4 ± 26 kg N/h nd 35 ± 9 kg N/h on no derogtion prcels (Figure 77). For mize, the verge nitrte-n under derogtion is 83 ± 42 kg/h nd 53 ± 34 kg/h on no derogtion prcels. There is no significnt difference between derogtion nd no derogtion prcels cultivted with grss (p =.42) or mize (p =.7) ' ' -3 cm 3-6 cm cm Derogtion No derogtion Grss Derogtion Mize No derogtion Figure 77: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 212 for grss nd mize on sndy soils, including only prcels which were continuously under derogtion/no derogtion during The results for grss nd mize were nlysed seprtely. A one-wy ANOVA (p.5) ws conducted on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 121

124 6.8.4 Derogtion crops on sndy lom soils Figure 78 shows lrge vrition in nitrte residue for derogtion crops on sndy lom soils. The verge nitrte is 38 ± 34 kg N/h on derogtion prcels nd 49 ± 31 kg/h on no derogtion prcels (Figure 79). There is no significnt effect of derogtion on the nitrte residue (p =.15) 2.4 Derogtion crops on sndy lom soils log(nitrte) Nitrte-N (kg/h) Derogtion J No N derogtion Men Men±SE Men±2*SD Figure 78: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels in utumn 212, for derogtion crops on sndy lom, including only prcels which were continuously under derogtion/no derogtion during SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 79: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 212 for derogtion crops nd on sndy lom soils, including only prcels which were continuously under derogtion/no derogtion during The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 122

125 Nitrte-N (kg/h) Grss nd mize on sndy lom soils On sndy lom soils, there is no significnt difference in nitrte residue between derogtion nd no derogtion prcels cultivted with grss (p =.9) or mize prcels (p =.31). The verge nitrte-n on grss prcels under derogtion is 23 ± 9 kg/h, on no derogtion prcels this is 38 ± 24 kg/h (Figure 8). The verge nitrte-n on mize prcels under derogtion is 79 ± 45 kg/h, on no derogtion prcels 57 ± 32 kg/h. Most of the nitrte is locted in the upper soil lyer (- 3 cm) ' ' -3 cm cm 6-9 cm Derogtion No derogtion Grss Derogtion Mize No derogtion Figure 8: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 212 for grss nd mize nd on sndy lom soils, including only prcels which were continuously under derogtion/no derogtion during The results for grss nd mize were nlysed seprtely. A one-wy ANOVA (p.5) ws conducted on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 6.9 Nitrte in utumn 212 in the deeper soil lyer For 4 prcels n dditionl soil smple ws tken from 9 to 12 cm (the deep soil smple ). In this soil lyer the mount of nitrte is mesured. Dt were considered sttisticl outliers when exceeding the verge plus 2 times the stndrd devition. Two sttisticl outliers were removed (486 kg N/h nd 448 kg N/h for -12 cm, both no derogtion prcels). For one prcel the mount of nitrte-n in the deeper soil lyer (9-12 cm) (152 kg N/h) nd the nitrte residue in the soil lyer from to 9 cm in utumn 212 (296 kg N/h) ws detected s sttisticl outlier. This prcel ws converted from grss prcel into rble prcel in spring 211. On the other prcel (352 kg N/h; 9-12 cm) pottoes were grown nd hrvested erly in July. Pottoes re crop 123

126 9-12 cm with often high nitrte residue but especilly becuse of the erly dte of hrvest lrger mount of nitrte-n in the soil profile ws possible since there ws long time of minerlistion without nutrient uptke. After removing the sttisticl outliers the dtset still contined some high nitrte vlues (Figure 81) nd no significnt correltion (p =.43) is found between the mount of nitrte present in the soil profile from -9 cm nd the nitrte present in the soil profile from 9-12 cm. The lrge nitrte vlues present in the grph re no sttisticl outliers but the grph shows tht they influence strongly the reltion between the mount of nitrte present in the soil profile from -9 cm nd the nitrte present in the soil profile from 9-12 cm. When removing the 3 prcels with high nitrte vlues in the soil lyer -9 cm or 9-12 cm (filled dots on the grph), the mount of nitrte present in the soil profile from -9 cm nd the nitrte present in the soil profile from 9-12 cm were significntly correlted (p.5) (Figure 81). 14 Nitrte in the soil profile in utumn Y = *x R² =.68; p= Y = *x R² =.2; p= cm Figure 81: Sctterplot of the nitrte-n (kg/h) in the soil profile from -9 cm versus the nitrte-n (kg/h) in the soil profile from 9-12 cm in utumn 212. Solid line=reltion bsed on ll mesurements; dshed line= trendline bsed on the dtset of not filled dots. 124

127 Nitrte-N (kg/h) The filled dots with high mount of nitrte-n in the soil lyer 9-12 cm were prcel cultivted with spinch followed by leek nd grss prcel which ws mowed begin October but grss ws left on the prcel. The deep soil smples re tken on selection of prcels. Therefore it is not possible to crry out sttisticl nlysis for ll combintions of derogtion, soil texture nd cultivted crop. The comprison ws limited to grss nd mize on ll soil textures. The sttisticl nlysis ws conducted for grss nd mize seprtely. No significnt difference ws found between derogtion nd no derogtion prcels in the soil lyer from 9 to 12 cm for grss (p =.23) or mize (p =.76). There is lso no significnt difference between derogtion nd no derogtion prcels in the soil lyer from -12 cm for grss (p =.43) or mize (p =.29). The verge level of nitrte-n in prcels cultivted with grss for the soil lyer -12 cm under derogtion is 6 ± 43 kg/h nd under no derogtion 44 ± 32 kg/h. The verge level of nitrte-n in prcels cultivted with mize for the soil lyer -12 cm under derogtion is 92 ± 79 kg/h nd 59 ± 24 under no derogtion ' ' -3 cm 3-6 cm 6-9 cm 9-12 cm Derogtion No derogtion Grss Derogtion No derogtion Mize Figure 82: Averge nitrte-n (kg/h) in the 4 soil lyers on derogtion nd no derogtion prcels on ll soil textures cultivted with grss or mize, utumn 212. The results for grss nd mize were nlysed seprtely. A one-wy ANOVA (p.5) ws conducted on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 125

128 6.1 Nitrte in spring 213 As in spring 212, t ech prcel of the monitoring network nitrte smple hs been tken from Februry to April 213. This nitrte smple consists of three soil lyers (-3 cm, 3-6 cm nd 6-9 cm) nd provides informtion on the mount of nitrte in the soil profile fter winter nd the mount vilble to the cultivted crop for the next growing seson. Every frmer receives nitrte fertilistion dvice, bsed on the N-INDEX expert system (Geypens et l., 1994). Comprison of the nitrte in utumn 212 nd the nitrte smple in spring 213, gives n indiction of the mount of nitrte tht leched out during winter. In the next prgrphs, box plot shows the vrition of the groups (derogtion nd no derogtion). The dt were log-trnsformed in order to obtin normlity of the dtset. All dt re shown visully in br grphs, which show the distribution of nitrte in the soil profile (-3 cm, 3-6 cm, 6-9 cm). The results of homogeneous groups re nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. The verge level of nitrte-n mesured in the soil smples in utumn 212 nd spring 213 is shown in Tble 45. The mount of nitrte is given for the combintions of derogtion, soil texture nd cultivted crop for the totl soil profile (-9 cm) nd for ech soil lyer of 3 cm. The vlues in bold in Tble 45 hve high levels of nitrte (> 9 kg N/h) in utumn 212. However, since 211 the llowed mximum nitrte residue in the soil profile from -9 cm depends on the cultivted crop, soil type, nd focus or non-focus re. Therefore, the vlues in bold (> 9 kg NO 3 -N/h) re indictive. Since only the verge of prcels, which were no outlier in utumn 212 nd no outlier in spring 213, re shown, the vlues for utumn 212 in Tble 45 re not identicl s vlues shown in Tble

129 Tble 45: Averge nitrte-n (kg/h) in the soil profile in utumn 212 nd spring 213. The nitrte-n is given for the different combintions of soil texture, cultivted crop nd derogtion in 212. For ech combintion the totl mount of nitrte is given s well s for ech soil lyer (lyer 1: -3 cm, lyer 2: 3-6 cm nd lyer 3: 6-9 cm). The number of prcels is indicted by n. Soil Crop 212 n Autumn 212 Nitrte-N (kg/h) in spring cm -3cm 3-6cm 6-9cm -9cm Derogtion 75 Cly Beets Grss Mize Winter whet Lom Beets Grss Mize Winter whet Snd Beets Grss Mize Winter whet Sndy lom Beets Grss Mize Winter whet No derogtion 16 Cly Beets Grss Mize Winter whet Other Lom Beets Grss Mize Winter whet Other Snd Beets Grss Mize Winter whet Other Sndy lom Beets Grss Mize Winter whet Other

130 The reltion between nitrte in the soil profile from -9 cm in utumn 212 nd spring 213 is shown in sctterplot (Figure 83). A significnt correltion (p.5) exists. The regression model explined 1 % of the vrince. 7 Nitrte in the soil profile in utumn 212 nd spring 213 Y = *x, R² =.1, p <.5 Nitrte-N in spring 213 (kg/h) Nitrte-N in utumn 212 (kg/h) Figure 83: Sctterplot of the nitrte-n (kg/h) in the soil profile from -9 cm in utumn 212 versus the nitrte-n (kg/h) in the soil profile from -9 cm in spring All crops on ll soil textures In the first prt of the sttisticl nlysis, the totl mount of nitrte-n in spring 213 is compred for ll crops on ll soil textures between derogtion nd no derogtion prcels. In both derogtion nd no derogtion prcels, the nitrte mesurement shows lrge vrition (Figure 84). Since no derogtion crops (vegetbles,...) re present in this dtset, the compred groups re not homogeneous nd no sttisticl nlysis ws conducted between derogtion nd no derogtion prcels. 128

131 1.9 All crops on ll soil textures log(nitrte) Nitrte-N (kg/h) Derogtion J der No Nderogtion Men Men±SE Men±2*SD Figure 84: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels with ll crops on ll soil textures in spring 213. SE: stndrd error of the men. SD: stndrd devition. The verge mount of nitrte-n is 26 ± 14 kg/h on derogtion prcels nd 25 ± 11 kg/h on no derogtion prcels (Figure 85). The mount of nitrte is more or less eqully distributed over ll three soil lyers cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 85: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels with ll crops on ll soil textures in spring

132 6.1.2 Derogtion crops on ll soil textures In next step derogtion nd no derogtion prcels cultivted with only derogtion crops (grss, mize, beets, winter whet) re compred. The mesured nitrte vlues re highly vrible (Figure 86). 1.9 Derogtion crops on ll soil textures log(nitrte) Nitrte-N (kg/h) Derogtion J evnir No derogtion N Men Men±SE Men±2*SD Figure 86: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on ll soil textures in spring 213. SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 87: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels for derogtion crops on ll soil textures in spring 213. The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 13

133 No sttisticlly significnt difference ws found between nitrte-n mesured on derogtion (26 ± 14 kg N/h) nd no derogtion (25 ± 1 kg N/h) prcels (Figure 87, p =.98). The mount of nitrte is more or less eqully distributed over ll three soil lyers Derogtion crops on sndy soils In the next step, significnt differences between derogtion nd no derogtion prcels for the most importnt soil textures nd derogtion crops re explored. There is lrge vrition within one group (both on derogtion or no derogtion) (Figure 88). 1.9 Derogtion crops on sndy soils log(nitrte) Derogtion J No Nderogtion Men Men±SE Men±2*SD Figure 88: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on sndy soils in spring 213. SE: stndrd error of the men. SD: stndrd devition. The verge vlue of nitrte-n for derogtion crops on sndy soils is 24 ± 13 kg/h for derogtion prcels nd 27 ± 18 kg/h for no derogtion prcels. The mount of nitrte-n mesured in sndy soils on derogtion prcels from -9 cm does not differ significntly from the mount of nitrte-n mesured on no derogtion prcels (Figure 89, p =.66). 131

134 Nitrte-N (kg/h) Nitrte-N (kg/h) cm 3-6 cm 6-9 cm 1 Derogtion No derogtion Figure 89: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels for derogtion crops on sndy soils in spring 213. The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Grss nd mize on sndy soils So fr no significnt differences were found between derogtion nd no derogtion prcels for ll crops nd soil textures nd for derogtion crops on sndy soils. Since grss nd mize re mostly cultivted on sndy soils, these combintions re compred seprtely for grss nd mize by mens of one-wy ANOVA (p.5) on the log-trnsformed dt (Figure 9) ' ' -3 cm 3-6 cm 6-9 cm Derogtion Grss No derogtion Derogtion No derogtion Mïze Figure 9: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels with grss or mize on sndy soils in spring 213. The results for grss nd mize were nlysed seprtely. A one-wy ANOVA (p.5) ws conducted on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 132

135 For grss the nitrte-n ws 19 ± 8 kg/h on derogtion prcels nd 27 ± 24 kg/h on no derogtion prcels. For mize the nitrte-n ws 3 ± 16 kg/h on derogtion prcels nd 28 ± 15 kg/h on no derogtion prcels. There is no significnt difference between derogtion nd no derogtion prcels cultivted with grss (p =.81) or with mize (p =.7) Derogtion crops on sndy lom soils Next, derogtion nd no derogtion prcels cultivted with derogtion crops on sndy lom soils were investigted. On both derogtion nd no derogtion prcels on sndy lom soil, lrge vrition is observed (Figure 91). No significnt difference ws found between derogtion (34 ± 25 kg N/h) nd no derogtion prcels (3 ± 23 kg N/h) on sndy lom soils (Figure 92, p =.65) by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. 2. Derogtion crops on sndy lom soils log(nitrte) Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 91: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on sndy lom soils in spring 213. SE: stndrd error of the men. SD: stndrd devition. 133

136 Nitrte-N (kg/h) Nitrte-N (kg/h) cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 92: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels for derogtion crops on sndy lom soil in spring 213. The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Grss nd mize on sndy lom soils Figure 93 shows the verge vlues of nitrte-n in the totl soil profile nd the different soil lyers for grss nd mize on sndy lom soils ' ' -3 cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Derogtion No derogtion Grss Mïze Figure 93: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels with grss or mize on sndy lom soils in spring 213. The results for grss nd mize were nlysed seprtely. A one-wy ANOVA (p.5) ws conducted on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 134

137 For grss the verge nitrte-n ws 35 ± 31 kg/h on derogtion prcels nd 3 ± 28 kg /h on no derogtion prcels. For mize the verge nitrte level ws 31 ± 13 kg N/h on derogtion prcels nd 31 ± 22 kg N/h on no derogtion prcels (Figure 93). A sttisticl nlysis between derogtion nd no derogtion prcels ws conducted seprtely for grss nd mize by mens of one-wy ANOVA (p.5) of the log-trnsformed dt. There is no sttisticl significnt difference between derogtion nd no derogtion prcels cultivted with grss (p =.62) or with mize (p =.87) Nitrte in spring 213 in the deeper soil lyer For 3 prcels n dditionl soil smple ws tken from 9 to 12 cm (the deep soil smple ). In this soil lyer the mount of nitrte is mesured. No significnt correltion (p =.8) exists between the mount of nitrte present in the soil profile from -9 cm nd the nitrte present in the soil profile from 9-12 cm. The mount of nitrte in the soil lyer 9-12 cm is low. 3 Nitrte in the soil profile in spring 213 Y = *x, R² =.12, p = cm cm Figure 94: Sctterplot of the nitrte-n (kg/h) in the soil profile from -9 cm versus the nitrte-n (kg/h) in the soil profile from 9-12 cm in spring

138 The deep soil smples re tken on selection of prcels. Therefore it is not possible to crry out sttisticl nlysis for ll combintions of derogtion, soil texture nd cultivted crop. The comprison ws limited to grss nd mize on ll soil textures. The sttisticl nlysis ws conducted for grss nd mize seprtely. No significnt difference ws found between derogtion nd no derogtion prcels in the soil lyer from 9 to 12 cm for grss (p =.8) or mize (p =.23). There is lso no significnt difference between derogtion nd no derogtion prcels in the soil lyer from -12 cm for grss (p =.2 ) or mize (p =.35). The verge level of nitrte-n in the soil lyer -12 cm on prcels cultivted with grss under derogtion is 27 ± 25 kg/h nd 15 ± 2 kg/h without derogtion. The verge level of nitrte-n in the soil lyer - 12 cm on prcels cultivted with mize under derogtion is 29 ± 21 kg/h nd 4 ± 17 kg/h without derogtion. The deep soil lyer contined lmost no nitrte-n in spring 213. In utumn 212 this soil lyer contined in reltive terms more nitrte thn in utumn 211 nd bundnt rinfll in December 212 (Figure 247) resulted in n empty soil lyer 9-12 cm in spring 213. Figure 95: Averge nitrte-n (kg/h) in the 4 soil lyers on derogtion nd no derogtion prcels on ll soil textures cultivted with grss or mize, spring 213. The results for grss nd mize were nlysed seprtely. A one-wy ANOVA (p.5) ws conducted on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 136

139 6.12 Nitrte in utumn 213 Between October 1 st nd November 15 th, soil smples were tken in order to determine the mount of nitrte in the soil profile from to 3, 3 to 6 nd 6 to 9 cm. In the next prgrphs, box plots show the vrition of the groups (derogtion nd no derogtion). The dt were log-trnsformed in order to obtin normlity of the dtset. All dt re shown visully in br grphs, which show the distribution of nitrte in the soil profile (-3 cm, 3-6 cm, 6-9 cm). The results of homogeneous groups re nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. One prcel ws detected s sttisticl outlier. The log of the nitrte content in the soil profile - 9 cm on the prcel exceeded the verge plus 2 times the stndrd devition. It ws mize prcel without derogtion on sndy soil with nitrte residue of 261 kg NO 3 -N/h. No exubernt fertilistion ws pplied nd hrvest ws good. The verge nitrte in the soil profile for ech soil lyer nd for different combintions of crop, soil texture nd derogtion is shown in Tble 46. The vlues in bold re verge nitrte residues lrger thn 9 kg NO 3 -N/h. However, since 211 the llowed mximum nitrte residue in the soil profile from -9 cm depends on the cultivted crop, soil type, focus or non-focus re. Therefore, the vlues in bold in the tble (> 9 kg NO 3 -N/h) re indictive. Although winter whet is crop with low verge nitrte residue, high nitrte residues re mesured on prcels of the monitoring network cultivted with winter whet. On the derogtion prcels on snd nd sndy lom soil cultivted with winter whet, cover crops were sown but niml mnure ws pplied in August fter hrvest. On cly soil the three prcels with no derogtion crops were cultivted with pottoes. Nitrte residues of 162, 174 nd 189 kg N/h were mesured. Pottoes re often crop with higher nitrte residue. 137

140 Tble 46: Averge nitrte-n (kg/h) in the soil profile in utumn 213. The nitrte-n is given for the different combintions of soil texture, cultivted crop nd derogtion in 213. For ech combintion the totl mount of nitrte is given s well s for ech soil lyer (lyer 1 : -3 cm, lyer 2: 3-6 cm nd lyer 3: 6-9 cm). The number of prcels is indicted with n. Soil Crop 213 n Nitrte-N (kg/h) -3 cm 3-6 cm 6-9 cm -9 cm Derogtion 16 Cly Beets Grss Mize Winter whet Lom Beets Grss Mize Winter whet Snd Beets Grss Mize Winter whet Sndy lom Beets Grss Mize Winter whet No derogtion 99 Cly Beets Grss Mize Winter whet Other Lom Beets Grss Mize Winter whet Other Snd Beets Grss Mize Winter whet Other Sndy lom Beets Grss Mize Winter whet Other

141 All crops on ll soil textures For both derogtion nd no derogtion prcels, lrge vrition in mount of nitrte in the soil profile (-9 cm) is observed (Figure 96). On derogtion prcels the mount of nitrte-n rnged from 8 to 242 kg. For prcels without derogtion the rnge ws 6 to 261 kg N/h. 2,6 All crops on ll soil textures 2,4 2,2 2, log(nitrte) Nitrte-N (kg/h) 1,8 1,6 1,4 1,2 1,,8 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 96: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels in utumn 213, for ll crops on ll soil textures. SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 97: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 213 for ll crops on ll soil textures. 139

142 The verge nitrte-n in the soil profile (-9 cm) is 61 (± 47) kg N/h for derogtion prcels nd 69 (± 53) kg N/h for no derogtion prcels (Figure 97). The first two lyers contin the most nitrte-n while the lyer 6-9 contins less thn the lyers bove. This is the most pronounced for the no derogtion prcels. Since ll crops (vegetbles, pottoes,...) re included in this dtset, the groups of derogtion nd no derogtion prcels re no homogeneous groups. These groups cnnot be sttisticlly compred Derogtion crops on ll soil textures To conduct sttisticl nlysis the further comprisons re limited to prcels cultivted with derogtion crop (grss, mize, winter whet nd beets). There is lrge vrince in nitrte in the soil (-9 cm) on derogtion nd no derogtion prcels (Figure 98). The mount of nitrte-n on derogtion prcels (61 ± 47 kg N/h) ws not significntly different from the mount on no derogtion prcels (61 ± 46 kg N/h) (p =.9) (Figure 99). 2,6 Derogtion crops on ll soil types 2,4 2,2 2, log(nitrte) 1,8 1,6 1,4 1,2 1,,8 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 98: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on ll soil textures in utumn 213. SE: stndrd error of the men. SD: stndrd devition. 14

143 Nitrte-N (kg/h) cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 99: Averge nitrte-n (kg N/h) on derogtion nd no derogtion prcels for derogtion crops on ll soil textures in utumn 213. These results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. The nitrte residue will be sttisticlly compred between derogtion nd no derogtion prcels for specific soil textures. Since sndy nd sndy lom soils re the soil textures on which derogtion is mostly requested, the effect of derogtion on the nitrte residue will be discussed in more detil in the following prgrphs for these soil textures. The dt for the other soil textures re listed in Tble Derogtion crops on sndy soils Like shown for ll soils, on sndy soils there is lrge vrince for both groups of prcels (Figure 1). Derogtion nd no derogtion prcels on sndy soils cultivted with derogtion crops did not differ significntly (p =.8). On the derogtion prcels the verge mount of nitrte-n ws 62 (± 48) kg N/h nd on no derogtion prcels 68 (± 59) kg N/h (Figure 11). 141

144 Nitrte-N (kg/h) 2,8 Derogtion crops on sndy soils 2,6 2,4 2,2 2, log(nitrte) 1,8 1,6 1,4 1,2 1,,8,6,4 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 1: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on sndy soils in utumn 213. SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 11: Averge nitrte-n (kg N/h) on derogtion nd no derogtion prcels for derogtion crops on sndy soils in utumn 213. These results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Grss nd mize on sndy soils The derogtion crops grown on sndy soils re mostly grss nd mize. Comprison of derogtion nd no derogtion prcels on sndy soil with grss (p =.37) or mize (p =.65) showed no sttisticl differences. Derogtion prcels with grss on sndy soils hve nitrte 142

145 Nitrte-N (kg/h) residue of 52 ± 45 kg N/h nd the no derogtion prcels with grss 54 ± 58 kg N/h. For mize prcels the derogtion prcels hd nitrte residue of 71 ± 46 kg N/h in the soil profile nd the no derogtion prcels 74 ± 41 kg N/h. Although there is no sttisticlly significnt difference, the no derogtion prcels grown with mize tend to hve higher mount of nitrte- N in the soil profile in utumn 213 on sndy soils ' ' cm cm cm 1 Derogtion No derogtion Grss Derogtion No derogtion Mïze Figure 12: Averge nitrte-n (kg N/h) on derogtion nd no derogtion prcels cultivted with grss or mize on sndy soils in utumn 213. The results for grss nd mize were nlysed seprtely. These results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Derogtion crops on sndy lom soils The second soil type on which derogtion is frequently requested, is sndy lom. The vrince in nitrte residue is for both derogtion nd no derogtion prcels lrge (Figure 13). On the no derogtion prcels with derogtion crops on sndy loms soils the vrince ws smller thn on the derogtion prcels, just like in utumn 212. The derogtion prcels on sndy lom showed n verge nitrte residue of 56 ± 51 kg N/h nd the no derogtion prcels lmost the sme (53 ± 32 kg N/h) (Figure 14). 143

146 Nitrte-N (kg/h) 2,6 Derogtion crops on sndy lom soils 2,4 2,2 2, log(nitrte) 1,8 1,6 1,4 1,2 1,,8,6 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 13: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on sndy lom soils in utumn 213. SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 14: Averge nitrte-n (kg N/h) on derogtion nd no derogtion prcels for derogtion crops on sndy lom soils in utumn 213. These results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Grss nd mize on sndy lom soils Grss nd mize re the most commonly grown derogtion crops on sndy loms soils. For these crops seprte sttisticl nlysis is conducted. Nor for grss (p =.95) nor for mize (p =.56) there ws sttisticl significnt difference between derogtion nd no derogtion prcels (Figure 144

147 Nitrte-N (kg/h) 15). The verge mount of nitrte-n on derogtion prcels with grss is 43 ± 45 kg N/h on sndy lom soils. On the no derogtion prcels with grss this ws 34 ± 23 kg N/h. On the mize prcels with nd without derogtion the verge nitrte residue ws 65 ± 56 kg N/h nd 66 ± 33 kg N/h ' ' cm 3-6 cm cm 1 Derogtion No derogtion Grss Derogtion No derogtion Mïze Figure 15: Averge nitrte-n (kg N/h) on derogtion nd no derogtion prcels cultivted with grss or mize on sndy lom soils in utumn 213. The results for grss nd mize were nlysed seprtely. These results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Nitrte in utumn 213, prcels which were continuously under derogtion/no derogtion during In order to verify the long-term impct of derogtion on the nitrte residue, only the prcels which were continuously under derogtion/no derogtion during were retined for sttisticl nlysis. In the next prgrphs, box plots show the vrition of the groups (derogtion nd no derogtion). The dt were log-trnsformed in order to obtin normlity of the dtset. All dt re shown visully in br grphs, which show the distribution of nitrte in the soil profile (-3 cm, 3-6 cm, 6-9 cm). 145

148 On both derogtion nd no derogtion prcels, lrge vrition in nitrte residue in utumn 213 is noticed. The verge nitrte-n on derogtion prcels is 6 ± 48 kg/h nd on no derogtion prcels 61 ± 49 kg/h. Since no limittion to derogtion crops, no sttisticl nlysis is crried out. 2,6 All crops on ll soil textures 2,4 2,2 2, log(nitrte) Nitrte-N (kg/h) 1,8 1,6 1,4 1,2 1,,8 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 16: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels on ll soil textures in utumn 213, including only prcels which were continuously under derogtion/no derogtion during ; SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 17: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 213 on ll soil textures, including only prcels which were continuously under derogtion/no derogtion during

149 Since snd nd sndy lom re the soil textures on which derogtion is most frequently requested, the long-term impct of derogtion/no derogtion is shown seprtely for these soil textures. Figure 18 shows lrge vrition in nitrte residue for long-term derogtion nd no derogtion prcels on sndy soils. The verge nitrte residue on derogtion prcels is 63 ± 43 kg/h nd 64 ± 56 kg/h on no derogtion prcels (Figure 19). 2,6 All crops on sndy soils 2,4 2,2 2, log(nitrte) Nitrte-N (kg/h) 1,8 1,6 1,4 1,2 1,,8,6 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 18: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels on sndy soils in utumn 213, including only prcels which were continuously under derogtion/no derogtion during ; SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 19: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 213 on sndy soils, including only prcels which were continuously under derogtion/no derogtion during

150 The vrition in nitrte residue for long-term derogtion nd no derogtion prcels on sndy lom soils is shown in Figure 11. The vrition on the prcels without derogtion is obviously smller thn on the derogtion prcels. The verge nitrte residue on derogtion prcels is 54 ± 47 kg/h nd 52 ± 33 kg/h on no derogtion prcels (Figure 111). 2,6 All crops on sndy lom soils 2,4 2,2 2, log(nitrte) Nitrte-N (kg/h) 1,8 1,6 1,4 1,2 1,,8,6 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 11: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels on sndy lom soils in utumn 213, including only prcels which were continuously under derogtion/no derogtion during ; SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 111: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 213 on sndy lom soils, including only prcels which were continuously under derogtion/no derogtion during

151 On the prcels continuously grown with grss in the period the vrition of the nitrte Nitrte-N (kg/h) residues on both types of prcels ws high nd no sttisticl difference between derogtion nd no derogtion prcels is detected (p =.44) (Figure 112). 2, Long term grss prcels on ll soils 1,8 1,6 1,4 log(nitrte) 1,2 1,,8,6,4,2, Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 112: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels on ll soils in utumn 213, including only prcels which were continuously under derogtion/no derogtion during nd grown with grss; SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 113: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 213 on ll soils, including only prcels which were continuously under derogtion/no derogtion during nd grown with grss. The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 149

152 Nitrte-N (kg/h) On the prcels continuously under derogtion in the period nd continuously grown with grss the nitrte residue ws 56 ± 42 kg N/h in utumn 213 nd 41 ± 42 kg N/h on no derogtion prcels (Figure 113). Since not enough long-term mize prcels were vilble, no sttisticl nlysis is crried out. But Figure 114 shows tht the verge nitrte residues were close. On prcels continuously under derogtion in the period nd grown with mize every yer, the nitrte residue ws 55 ± 25 kg N/h in utumn 213. On prcels continuously without derogtion in the period nd grown with mize every yer, the nitrte residue ws 57 ± 32 kg N/h Derogtion No derogtion -3 cm 3-6 cm 6-9 cm Figure 114: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 213 on ll soils, including only prcels which were continuously under derogtion/no derogtion during nd grown with mize Nitrte in utumn 213 in the deeper soil lyer In utumn 213 for 36 prcels n dditionl soil smple ws tken from 9 to 12 cm (the deep soil smple ). In this soil lyer the mount of nitrte is mesured. Dt re considered sttisticl outliers when exceeding the verge plus 2 times the stndrd devition. One outlier is removed. A derogtion prcel on sndy soil cultivted with grss, with 128 kg N/h in the soil lyer On this prcel the soil lyers bove contined 144 kg N/h (27 kg N/h in the soil lyer - 3 cm, 48 kg N/h in the soil lyer 3-6 cm nd 69 kg N/h in the soil lyer 6-9 cm). After mowing, the prcel ws grzed until November. In utumn 213 significnt correltion (p =.) exists between the mount of nitrte in the soil profile from -9 cm nd the mount of nitrte in the soil lyer from 9-12 cm (Figure 115). 15

153 1 Nitrte in the soil profile in utumn 213 Y= *x; 9-12cm = 3,8873+,3922*x R²=.51; p= cm cm Figure 115: Sctterplot of the nitrte-n (kg/h) in the soil profile from -9 cm versus the nitrte-n (kg/h) in the soil profile from 9-12 cm in utumn 213. Since the deep soil smples re tken on selection of prcels, it is not possible to crry out sttisticl nlysis for ll combintions of derogtion, soil texture nd cultivted crop. A comprison is mde of derogtion nd no derogtion prcels with grss or mize on ll soil textures. 2, Grss ll soils 2,4 Mize ll soils 1,8 2,2 log(nitrte) 9-12 cm 1,6 1,4 1,2 1,,8,6,4 log(nitrte) 9-12 cm 2, 1,8 1,6 1,4 1,2 1,,8,6,4,2, Derogtion J No derogtion N Men Men±SE Men±2*SD,2, Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 116: Box plot of log(nitrte-n, 9-12 cm) for derogtion nd no derogtion prcels in utumn 213, for grss (left) nd mize (right) on ll soil textures. SE: stndrd error of the men. SD: stndrd devition. 151

154 Nitrte-N (kg/h) The verge nitrte-n content in the soil lyer 9-12 cm on derogtion prcels with grss in utumn 213 is 18 ± 11 kg/h nd 13 ± 11 kg/h on no derogtion prcels. For mize prcels the nitrte content in the soil lyer 9-12 cm in utumn 213 is 25 ± 18 kg/h on derogtion prcels nd 34 ± 37 kg/h on no derogtion prcels. The verge level of nitrte-n in the soil profile till 12 cm on prcels cultivted with grss under derogtion is 51 ± 35 kg/h nd 69 ± 67 kg/h under no derogtion. The verge level of nitrte-n in the soil profile till 12 cm on prcels cultivted with mize under derogtion is 77 ± 62 kg/h nd 93 ± 8 kg/h under no derogtion (Figure 118). 2,6 Grss ll soils 2,8 Mize ll soils 2,4 2,6 2,2 2,4 log(nitrte) -12cm 2, 1,8 1,6 1,4 log(nitrte) -12 cm 2,2 2, 1,8 1,6 1,4 1,2 1,2 1,,8 Derogtion J No derogtion N Men Men±SE Men±2*SD 1,,8 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 117: Box plot of log(nitrte-n, -12 cm) for derogtion nd no derogtion prcels in utumn 213, for grss (left) nd mize (right) on ll soil textures. SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm cm 1 Derogtion No derogtion Grss Derogtion No derogtion Mïze Figure 118: Averge nitrte-n (kg/h) in the 4 soil lyers on derogtion nd no derogtion prcels on ll soil textures cultivted with grss or mize, utumn

155 In verge 33 to 36 % of the nitrte-n in the soil profile -12 cm is situted in the soil lyer 9-12 cm in utumn 213 on derogtion prcels cultivted with grss nd derogtion nd no derogtion prcels cultivted with mize. On the no derogtion prcels cultivted with grss, only 19 % of the nitrte-n content ws situted in the deepest soil lyer Nitrte in spring 214 On the prcels of the monitoring network nitrte smple hs been tken in spring 214. This nitrte smple consists of three soil lyers (-3 cm, 3-6 cm nd 6-9 cm) nd provides informtion on the mount of nitrte in the soil profile fter winter nd the mount vilble to the cultivted crop for the next growing seson. Every frmer receives nitrte fertilistion dvice, bsed on the N-INDEX expert system (Geypens et l., 1994). The verge level of nitrte mesured in the soil smples in utumn 213 nd spring 214 is shown in Tble 47. The mount of nitrte is given for the combintions of derogtion, soil texture nd cultivted crop for the totl soil profile (-9 cm) nd for ech soil lyer of 3 cm in spring. The vlues in bold in Tble 47 hve high levels of nitrte (> 9 kg N/h) in utumn 213. However, since 211 the llowed mximum nitrte residue in the soil profile from -9 cm depends on the cultivted crop, soil type, focus or non-focus re. Therefore, the vlues in bold re indictive. Not ll prcels re covered by the shown verge vlues, since some prcels were lredy fertilised in spring 214 while other prcels were detected s sttisticl outlier in utumn 213 or spring 214. Therefore vlues in Tble 47 for utumn 213 re not identicl to those shown in Tble 46. In spring 214, two prcels were detected s sttisticl outlier. One prcel ws lso detected s sttisticl outlier in utumn 213. It ws cultivted with mize in 213 without derogtion on sndy soil with nitrte residue of 261 kg NO 3 -N/h. No exubernt fertilistion ws pplied nd hrvest hd been good. The mount of nitrte-n t Februry 1 st ws 167 kg N/h. On the second prcel detected s outlier in spring 214, the mount of nitrte-n ws 17 kg N/h t Jnury 28 th. No fertilistion hd lredy been pplied t tht moment but the prcel ws grzed in utumn

156 Tble 47: Averge nitrte-n (kg/h) in the soil profile in utumn 213 nd spring 214. The nitrte-n is given for the different combintions of soil texture, cultivted crop nd derogtion in 213. For ech combintion the totl mount of nitrte is given s well s for ech soil lyer (lyer 1: -3 cm, lyer 2: 3-6 cm nd lyer 3: 6-9 cm). The number of prcels is indicted by n. Soil Crop 213 n Autumn 213 Nitrte-N (kg/h) in spring cm -3cm 3-6cm 6-9cm -9cm Derogtion 86 Cly Beets Grss Mize Winter whet Lom Beets Grss Mize Winter whet Snd Beets Grss Mize Winter whet Sndy lom Beets Grss Mize Winter whet No derogtion 85 Cly Beets Grss Mize Winter whet Other Lom Beets Grss Mize Winter whet Other Snd Beets Grss Mize Winter whet Other Sndy lom Beets Grss Mize Winter whet Other

157 The reltion between nitrte in the soil profile from -9 cm in utumn 213 nd spring 214 is shown in sctterplot (Figure 119). A significnt correltion (p.5) exists. Three percent of the vrince is explined by the model. 9 Nitrte in the soil profile in utumn 213 nd spring 214 Y = *x, R² =.3, p<.5 8 Nitrte-N in spring 214 (kg/h) Nitrte-N in utumn 213 (kg/h) Figure 119: Sctterplot of the nitrte-n (kg/h) in the soil profile from -9 cm in utumn 213 versus the nitrte-n (kg/h) in the soil profile from -9 cm in spring All crops on ll soil textures In the first prt of the sttisticl nlysis, the totl mount of nitrte in spring 214 between derogtion nd no derogtion prcels is compred for ll crops on ll soil textures. On both derogtion nd no derogtion prcels, the nitrte mesurements show lrge vrition (Figure 12). Since no derogtion crops (vegetbles,...) re present in this dtset, the compred groups re not homogeneous nd no sttisticl nlysis ws conducted between derogtion nd no derogtion prcels. 155

158 2,2 All crops on ll soil textures 2, 1,8 1,6 log(nitrte) Nitrte-N (kg/h) 1,4 1,2 1,,8,6,4 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 12: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels with ll crops on ll soil textures in spring 214. SE: stndrd error of the men. SD: stndrd devition. The verge mount of nitrte-n is 23 ± 16 kg/h for derogtion prcels nd 26 ± 18 kg/h for no derogtion prcels (Figure 121). The mount of nitrte is more or less eqully distributed over ll three soil lyers cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 121: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels with ll crops on ll soil textures in spring

159 Derogtion crops on ll soil textures In next step derogtion nd no derogtion prcels cultivted with only derogtion crops (grss, mize, beets, winter whet) re compred. The mesured nitrte vlues re highly vrible (Figure 122). 2,2 Derogtion crops on ll soil textures 2, 1,8 1,6 log(nitrte) 1,4 1,2 1,,8,6,4 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 122: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on ll soil textures in spring 214. SE: stndrd error of the men. SD: stndrd devition. No sttisticlly significnt difference ws found between nitrte-n mesured on derogtion (23 ± 16 kg N/h) nd no derogtion (27 ± 18 kg N/h) prcels (Figure 123, p =.24). The mount of nitrte is more or less eqully distributed over ll three soil lyers. 157

160 Nitrte-N (kg/h) cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 123: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels for derogtion crops on ll soil textures in spring 214. The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Derogtion crops on sndy soils In the next step, significnt differences between derogtion nd no derogtion prcels for the most importnt soil textures nd derogtion crops re explored. 2,2 Derogtion crops on sndy soils 2, 1,8 1,6 log(nitrte) 1,4 1,2 1,,8,6,4 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 124: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on sndy soils in spring 214. SE: stndrd error of the men. SD: stndrd devition. 158

161 Nitrte-N (kg/h) The verge vlue of nitrte-n for derogtion crops on sndy soils is 21 ± 15 kg/h for derogtion prcels nd 27 ± 19 kg/h for no derogtion prcels. There is lrge vrition within ech group (Figure 124). The nitrte-n mesured on sndy soils on derogtion prcels from -9 cm does not differ significntly from the nitrte mesured on no derogtion prcels (Figure 125, p =.15) cm 3-6 cm 6-9 cm 1 Derogtion No derogtion Figure 125: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels for derogtion crops on sndy soils in spring 214. The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Grss nd mize on sndy soils So fr no significnt differences were found between derogtion nd no derogtion for derogtion crops on sndy soils. Since grss nd mize re mostly cultivted on sndy soils, these combintions re compred seprtely for grss nd mize by mens of one-wy ANOVA (p.5) on the log-trnsformed dt (Figure 126). For grss the nitrte-n ws 17 ± 11 kg /h in derogtion prcels nd 22 ± 14 kg/h in no derogtion prcels. For mize the nitrte-n ws 28 ± 18 kg/h on derogtion prcels nd 36 ± 22 kg/h on no derogtion prcels. There is no significnt difference between derogtion nd no derogtion prcels cultivted with grss (p =.22) or with mize (p =.24). 159

162 Nitrte-N (kg/h) ' ' -3 cm 3-6 cm 6-9 cm 1 Derogtion No derogtion Grss Derogtion No derogtion Mïze Figure 126: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels with grss or mize on sndy soils in spring 214. The results for grss nd mize were nlysed seprtely. A one-wy ANOVA (p.5) ws conducted on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Derogtion crops on sndy lom soils Next, derogtion nd no derogtion prcels cultivted with derogtion crops on sndy lom soils were compred. 2,2 Derogtion crops on sndy lom soils 2, 1,8 1,6 log(nitrte) 1,4 1,2 1,,8,6,4 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 127: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on sndy lom soils in spring 214. SE: stndrd error of the men. SD: stndrd devition. 16

163 Nitrte-N (kg/h) On both derogtion nd no derogtion prcels on sndy lom soil, lrge vrition is observed in the mount of nitrte-n (Figure 127). No significnt difference ws found between derogtion (24 ± 18 kg N/h) nd no derogtion prcels (25 ± 17 kg N/h) on sndy lom soils (Figure 128, p =.57) by mens of one-wy ANOVA (p.5) on the log-trnsformed dt cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 128: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels for derogtion crops on sndy lom soil in spring 214. The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Grss nd mize on sndy lom soils Figure 129 shows the verge vlues of nitrte-n in the totl soil profile nd the different soil lyers for grss nd mize on sndy lom soils. For grss the verge nitrte-n is 24 ± 22 kg/h on derogtion prcels nd 18 ± 6 kg /h on no derogtion prcels. For mize the verge nitrte level ws 25 ± 14 kg N/h on derogtion prcels nd 33 ± 2 kg N/h on no derogtion prcels (Figure 129). A sttisticl nlysis between derogtion nd no derogtion prcels ws conducted seprtely for grss nd mize by mens of one-wy ANOVA (p.5) of the log-trnsformed dt. There is no significnt difference between derogtion nd no derogtion prcels cultivted with grss (p=.91) or with mize (p=.31). 161

164 Nitrte-N (kg/h) cm ' ' 3-6 cm 6-9 cm 1 Derogtion No derogtion Grss Derogtion No derogtion Mïze Figure 129: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels with grss or mize on sndy lom soils in spring 214. The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Nitrte in spring 214, prcels which were continuously under derogtion/no derogtion during In order to verify the long-term impct of derogtion on the nitrte in the soil in spring 214, only the prcels which were continuously under derogtion/no derogtion during were compred. In this prgrph box plots show the vrition of the groups (derogtion nd no derogtion). The dt were log-trnsformed in order to obtin normlity of the dtset. All dt re shown visully in br grphs, which show the distribution of nitrte in the soil profile (-3 cm, 3-6 cm, 6-9 cm). On both derogtion nd no derogtion prcels the vrition in mount of nitrte-n in the soil profile -9 cm in spring 214 is rther lrge s shown in Figure 13. In spring 214 the verge nitrte-n on derogtion prcels is 23 ± 15 kg/h nd 26 ± 18 kg/h on no derogtion prcels (Figure 131). The nitrte-n is on both types of prcels, derogtion or no derogtion, eqully distributed in the lyers -3 cm, 3-6 cm nd 6-9 cm. 162

165 2,2 All crops on ll soil textures 2, 1,8 1,6 log(nitrte) Nitrte-N (kg/h) 1,4 1,2 1,,8,6,4 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 13: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels on ll soil textures in spring 214, including only prcels which were continuously under derogtion/no derogtion during ; SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 131: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in spring 214 on ll soil textures, including only prcels which were continuously under derogtion/no derogtion during For the most importnt soil textures for derogtion, snd nd sndy lom, the comprison between derogtion nd no derogtion prcels is mde seprtely. Since on the no derogtion prcels lso no derogtion crops re grown no sttisticl nlysis is crried out. 163

166 On sndy soils the verge nitrte-n in the soil profile of long-term derogtion prcels is 21 ± 15 kg/h in spring 214 nd 24 ± 17 kg/h on no derogtion prcels (Figure 133). 2, All crops on sndy soils 1,8 1,6 1,4 log(nitrte) Nitrte-N (kg/h) 1,2 1,,8,6,4 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 132: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels on sndy soils in spring 214, including only prcels which were continuously under derogtion/no derogtion during ; SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 133: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in spring 214 on sndy soils, including only prcels which were continuously under derogtion/no derogtion during

167 In spring 214 the vrition in nitrte-n on no derogtion prcels ws lmost the sme s the vrition on derogtion prcels on sndy lom soils (Figure 134). The verge nitrte-n is 24 ± 11 kg/h on derogtion prcels nd 27 ± 18 kg/h on no derogtion prcels (Figure 135). 2, All crops on sndy loms soils 1,8 1,6 log(nitrte) Nitrte-N (kg/h) 1,4 1,2 1,,8,6 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 134: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels on sndy lom soils in spring 214, including only prcels which were continuously under derogtion/no derogtion during ; SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 135: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in spring 214 on sndy lom soils, including only prcels which were continuously under derogtion/no derogtion during

168 On the prcels continuously under derogtion in the period nd continuously grown with grss the mount of nitrte-n ws 24 ± 21 kg N/h in spring 214 nd 27 ± 29 kg N/h on no derogtion prcels (Figure 137). Figure 136 shows tht the vrition in mount of nitrte-n on both types of prcels ws high nd no sttisticl difference between derogtion nd no derogtion prcels is detected (p =.77). 1 Long term grss prcels on ll soils 8 6 log(nitrte) Nitrte-N (kg/h) Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 136: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels on ll soils in spring 214, including only prcels which were continuously under derogtion/no derogtion during nd grown with grss; SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 137: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in spring 214 on ll soils, including only prcels which were continuously under derogtion/no derogtion during nd grown with grss. The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 166

169 Nitrte-N (kg/h) On the prcels continuously under derogtion in the period nd grown every yer with mize the mount of nitrte-n ws 32 ± 8 kg N/h in spring 214 nd 37 ± 22 kg N/h on no derogtion prcels (Figure 138) Derogtion No derogtion -3 cm 3-6 cm 6-9 cm Figure 138: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in spring 214 on ll soils, including only prcels which were continuously under derogtion/no derogtion during nd grown with mize Nitrte in spring 214 in the deeper soil lyer For selection of prcels n dditionl soil smple ws tken from 9 to 12 cm (the deep soil smple ). In this soil lyer the mount of nitrte is mesured. No sttisticl outliers were detected in spring 214. No significnt correltion (p =.12) is found between the mount of nitrte-n present in the soil profile from -9 cm nd the mount of nitrte-n present in the soil profile from 9-12 cm (Figure 139). The deep soil smples re tken on selection of prcels. Therefore it is not possible to crry out sttisticl nlysis for ll combintions of derogtion, soil texture nd cultivted crop. The comprison ws limited to grss nd mize on ll soil textures (Figure 14 nd Figure 141). The verge level of nitrte-n on prcels cultivted with grss for the soil lyer 9-12 cm under derogtion is 21 ± 23 kg/h nd under no derogtion 22 ± 18 kg/h. The verge level of nitrte-n on prcels cultivted with mize for the soil lyer 9-12 cm under derogtion is 15 ± 9 kg/h nd 34 ± 3 kg/h under no derogtion. 167

170 9 Nitrte in the soil profile in spring 214 Y= 13,2628+,4613*x, R²=,96, p=, cm cm Figure 139: Sctterplot of the nitrte-n (kg/h) in the soil profile from -9 cm versus the nitrte-n (kg/h) in the soil profile from 9-12 cm in spring ,4 Grss-ll soils 2,4 Mize-ll soils 2,2 2, 1,8 2,2 2, 1,6 1,8 log(nitrte) ,4 1,2 1,,8,6 log(nitrte) ,6 1,4 1,2 1,,4,8,2, -,2 -,4 Derogtion J No Nderogtion Men Men±SE Men±2*SD,6,4,2 Derogtion J No Nderogtion Men Men±SE Men±2*SD Figure 14: Box plot of log(nitrte-n, 9-12 cm) for derogtion nd no derogtion prcels in spring 214, for grss (left) nd mize (right) on ll soil textures. SE: stndrd error of the men. SD: stndrd devition. 168

171 Nitrte-N (kg/h) 2,6 Grss-ll soils 2,4 Mize-ll soils 2,4 2,2 2,2 2, 2, log(nitrte) -12 1,8 1,6 1,4 log (nitrte) -12 1,8 1,6 1,4 1,2 1, 1,2,8,6 Derogtion J No derogtion N Men Men±SE Men±2*SD 1,,8 Derogtion J No Nderogtion Men Men±SE Men±2*SD Figure 141: Box plot of log(nitrte-n, -12 cm) for derogtion nd no derogtion prcels in spring 214, for grss (left) nd mize (right) on ll soil textures. SE: stndrd error of the men. SD: stndrd devition. The soil lyer 9-12 cm contined the lrgest mount of nitrte-n (Figure 142). On derogtion prcels cultivted with grss 51 % of the nitrte-n in the lyer -12 cm ws situted in the soil lyer 9-12 cm. On no derogtion prcels with grss or mize the soil lyer 9-12 cm contined 44 % nd 54 % of the nitrte-n in the soil lyer -12 cm. On no derogtion prcels with grss the frction of nitrte-n in the soils lyer 9-12 cm ws limited to 34 % cm 3-6 cm 6-9 cm 9-12 cm 1 Derogtion No derogtion Grss Derogtion No derogtion Mïze Figure 142: Averge nitrte-n (kg/h) in the 4 soil lyers on derogtion nd no derogtion prcels on ll soil textures cultivted with grss or mize, spring

172 The verge level of nitrte-n in the soil lyer -12 cm on prcels cultivted with grss is 41 ± 23 kg/h under derogtion nd 49 ± 32 kg/h without derogtion. The verge level of nitrte-n in the soil lyer -12 cm on prcels cultivted with mize under derogtion is 45 ± 28 kg/h nd 63 ± 5 kg/h without derogtion Nitrte in utumn 214 Between October 1 st nd November 15 th, soil smples were tken in order to determine the mount of nitrte in the soil profile from to 3, 3 to 6 nd 6 to 9 cm. In the next prgrphs, box plots show the vrition of the groups (derogtion nd no derogtion). The dt were log-trnsformed in order to obtin normlity of the dtset. All dt re shown visully in br grphs, which show the distribution of nitrte in the soil profile (-3 cm, 3-6 cm, 6-9 cm). The results of homogeneous groups re nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. One prcel ws detected s sttisticl outlier. The logrithm of the nitrte content in the soil profile -9 cm on the prcel exceeded the verge plus 2 times the stndrd devition. It ws mize prcel on sndy soil with nitrte residue of 381 kg NO 3 -N/h. The sod of grss (sown in 27) ws terminted in utumn 213 by herbicide tretment, nd converted into mize in 214. The verge nitrte in the soil profile for ech soil lyer nd for different combintions of crop, soil texture nd derogtion is shown in Tble 48. The vlues in bold re verge nitrte residues lrger thn 9 kg NO 3 -N/h. However, since 211 the llowed mximum nitrte residue in the soil profile from -9 cm depends on the cultivted crop, soil type, nd focus or non-focus re. Therefore, the vlues in bold in the tble (> 9 kg NO 3 -N/h) re indictive. The highest verge nitrte residues were mesured on prcels cultivted with other crops. The other crops on cly nd lom soil were pottoes, fter which higher nitrte residues re mesured. On sndy lom soils other crops comprised in 214 besides pottoes lso vegetbles like leek, culiflower, spinch nd bens. On sndy lom prcels cultivted with pottoes the nitrte residue rnged between 41 nd 18 kg N/h. The nitrte residue on these prcels ws mostly round 9 kg N/h. The nitrte residue on the prcels on sndy lom soil cultivted with vegetbles rnged between 169 nd 256 kg N/h. On cly soil the nitrte residue of grss prcels without derogtion rnged between 24 nd 227 kg N/h. The prcels with nitrte residue of 227 kg N/h ws grzed until utumn

173 Tble 48: Averge nitrte-n (kg/h) in the soil profile in utumn 214. The nitrte-n is given for the different combintions of soil texture, cultivted crop nd derogtion in 214. For ech combintion the totl mount of nitrte is given s well s for ech soil lyer (lyer 1 : -3 cm, lyer 2: 3-6 cm nd lyer 3: 6-9 cm). The number of prcels is indicted with n. Soil Crop 214 n Nitrte-N (kg/h) in utumn 214-3cm 3-6cm 6-9cm -9cm Derogtion 8 Cly Beets Grss Mize Winter whet Lom Beets Grss Mize Winter whet Snd Beets Grss Mize Winter whet Sndy lom Beets Grss Mize Winter whet No derogtion 135 Cly Beets Grss Mize Winter whet Other Lom Beets Grss Mize Winter whet Other Snd Beets Grss Mize Winter whet Other Sndy lom Beets Grss Mize Winter whet Other

174 All Crops on ll soil textures Like every yer in utumn for both derogtion nd no derogtion prcels, lrge vrition in mount of nitrte-n in the soil profile (-9 cm) is observed in utumn 214 (Figure 143). On derogtion prcels the mount of nitrte-n rnged from 11 to 215 kg/h. On no derogtion prcels the mount of nitrte-n in the soil profile (-9 cm) rnged from 8 to 256 kg/h. 2,6 All crops on ll soil textures 2,4 2,2 2, log(nitrte) 1,8 1,6 1,4 1,2 1, Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 143: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels in utumn 214, for ll crops on ll soil textures. SE: stndrd error of the men. SD: stndrd devition The verge nitrte-n in the soil profile (-9 cm) is 62 (± 41) kg N/h for derogtion prcels nd 73 (± 55) kg N/h for no derogtion prcels (Figure 144). In the upper lyer of -3 cm pproximtely 42 % of the mount of nitrte-n in the soil profile until 9 cm is found. In the lyers 3-6 cm nd 6-9 cm bout 33 % nd 25 % is mesured. Since ll crops (vegetbles, pottoes,...) re included in this dtset, the groups of derogtion nd no derogtion prcels re no homogeneous groups. These groups cnnot be sttisticlly compred. Further comprisons re limited to prcels cultivted with derogtion crops (grss, mize, winter whet nd beets) to mke sttisticl nlysis possible. 172

175 Nitrte-N (kg/h) cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 144: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 214 for ll crops on ll soil textures Derogtion crops on ll soil textures Also for derogtion crops there s lrge vrince in nitrte-n in the soil profile (-9 cm) on derogtion nd no derogtion prcels (Figure 145). 2,6 Derogtion crops on ll soil textures 2,4 2,2 2, log(nitrte) 1,8 1,6 1,4 1,2 1,,8 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 145: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on ll soil textures in utumn 214. SE: stndrd error of the men. SD: stndrd devition. 173

176 Nitrte-N (kg/h) cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 146: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels for derogtion crops on ll soil textures in utumn 214. These results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. The mount of nitrte-n on derogtion prcels (62 ± 41 kg N/h) ws not significntly different from the mount of nitrte-n on no derogtion prcels (67 ± 49 kg N/h) (p =.91) (Figure 146). In further nlysis the nitrte residue on derogtion nd no derogtion prcels will be sttisticlly compred for specific soil textures. Since sndy nd sndy lom soils re the soils on which derogtion is mostly requested, the effect of derogtion on the nitrte residue will be discussed in more detil in the following prgrphs for these soil textures. The dt for the other soil textures re listed in Tble Derogtion crops on sndy soils On both derogtion nd no derogtion prcels on sndy soils the vrince in nitrte-n in the soil profile (-9 cm) is lrge (Figure 147). On sndy soils the mount of nitrte-n in the soil profile on derogtion prcels grown with derogtion crops rnged from 11 to 215 kg N/h. On no derogtion prcels grown with derogtion crops on sndy soils the mount of nitrte-n ws situted between 8 nd 226 kg N/h. The nitrte-n residue on these derogtion nd no derogtion prcels did not differ significntly (p =.8). 174

177 The verge nitrte residue on derogtion nd no derogtion prcels with derogtion crops on sndy soils ws respectively 64 (± 43) kg N/h nd 66 (± 46) kg N/h (Figure 148). Nitrte-N (kg/h) 2,4 Derogtion crops on sndy soils 2,2 2, log(nitrte) 1,8 1,6 1,4 1,2 1, Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 147: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on sndy soils in utumn 214. SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 148: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels for derogtion crops on sndy soils in utumn 214. These results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 175

178 Nitrte-N (kg/h) Grss nd mize on sndy soils The most frequently grown derogtion crops on sndy soils re grss nd mize. Comprison of derogtion nd no derogtion prcels on sndy soil with grss (p =.31) or mize (p =.52) showed no sttisticl differences. Derogtion prcels with grss on sndy soils hve nitrte residue of 6 ± 42 kg N/h nd the prcels without derogtion cultivted with grss 54 ± 45 kg N/h. For mize prcels the derogtion prcels hd n mount of 7 ± 48 kg NO 3 -N/h in the soil profile nd the no derogtion prcels 75 ± 45 kg NO 3 -N/h ' ' -3 cm cm cm 1 Derogtion No derogtion Grss Derogtion No derogtion Mïze Figure 149: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels cultivted with grss or mize on sndy soils in utumn 214. The results for grss nd mize were nlysed seprtely. These results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Derogtion crops on sndy lom soils Besides sndy soils, sndy lom soils re soil type on which derogtion is frequently requested. As for sndy soils the vrince in nitrte residue is lrge for both derogtion nd no derogtion prcels on sndy lom soils. On derogtion prcels the verge nitrte residue ws 55 ± 35 kg NO 3 -N/h nd 7 ± 53 kg NO 3 -N/h on no derogtion prcels. Due to the lrge rnge of nitrte residue on both types of prcels the difference between the verge nitrte residue ws not sttisticlly significnt (p =.54). 176

179 Nitrte-N (kg/h) 2,6 Derogtion crops on sndy lom soils 2,4 2,2 2, log(nitrte) 1,8 1,6 1,4 1,2 1,,8 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 15: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels for derogtion crops on sndy lom soils in utumn 214. SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 Derogtion No derogtion Figure 151: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels for derogtion crops on sndy lom soils in utumn 214. These results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Grss nd mize on sndy lom soils Grss nd mize re the most commonly grown derogtion crops on sndy lom soils. For these crops seprte sttisticl comprison is mde of derogtion nd no derogtion prcels. For grss 177

180 Nitrte-N (kg/h) (p =.9), nor for mize (p =.84) the nitrte residue of derogtion nd no derogtion prcels ws significntly different (Figure 152). The verge mount of nitrte-n on derogtion prcels with grss on sndy lom soils is 45 ± 36 kg NO 3 -N/h in utumn 214. On the prcels without derogtion cultivted with grss it is 46 ± 4 kg NO 3 -N/h. On the mize prcels with nd without derogtion the verge nitrte residue ws respectively 8 ± 28 kg NO 3 -N/h nd 88 ± 57 kg NO 3 -Nh ' ' cm cm cm 1 Derogtion No derogtion Derogtion No derogtion Grss Mïze Figure 152: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels cultivted with grss or mize on sndy lom soils in utumn 214. The results for grss nd mize were nlysed seprtely. These results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference Nitrte in utumn 214, prcels which were continuously under derogtion/no derogtion during In order to verify the long-term impct of derogtion on the nitrte residue, only the prcels which were continuously under derogtion/no derogtion during were retined for sttisticl nlysis. The following box plots show the vrition of the nitrte residue within the groups (derogtion nd no derogtion). The dt re log-trnsformed in order to obtin normlity of the dtset. All dt re shown visully in br grphs, which show the distribution of nitrte in the soil profile (- 3 cm, 3-6 cm, 6-9 cm). 178

181 On both derogtion nd no derogtion prcels, lrge vrition in nitrte residue in utumn 214 is noticed (Figure 153). The verge mount of nitrte-n on prcels continuously under derogtion since 29 is 6 ± 36 kg/h. On prcels continuously without derogtion it is 73 ± 57 kg/h (Figure 154). Since no limittion to derogtion crops, no sttisticl nlysis is crried out. 2,6 All crops on ll soil textures longterm derogtion/no derogtion 2,4 2,2 2, log(nitrte) Nitrte-N (kg/h) 1,8 1,6 1,4 1,2 1,,8 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 153: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels on ll soil textures in utumn 214, including only prcels which were continuously under derogtion/no derogtion during SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 derogtion no derogtion Figure 154: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 214 on ll soil textures, including only prcels which were continuously under derogtion/no derogtion during

182 Prcels continuously cultivted with or without derogtion conditions were compred seprtely for sndy nd sndy lom soils, since on these soil types derogtion is most frequently requested. Since on the prcels without derogtion lso no derogtion crops re grown in the period , no sttisticl nlysis is crried out. 2,6 Nitrte-N (kg/h) All crops on sndy soils longterm derogtion/no derogtion 2,6 All crops on sndy lom soils longterm derogtion/no derogtion 2,4 2,4 2,2 2,2 2, 2, log(nitrte) 1,8 log(nitrte) 1,8 1,6 1,6 1,4 1,4 1,2 1,2 1, Derogtion J No derogtion N Men Men±SE Men±2*SD 1,,8 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 155: Box plot of log(nitrte-n) for derogtion nd no derogtion prcels on sndy soils (left) nd sndy lom soils (right) in utumn 214, including only prcels which were continuously under derogtion/no derogtion during SE: stndrd error of the men. SD: stndrd devition. On sndy soils cultivted under derogtion conditions in the period , the verge nitrte residue in utumn 214 is 61 ± 39 kg N/h. On prcels cultivted without derogtion in this period the nitrte residue is 67 ± 49 kg N/h in utumn 214 (Figure 156) cm 3-6 cm 6-9 cm 2 1 derogtion no derogtion Figure 156: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 214 on sndy soils, including only prcels which were continuously under derogtion/no derogtion during

183 Nitrte-N (kg/h) On sndy lom soils cultivted under derogtion conditions in the period , the verge nitrte residue in utumn 214 is 59 ± 35 kg N/h. On prcels cultivted without derogtion in this period the nitrte residue is 81 ± 65 kg N/h in utumn 214 (Figure 157) derogtion no derogtion -3 cm 3-6 cm 6-9 cm Figure 157: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 214 on sndy lom soils, including only prcels which were continuously under derogtion/no derogtion during Limiting to derogtion crops cultivted in the period mkes sttisticl comprison of derogtion nd no derogtion prcels possible. On long-term derogtion prcels cultivted with derogtion crops the verge nitrte residue in utumn 214 is 6 ± 36 kg N/h. On prcels cultivted with derogtion crops without derogtion in the period the nitrte residue is 58 ± 43 kg N/h in utumn 214. The nitrte residue did not differ significntly (p =.3) (Figure 159). 181

184 2,6 Nitrte-N (kg/h) Derogtion crops on ll soil textures longterm derogtion/no derogtion 2,4 2,2 2, log(nitrte) 1,8 1,6 1,4 1,2 1,,8 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 158: Box plot of log(nitrte-n) in utumn 214 for derogtion nd no derogtion prcels cultivted with derogtion crops on ll soil textures, including only prcels which were continuously under derogtion/no derogtion during SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 derogtion no derogtion Figure 159: Averge nitrte-n (kg/h) in utumn 214 on derogtion nd no derogtion prcels cultivted with derogtion crops on ll soils, including only prcels which were continuously under derogtion/no derogtion during The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. Since sndy nd sndy lom soils re the soil textures on which derogtion is most frequently requested, comprison of continuous derogtion nd no derogtion prcels grown with derogtion crops, is mde seprtely for sndy nd sndy lom soils. 182

185 Nitrte-N (kg/h) On sndy soils cultivted with derogtion crops under derogtion conditions in the period , the verge nitrte residue in utumn 214 is 61 ± 39 kg N/h. On prcels cultivted without derogtion in this period the nitrte residue is 6 ± 35 kg N/h in utumn 214. Derogtion nd no derogtion prcels did not differ significntly (p =.82) (Figure 161). 2,4 Derogtion crops on sndy soils longterm derogtion/no derogtion 2,2 2, 1,8 log(nitrte) 1,6 1,4 1,2 1,,8 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 16: Box plot of log(nitrte-n) in utumn 214 for derogtion nd no derogtion prcels cultivted with derogtion crops on sndy soils, including only prcels which were continuously under derogtion/no derogtion during SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 derogtion no derogtion Figure 161: Averge nitrte-n (kg/h) in utumn 214 on derogtion nd no derogtion prcels cultivted with derogtion crops on sndy soils, including only prcels which were continuously under derogtion/no derogtion during The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 183

186 Nitrte-N (kg/h) On sndy lom soils cultivted with derogtion crops under derogtion conditions in the period , the verge nitrte residue in utumn 214 is 59 ± 35 kg N/h. On prcels cultivted without derogtion in this period the nitrte residue is 57 ± 34 kg N/h in utumn 214. Derogtion nd no derogtion prcels did not differ significntly (p =.7) (Figure 163). 2,4 Derogtion crops on sndy lom soils longterm derogtion/no derogtion 2,2 2, 1,8 log(ntrte) 1,6 1,4 1,2 1,,8 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 162: Box plot of log(nitrte-n) in utumn 214 for derogtion nd no derogtion prcels cultivted with derogtion crops on sndy lom soils, including only prcels which were continuously under derogtion/no derogtion during SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 2 1 derogtion no derogtion Figure 163: Averge nitrte-n (kg/h) in utumn 214 on derogtion nd no derogtion prcels cultivted with derogtion crops on sndy lom soils, including only prcels which were continuously under derogtion/no derogtion during The results were nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 184

187 Since grss is one of the most importnt derogtion crops, sttisticl comprison is mde for prcels continuously grown with grss or mize in the period , irrespective the soil texture. On prcels continuously grown with grss nd continuously under derogtion conditions the nitrte residue in utumn 214 is 54 ± 32 kg N/h (Figure 165). When cultivted without derogtion the nitrte residue on the prcels continuously cultivted with grss since 29, is 57 ± 56 kg N/h in utumn 214. Figure 164 shows tht the vrition in nitrte residue ws lrger on prcels without derogtion. No sttisticl difference between long term derogtion nd no derogtion grss prcels is detected (p =.37). 2,6 Long term grss prcels on ll soils longterm derogtion/no derogtion 2,4 2,2 2, 1,8 log(nitrte) 1,6 1,4 1,2 1,,8,6,4 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 164: Box plot of log(nitrte-n) in utumn 214 for derogtion nd no derogtion prcels on ll soil textures cultivted with grss, including only prcels which were continuously under derogtion/no derogtion during nd grown with grss. SE: stndrd error of the men. SD: stndrd devition. 185

188 Nitrte-N (kg/h) cm 3-6 cm 6-9 cm 2 1 derogtion no derogtion Figure 165: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 214 on ll soils, including only prcels which were continuously under derogtion/no derogtion during nd grown with grss. The results re nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the logtrnsformed dt. Identicl letters indicte no sttisticl difference. Since the number of prcels on which mize is cultivted every yer is too limited, no sttisticl comprison is done, but vrition is lrge on both types of prcels (Figure 166). 2,3 Long term mize prcels on ll soils longterm derogtion/no derogtion 2,2 2,1 2, 1,9 log(nitrte) 1,8 1,7 1,6 1,5 1,4 1,3 1,2 Derogtion J No Nderogtion Men Men±SE Men±2*SD Figure 166: Box plot of log(nitrte-n) in utumn 214 for derogtion nd no derogtion prcels cultivted with mize every yer on ll soil textures, including only prcels which were continuously under derogtion/no derogtion during SE: stndrd error of the men. SD: stndrd devition. 186

189 Nitrte-N (kg/h) On prcels every yer grown with mize nd continuously under derogtion conditions the nitrte residue in utumn 214 is 54 ± 25 kg N/h. When cultivted without derogtion the nitrte residue on the prcels yerly cultivted with mize since 29 is 62 ± 28 kg N/h in utumn 214 (Figure 167) derogtion no derogtion -3 cm 3-6 cm 6-9 cm Figure 167: Averge nitrte-n (kg/h) on derogtion nd no derogtion prcels in utumn 214 on ll soils, including only prcels which were continuously under derogtion/no derogtion during nd grown with mize. The results re nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 6.2 Nitrte in utumn 214 in the deeper soil lyer For selection of prcels n dditionl soil smple is tken from 9 to 12 cm (the deep soil smple ). In this soil lyer the mount of nitrte is mesured. In utumn 214 on 37 prcels deep soil smple ws tken. Dt re considered sttisticl outliers when exceeding the verge plus 2 times the stndrd devition. One outlier is removed, prcel on sndy soil cultivted with mize without derogtion. The mount of nitrte-n in the soil lyer 9-12 cm is 165 kg N/h. The soil profile from -9 cm contined only 3 kg N/h on this prcel. No exubernt fertilistion ws pplied nd yield ws good. A cover crop ws sown t October 1 st, 25 dys before smpling of the nitrte residue. Like in utumn 213 significnt correltion (p=.) is found between the mount of nitrte in the soil profile from -9 cm nd the mount of nitrte in the soil profile from 9-12 cm (Figure 168). 187

190 12 Nitrte in the soil profile in utumn 214 Y = 6,1544+,323*x; R²=.52; p= cm cm Figure 168: Sctterplot of the nitrte-n (kg/h) in the soil profile from -9 cm versus the nitrte-n (kg/h) in the soil profile from 9-12 cm in utumn 214. Since the deep soil smples re tken on selection of prcels, it is not possible to crry out sttisticl nlysis for ll combintions of derogtion, soil texture nd cultivted crop. The comprison is limited to grss nd mize on ll soil textures, bsed on box plot of the logtrnsformed dt (Figure 169 nd Figure 17). 2,4 Grss-ll soils 2,2 Mize-ll soils 2,2 2, 2, 1,8 1,8 log(nitrte) ,6 1,4 1,2 1, log(nitrte) ,6 1,4 1,2,8 1,,6,4,2 Derogtion J No derogtion N Men Men±SE Men±2*SD,8,6 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 169: Box plot of log(nitrte-n, 9-12 cm) for derogtion nd no derogtion prcels in utumn 214, for grss (left) nd mize (right) on ll soil textures. SE: stndrd error of the men. SD: stndrd devition. 188

191 Nitrte-N (kg/h) The verge level of nitrte-n in the soil lyer 9-12 cm on prcels cultivted with grss under derogtion is 34 ± 24 kg/h nd 11 ± 8 kg/h without derogtion. The verge level of nitrte-n in the soil lyer 9-12 cm on prcels cultivted with mize under derogtion is 21 ± 2 kg/h nd 27 ± 27 without derogtion. In the soil profile till 12 cm, the verge level of nitrte-n is 89 ± 57 kg/h on derogtion prcels nd 44 ± 24 kg/h on no derogtion prcels. On prcels cultivted with mize the mount of nitrte-n in the soil profile -12 cm is 59 ± 19 kg/h with derogtion nd 79 ± 38 kg/h without derogtion. 2,6 Grss-ll soils 2,4 Mize-ll soils 2,4 2,3 2,2 2,2 2,1 log(nitrte) -12 2, 1,8 1,6 log(nitrte) -12 2, 1,9 1,8 1,7 1,4 1,6 1,5 1,2 1, Derogtion J No Nderogtion Men Men±SE Men±2*SD 1,4 1,3 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 17: Box plot of log(nitrte-n, 9-12 cm) for derogtion nd no derogtion prcels in utumn 214, for grss (left) nd mize (right) on ll soil textures. SE: stndrd error of the men. SD: stndrd devition cm 3-6 cm 6-9 cm 9-12 cm 2 Derogtion No derogtion Grss Derogtion No derogtion Mïze Figure 171: Averge nitrte-n (kg/h) in the 4 soil lyers on derogtion nd no derogtion prcels on ll soil textures cultivted with grss or mize, utumn

192 6.21 Nitrte in the deeper soil lyer Since the deep soil smple is tken on selection of prcels, rther limited number of dt is vilble t ech smpling moment. Therefore sttisticl nlysis is performed on ll dt of ll smpling moments. For this nlysis outliers were detected in the whole group, not s n outlier per smpling moment. As such 5 vlues were detected s sttisticl outlier. The first outlier ws detected in spring 212, the mount of nitrte-n in the soil lyer 9-12 cm ws 186 kg N/h. The mount of nitrte-n in the profile -9 cm ws 96 kg/h (14, 27 nd 55 kg N/h in the soil lyers -3 cm, 3-6 cm nd 6-9 cm). The prcel ws cultivted with mize in 211 nd hd high nitrte residue in utumn 211, 269 kg N/h (166, 7 nd 33 kg N/h in the soil lyers -3 cm, 3-6 cm nd 6-9 cm). The lrge mount of nitrte-n in the deep soil lyer ws clerly the result of nitrte leching out the soil profile -9 cm during winter Three outliers were mesurements of utumn 212. One prcel ws cultivted with pottoes in 212. In the soil lyer 9-12 the mount of nitrte-n ws 352 kg/h. In the soil profile bove 134 kg N/h ( ) ws mesured. Another prcel ws cultivted with spinch nd leek, which hd no high nitrte residue in the soil lyer -9 cm (3 kg N/h) but 134 kg N/h in the soil lyer 9-12 cm. The third prcel ws converted from grss lnd into rble lnd (mize) in spring 211. Nitrte ws distributed in the soil profile till 12 cm per soil lyer of 3 cm s follows: kg N/h. The fifth vlue detected s outlier ws smple of utumn 214. A mize prcel with norml nitrte residue (3 kg N/h, -9 cm), good yield nd no exubernt fertilistion but high mount of nitrte-n in the soil lyer 9-12 cm: 165 kg N/h. As done t ech smpling moment, the correltion between the nitrte-n content in the soil lyers -9 cm nd 9-12 cm is shown. The correltion between the mount of nitrte in the soil profile from -9 cm nd the mount of nitrte in the soil lyer 9-12 cm is significnt (p =.), but the regression explins only 27 % of the vrince. Both for derogtion (p =.) nd no derogtion prcels (p =.) seprtely, the correltion is sttisticlly significnt. Even though the models explins only 16 % (derogtion prcels) nd 35 % (no derogtion prcels) of the vrince (Figure 172). 19

193 14 Nitrte in the soil profile utumn 211-utumn 214 Y = *x; R²=.2691; p=. Y (dero) = *x; R²=.1599; p=. Y (non dero) = *x; R²=.3472; p= cm cm Dero 9-12 non dero Figure 172: Sctterplot of the nitrte-n (kg/h) in the soil profile from -9 cm versus the nitrte-n (kg/h) in the soil profile from 9-12 cm , for ll prcels (blue), derogtion prcels (red) nd no derogtion prcels (green). On prcels cultivted with derogtion crops, no sttisticl significnt difference exists between the mount of nitrte-n in the soil lyer 9-12 cm of derogtion nd no derogtion prcels (p=.58) (Figure 173). In the soil lyer 9-12 cm the mount of nitrte-n is 27 ± 25 kg/h on derogtion prcels nd 26 ± 24 kg/h on no derogtion prcels. On grss prcels cultivted under derogtion conditions the level of nitrte-n in the soil lyer 9-12 cm ws 26 ± 26 kg/h. On grss prcels cultivted without derogtion this mount ws 18 ± 16 kg/h. Due to vrition there ws no sttisticl significnt difference between derogtion nd no derogtion grss prcels (p =.7) (Figure 174). 191

194 2,2 Derogtion crops, ll soils 2, 1,8 log(nitrte) 9-12cm 1,6 1,4 1,2 1,,8,6,4 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 173: Box plot of log(nitrte-n, 9-12 cm, ) for derogtion nd no derogtion prcels cultivted with derogtion crops on ll soil textures. SE: stndrd error of the men. SD: stndrd devition. 2,2 Grss, ll soils 2, 1,8 1,6 log(nitrte) 9-12cm 1,4 1,2 1,,8,6,4,2 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 174: Box plot of log(nitrte-n, 9-12 cm, ) for derogtion nd no derogtion prcels cultivted with derogtion crops on ll soil textures. SE: stndrd error of the men. SD: stndrd devition. 192

195 On mize prcels the mount of nitrte-n in the soil lyer 9-12 ws 3 ± 23 kg/h on derogtion prcels nd 34 ± 28 kg/h on no derogtion prcels. As for grss no sttisticl difference in nitrte-n in the soil lyer 9-12 cm is found on mize prcels (p =.45) (Figure 175). 2,2 Mize, ll soils 2, 1,8 log(nitrte) 9-12cm 1,6 1,4 1,2 1,,8,6,4 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 175: Box plot of log(nitrte-n, 9-12 cm, ) for derogtion nd no derogtion prcels cultivted with derogtion crops on ll soil textures. SE: stndrd error of the men. SD: stndrd devition. The lck of sttisticl significnt differences in the mount of nitrte-n in the soil lyer 9-12 cm between derogtion nd no derogtion prcels cultivted with grss ws lso reveled on sndy (p =.9) nd sndy lom (p =.17) soils (Figure 176). The sme ws done for prcels cultivted with mize on sndy (p =.14) nd sndy lom (p =.6) soils (Figure 177). 193

196 2,2 Grss on sndy soils 2,2 Grss on sndy lom soils 2, 2, 1,8 1,8 1,6 1,6 log(nitrte) 9-12cm 1,4 1,2 1, log(nitrte) 9-12cm 1,4 1,2 1,,8,8,6,6,4,4,2 Derogtion J No derogtion N Men Men±SE Men±2*SD,2, Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 176: Box plot of log(nitrte-n, 9-12 cm, ) for derogtion nd no derogtion prcels cultivted with grss on sndy soils (left) nd sndy lom soils (right). SE: stndrd error of the men. SD: stndrd devition. 2,4 Mize on sndy soils 2,4 Mize on sndy lom soils 2,2 2,2 2, 2, log(nitrte) 9-12cm 1,8 1,6 1,4 1,2 1, log(nitrte) 9-12cm 1,8 1,6 1,4 1,2,8 1,,6,4 Derogtion J No Nderogtion Men Men±SE Men±2*SD,8,6 Derogtion J No Nderogtion Men Men±SE Men±2*SD Figure 177: Box plot of log(nitrte-n, 9-12 cm, ) for derogtion nd no derogtion prcels cultivted with mize on sndy soils (left) nd sndy lom soils (right). SE: stndrd error of the men. SD: stndrd devition. Since no sttisticl significnt differences re found between derogtion nd no derogtion prcels for the mount of nitrte-n in the soil lyers -9 cm nd 9-12 no sttisticl differences re expected for the soil profile -12 cm. Comprison of the mount of nitrte-n in the soil profile -12 cm, bsed on ll smpling dt in the period , shows on derogtion nd no derogtion prcels cultivted with derogtion crops similr vrition (Figure 178). On prcels cultivted with derogtion crops the mount of nitrte-n in the soil profile -12 cm is 76 ± 65 kg/h on derogtion prcels nd 74 ± 66 kg/h on no derogtion prcels (Figure 179). This difference is not sttisticl significnt (p =.74). 194

197 Nitrte-N (kg/h) 2,6 Derogtion crops, ll soils 2,4 2,2 log(nitrte) -12cm 2, 1,8 1,6 1,4 1,2 1, Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 178: Box plot of log(nitrte-n, -12 cm, ) for derogtion nd no derogtion prcels cultivted with derogtion crops on ll soil textures. SE: stndrd error of the men. SD: stndrd devition cm 6-9 cm derogtion no derogtion Figure 179: Averge nitrte-n (kg/h) ( ) in the 4 soil lyers on derogtion nd no derogtion prcels cultivted with derogtion crops on ll soil textures. The results re nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. Focus on the most importnt derogtion crops nd soil textures on which derogtion is most requested, results in the sme conclusion. 195

198 Nitrte-N (kg/h) On grss prcels on sndy soils the soil lyer -12 cm contins in verge 66 ± 58 kg N/h when cultivted under derogtion nd 6 ± 46 kg N/h when cultivted without derogtion (p =.62) (Figure 18 nd Figure 181). On grss prcels on sndy lom soils the soil lyer -12 cm contins in verge 53 ± 29 kg N/h when cultivted under derogtion nd 35 ± 1 kg N/h when cultivted without derogtion (p =.7) (Figure 18 nd Figure 183). 2,4 Grss on sndy soils 2,2 Grss on sndy lom soils 2,2 2, 2, log(nitrte) -12 cm 1,8 1,6 1,4 1,2 log(nitrte) -12cm 1,8 1,6 1,4 1,,8 Derogtion J No derogtion N Men Men±SE Men±2*SD 1,2 1, Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 18: Box plot of log(nitrte-n, -12 cm, ) for derogtion nd no derogtion prcels cultivted with grss on sndy soils (left) nd sndy lom soils (right). SE: stndrd error of the men. SD: stndrd devition ' ' cm 3-6 cm 6-9 cm derogtion no derogtion derogtion no derogtion Grss Mïze Figure 181: Averge nitrte-n (kg/h) ( ) in the 4 soil lyers on derogtion nd no derogtion prcels cultivted with grss or mize on sndy soils. The results re nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 196

199 On mize prcels on sndy soils the soil lyer -12 cm contins in verge 95 ± 81 kg N/h when cultivted under derogtion nd 11 ± 12 kg N/h when cultivted without derogtion (p =.75) (Figure 181 nd Figure 182). On mize prcels on sndy lom soils the soil lyer -12 cm contins in verge 1 ± 78 kg N/h when cultivted under derogtion nd 19 ± 59 kg N/h when cultivted without derogtion (p =.42) (Figure 182 nd Figure 183). 2,8 Mize on sndy soils 2,8 Mize on sndy lom soils 2,6 2,6 2,4 2,4 log(nitrte) -12cm 2,2 2, 1,8 1,6 log(nitrte) -12cm Nitrte-N (kg/h) 2,2 2, 1,8 1,6 1,4 1,4 1,2 1,2 1, Derogtion J No derogtion N Men Men±SE Men±2*SD 1,,8 Derogtion J No Nderogtion Men Men±SE Men±2*SD Figure 182: Box plot of log(nitrte-n, -12cm, ) for derogtion nd no derogtion prcels cultivted with mize on sndy soils (left) nd sndy lom soils (right). SE: stndrd error of the men. SD: stndrd devition ' ' 8-3 cm cm 6-9 cm derogtion no derogtion derogtion no derogtion Grss Mïze Figure 183: Averge nitrte-n (kg/h) ( ) in the 4 soil lyers on derogtion nd no derogtion prcels cultivted with grss or mize on sndy lom soils. The results re nlysed sttisticlly by mens of one-wy ANOVA (p.5) on the log-trnsformed dt. Identicl letters indicte no sttisticl difference. 197

200 6.22 Conclusion There is no significnt difference for nitrte-n (kg/h) in the soil profile (-9 cm) between derogtion nd no derogtion prcels cultivted with derogtion crops (on ll soil textures, sndy soils or sndy lom soils), cultivted with grss (on sndy soils or sndy lom soils) nd prcels cultivted with mize (on sndy soils or sndy lom soils) t the smpling moments in the period utumn 211-utumn 214. At ny of the smpling moments sttisticl significnt differences in the mount of nitrte-n between derogtion nd derogtion prcels re mesured. Even for prcels continuously under derogtion/no derogtion in the period , there is no significnt difference for nitrte-n (kg/h) in the soil profile (-9 cm). The nitrte in the soil profile (-9 cm) nd the nitrte in the deep soil lyer (9-12 cm) re often significntly correlted. Derogtion hs no effect on the mount of nitrte-n in the deeper soil lyer of 9-12 cm. No sttisticl difference is shown between derogtion nd no derogtion prcels for the nitrte-n in the deeper soil lyer. 7 Nitrte in the surfce nd groundwter The purpose of this study is to determine if derogtion hs possible effect on wter qulity. Therefore different wter smples relted to the prcels of the monitoring network re tken nd different prmeters re mesured. In the wter smples nitrte is one of the most importnt prmeters to determine if derogtion prcels hve negtive impct on the wter qulity in comprison with no derogtion prcels. 7.1 Cnls, ditches nd drins Some prcels of the network re linked to cnl or ditch, or re drined. An overview of the number of prcels of which wter smple is tken from cnl, ditch or drin is shown in Tble 49. In utumn 211 nd spring 212 for 24 nd 25 prcels respectively, wter smple is tken from cnl, ditch or drin, compred with 37 prcels in utumn 212. The low number of mesurements in utumn 211 nd spring 212 is the result of dry cnls, drins or ditches. Therefore on these sites no wter smple ws obtined. 198

201 Tble 49: Overview of the number of prcels for which wter smple is tken from cnl, ditch or drin. Number of prcels Autumn Spring Autumn Spring Autumn Spring Autumn These smples could give n indiction of the surfce wter qulity. However, the link between the smpling point for the surfce wter nd prticulr prcel of the monitoring network is not lwys very cler. Especilly cnls nd ditches my be influenced by more thn one prcel or by other non-griculturl prctices. Moreover, the concentrtions of nitrte in the wter smples of drins, cnls nd ditches re influenced by the moment of smpling (recent rinfll) with vribility in the results s consequence. Therefore the concentrtions of nitrte in the wter smples of drins, cnls nd ditches re rther indictive. The verge mount of nitrte mesured in the wter smples is shown in Tble 5. Becuse of the drought in utumn 211, mny drins were dry. Low concentrtions of nitrte were mesured in drins, cnls nd ditches in utumn 211. Becuse of the drought, little nitrogen hd leched out into the wter. It needs to be noted tht in utumn 211, 11 of the 24 wter smples hd nitrte content below the detection limit. The nitrte concentrtion ws lower in utumn 211 (before winter) thn in spring 212 (fter winter). This mens tht fter winter, possibly prt of the nitrte from the soil hs leched out into drins, cnls nd ditches. However, since only few prcels re mesured, no ANOVA nlysis ws crried out. In utumn 212, two prcels hd very high nitrte concentrtion (one in drin, one in cnl or ditch). The prcel linked to cnl or ditch with high nitrte concentrtion in utumn 212, lso hd high nitrte concentrtion in spring 212 (15 mg NO 3 /l). In utumn 211, this prcel hd nitrte concentrtion of.22 mg NO 3 /l. Since more prcels my influence one cnl or ditch, it is not esy to link the fertilistion- nd mngement prctices to one prcel. 199

202 Tble 5: Averge vlues of nitrte (mg NO 3/l) mesured in wter smples tken from the surfce wter linked to specific prcels of the monitoring network. Distinction is mde between derogtion nd no derogtion prcels. The number of prcels is indicted by n. n Nitrte (mg/l) (min-mx) Autumn 211 Drins Derogtion - - No derogtion 2 dl (dl, dl) Cnls nd ditches Derogtion 14 1 (dl, 4) No derogtion 8 1 (dl, 3) Spring 212 Drins Derogtion 3 15 (dl, 27) No derogtion 1 dl dl Cnls nd ditches Derogtion (dl, 15) No derogtion 1 9 (dl, 33) Autumn 212 Drins Derogtion 6 61 (dl, 196) No derogtion 6 22 (.9, 84) Cnls nd ditches Derogtion (dl, 151) No derogtion 9 3 (dl, 13) Spring 213 Drins Derogtion 6 26 (dl, 8) No derogtion 6 37 (9, 15) Cnls nd ditches Derogtion (dl, 75) No derogtion 9 2 (dl, 4) Autumn 213 Drins Derogtion 3 74 (dl, 137) No derogtion 2 22 (9, 43) Cnls nd ditches Derogtion (dl, 157) No derogtion (dl, 84) Spring 214 Drins Derogtion 3 36 (.41-64) No derogtion 5 3 (4.6-7) Cnls nd ditches Derogtion (dl-145) No derogtion 1 27 (dl-172) Autumn 214 Drins Derogtion - - No derogtion 2 4 (1.5-7) Cnls nd ditches Derogtion 16 7 (dl-55) No derogtion 16 1 (dl-44) 2

203 The derogtion prcel with very high nitrte concentrtion in utumn 212 in drin (196 mg NO 3 /l) ws cultivted with mize nd hd low nitrte concentrtion in utumn 212 in the soil (27 kg NO 3 -N/h). In spring 213, one prcel hd very high nitrte concentrtion in drin of 15 mg NO 3 /l. In utumn 212, the nitrte concentrtion in this drin ws 84 mg NO 3 /l. In spring 212 nd utumn 211 however, the drin hd nitrte concentrtion below detection limit. In utumn 213 two prcels with high nitrte concentrtion in the surfce wter were detected. At drin 137 mg NO 3 /l ws mesured nd 157 mg NO 3 /l ws mesured in ditch. In spring 214 high nitrte concentrtion of 145 mg NO 3 /l ws mesured in the ditch with high nitrte concentrtion in utumn 213. In utumn 214 no high levels of nitrte is surfce wter re mesured. In cnls nd ditches the verge concentrtion is 7 mg NO 3 /l for derogtion prcels nd 1 mg NO 3 /l for no derogtion prcels. These verge vlues re with the lowest verge vlues mesured since utumn 211. Only in utumn 211 these vlues were smller. Of the wter smples tken t drin, the nitrte concentrtion of 1 smple ws below detection limit. Of the wter smples tken in ditch or cnl, t derogtion nd no derogtion prcels, in 4 nd 5 smples, nitrte concentrtion ws below detection limit. The qulity threshold of nitrte in the groundwter is 5 mg NO 3 /l. The verge vlues shown in Tble 5 re ll below this vlue, except for drins in utumn 212, where the verge nitrte ws 61 mg NO 3 /l, nd drins in utumn 213, where the verge concentrtion ws 74 mg NO 3 /l. When looking more in detil to the minimum nd mximum vlues, some drins, cnls nd ditches regulrly exceed the limit of 5 mg NO 3 /l. Due to the low number of smples (especilly for drins) it is not desirble to compre derogtion nd no derogtion prcels sttisticlly. Moreover, the mesurements of the different smples re often highly vrible, s cn be seen from the minimum nd mximum vlues in Tble 5. Vribility of the mesurements t ech moment of smpling nd for both derogtion nd no derogtion prcels is shown in Figure 184. Figure 185 shows lso the vribility of the mesurement but even demonstrtes by the position of the medin tht lrge number of mesurements is situted ner detection limit. 21

204 22 Sctterplot nitrte concentrtion surfce wter Nitrte (mg/l) utumn 211 utumn 212 utumn 213 utumn 214 spring 212 spring 213 spring 214 Derogtion No derogtion Figure 184: Sctterplot of the nitrte concentrtion (mg NO 3/l) in the surfce wter t drins, cnls nd ditches t derogtion nd no derogtion prcels for ech moment of smpling. 22 Nitrte concentrtion surfce wter Nitrte (mg/l) utumn 211 utumn 212 utumn 213 utumn 214 spring 212 spring 213 spring 214 Medin 25%-75% Min-Mx Figure 185: Boxplot of the nitrte concentrtion (mg NO 3/l) in the surfce wter t drins, cnls nd ditches for ech moment of smpling. 22

205 7.2 Shllow groundwter (MAP smpling points groundwter nd monitoring wells) Another prmeter to mesure the possible impct of derogtion on the wter qulity is the nitrte concentrtion in MAP smpling points groundwter nd monitoring wells (shllow groundwter). The wter qulity mesured in these smpling points is minly influenced by single griculturl prcel nd could therefore be linked to the chrcteristics (fertilistion prctices nd cultivted crop) of this prcel. The dt of nitrte in the monitoring wells for 29_utumn, 21_spring, 21_utum nd 211_spring were obtined from the report Estblishment nd follow-up of monitoring network of frmers to ssess the impct of derogtion on the wter qulity (Vndervelpen et l., 211). Tble 51: Averge nitrte concentrtion (mg NO 3/l) in the MAP (M) smpling points nd monitoring wells (W) linked to prcel of the monitoring network for different yers. For ech yer the number of prcels is indicted by n. Nitrte (mg/l) n M (min, mx) n W (min, mx) 29_utumn (dl, 26) (dl, 32) 21_spring (dl, 22) (dl, 22) 21_ utumn (dl, 18) (dl, 224) 211_ spring (dl, 21) (dl, 159) 211_ utumn (dl, 216) (dl, 195) 212_ spring (dl, 167) (dl, 125) 212_ utumn (dl, 18) (dl, 192) 213_ spring 1 29 (dl, 22) (dl, 132) 213_ utumn 9 27 (dl, 237) (dl, 147) 214_ spring (dl, 141) 214_utumn (dl, 139) dl: detection limit (.2 mg/l nitrte for groundwter). For the smples below detection limit, hlf of the detection limit (.1 mg nitrte/l) is used for clcultions. The verge nitrte concentrtions t both monitoring wells nd MAP smpling points re rther stble since utumn 29. The verge vlues re t ech moment of smpling below the qulity threshold of 5 mg NO 3 /l in the groundwter. As the minim nd mxim show, the vribility in nitrte concentrtion t both MAP smpling points nd monitoring wells ws lrge. The nitrte concentrtion ws often below detection limit but other monitoring wells or MAP smpling points regulrly exceeded the qulity threshold. 23

206 In the next prgrphs, the estimted trvel time of wter from specific prcel to the smpling point or monitoring well ws used to link prcel chrcteristics (derogtion nd cultivted crop) to wter mesurements in the MAP smpling point or monitoring well of specific yer. For exmple, for the prcel chrcteristics of 29, if wter of one prcel hd trvel time of 1 yer, the wter mesurements in the smpling point of monitoring well of 21 ws used. This wy, the impct of derogtion on nitrte in shllow groundwter cn be determined Prcel chrcteristics of 29 Bsed on the trvel time, wter smples from utumn nd spring of 29, 21, 211 or 212 were linked to the prcel chrcteristics of 29. For exmple, if the trvel time is 1.13 yers, the wter smple of spring 21 is linked to the prcel chrcteristics of 29. A one-wy ANOVA (p.5) test ws crried out on the log-trnsformed dt in order to verify significnt differences between derogtion nd no derogtion prcels. There is no significnt effect of derogtion in 29 on the nitrte in the monitoring points (Tble 52). Tble 52: Averge nitrte (mg/l) of monitoring points linked (bsed on the trvel time) to the prcel chrcteristics of 29. The number of prcels is indicted by n, the number of prcels with nitrte vlue below detection limit is indicted by < dl. A one-wy ANOVA test (p.5) ws crried out on the log-trnsformed dt. Nitrte (mg/l) Derogtion No derogtion n verge (min, mx) <dl n verge (min, mx) <dl p-vlue All crops (dl, 21) (dl, 18) 2 Derogtion crops (dl, 21) (dl, 15) Grss (dl, 14) (dl, 92) 5.16 Mize (dl, 21) (dl, 15) 5.43 dl: detection limit (.2 mg/l nitrte for groundwter). For the smples below detection limit, hlf of the detection limit (.1 mg nitrte/l) is used for clcultions. The percentges of smpling points in specific rnge of nitrte concentrtion re given for derogtion nd no derogtion prcels seprtely in Figure 186 to Figure 189. For prcels cultivted with ll crops nd on ll soil textures, 86 % of smpling points linked to derogtion prcels hve nitrte concentrtion below 5 mg/l while 81 % of smpling points linked to no derogtion prcels hve nitrte concentrtion below 5 mg/l (Figure 186). For prcels cultivted with derogtion crops on ll soil textures, 86 % of smpling points linked to derogtion 24

207 Percentge of smpling points Percentge of smpling points prcels hve nitrte concentrtion below 5 mg/l while 8 % of smpling points linked to no derogtion prcels hve nitrte concentrtion below 5 mg/l (Figure 187) D: 86% ND: 81% 3 2 Derogtion No derogtion 1 < >1 Nitrte (mg/l) Figure 186: Percentge of smpling points in specific rnge of nitrte (mg/l) linked to the prcel chrcteristics of 29 for ll crops, bsed on the trvel time. The red verticl line indictes the qulity threshold of 5 mg/l D: 86% ND: 8% 3 2 Derogtion No derogtion 1 < >1 Nitrte (mg/l) Figure 187: Percentge of smpling points in specific rnge of nitrte (mg/l) linked to the prcel chrcteristics of 29 cultivted with derogtion crops, bsed on the trvel time. The red verticl line indictes the qulity threshold of 5 mg/l. 25

208 Percentge of smpling points Percentge of smpling points D: 94% ND: 83% 3 2 Derogtion No derogtion 1 < >1 Nitrte (mg/l) Figure 188: Percentge of smpling points in specific rnge of nitrte (mg/l) linked to the prcel chrcteristics of 29 cultivted with grss, bsed on the trvel time. The red verticl line indictes the qulity threshold of 5 mg/l D: 78% ND: 81% 3 2 Derogtion No derogtion 1 < >1 Nitrte (mg/l) Figure 189: Percentge of smpling points in specific rnge of nitrte (mg/l) linked to the prcel chrcteristics of 29 cultivted with mize, bsed on the trvel time. The red verticl line indictes the qulity threshold of 5 mg/l. 26

209 For prcels cultivted with grss on ll soil textures, 94 % of smpling points linked to derogtion prcels hve nitrte concentrtion below 5 mg/l while 83 % of smpling points linked to no derogtion prcels hve nitrte concentrtion below 5 mg/l (Figure 188). For prcels cultivted with mize on ll soil textures, 78 % of smpling points linked to derogtion prcels hve nitrte concentrtion below 5 mg/l while 81 % of smpling points linked to no derogtion prcels hve nitrte concentrtion below 5 mg/l (Figure 189). A lrge vrition exists between the smpling points nd in some of the smpling points (linked to both derogtion nd no derogtion prcels) very high concentrtions (> 1 mg/l) re mesured. Tble 53 shows the nitrte residue in 29 nd the nitrte concentrtion in groundwter linked to the prcel chrcteristics of 29 bsed on the trvel time. It is very importnt to notice tht the nitrte concentrtion in the groundwter is not only influenced by the nitrte residue. Other prmeters tht influence the effect of the nitrte residue on the nitrte concentrtion in the groundwter re the concentrtion of nitrte in the profile t -9 cm nd the process fctor s discussed in prgrph 14. Tble 53: Averge nitrte residue in 29 (kg N/h) nd verge nitrte concentrtion in groundwter (mg NO 3/l) of monitoring points linked (bsed on the trvel time) to the prcel chrcteristics of 29. Derogtion No derogtion Nitrte residue (kg N/h) Nitrte (mg/l) Nitrte residue (kg N/h) Nitrte (mg/l) verge (min, mx) verge (min, mx) verge (min, mx) verge (min, mx) All crops 82 (11, 283) 26 (dl, 21) 12 (14, 464) 24 (dl, 18) Derogtion crops 82 (11, 283) 26 (dl, 21) 78 (14, 195) 24 (dl, 15) Grss 69 (11, 283) 12 (dl, 14) 59 (14, 141) 21 (dl, 92) Mize 97 (32, 216) 39 (dl, 21) 83 (27, 161) 23 (dl, 15) For derogtion crops nd more specificlly for grss nd mize no significnt differences between derogtion nd no derogtion prcels were found, not in nitrte residue (see Vndervelpen et l., 211) nor in nitrte mesured in the wter (Tble 52). 27

210 7.2.2 Prcel chrcteristics of 21 Bsed on the trvel time, wter smples from utumn of 21, utumn nd spring of 211, 212 or 213 were linked to the prcel chrcteristics of 21. A sttisticl nlysis ws conducted by mens of one-wy ANOVA (p.5) of the log-trnsformed dt. No sttisticl nlysis ws conducted for ll crops, since no derogtion crops re present in this dtset nd therefore the compred groups re not homogeneous. Tble 54: Averge nitrte (mg/l) of monitoring points linked (bsed on the trvel time) to the prcel chrcteristics of 21. The number of prcels is indicted by n. A one-wy ANOVA (p.5) ws crried out between derogtion nd no derogtion prcels bsed on the log-trnsformed dt. Nitrte (mg/l) Derogtion No derogtion n verge (min, mx) <dl n verge (min, mx) <dl p-vlue All crops (dl, 156) (dl, 216) 15 - Derogtion crops (dl, 156) (dl, 216) 5.2 Grss 4 17 (dl, 156) (dl, 216) 5.23 Mize (dl, 87) (dl, 155) 9.5 dl: detection limit (.2 mg/l nitrte for groundwter). For the smples below detection limit, hlf of the detection limit (.1 mg nitrte/l) is used for clcultions. There is significnt effect of derogtion on nitrte in the monitoring points for derogtion crops nd mize on ll soils (Tble 54) bsed on one-wy ANOVA (p.5) of the logtrnsformed dt. From Tble 54 cn be seen tht lrge number of wter smples hve nitrte concentrtion below the detection limit. The percentges of smpling points in specific rnge of nitrte concentrtion re given for derogtion nd no derogtion prcels seprtely in Figure 19 to Figure 193. For prcels cultivted with ll crops nd on ll soil textures, 86 % of smpling points linked to derogtion prcels hve nitrte concentrtion below 5 mg/l while 82 % of smpling points linked to no derogtion prcels hve nitrte concentrtion below 5 mg/l (Figure 19). For prcels cultivted with derogtion crops on ll soil textures, 86 % of smpling points linked to derogtion prcels hve nitrte concentrtion below 5 mg/l while 82 % of smpling points linked to no derogtion prcels hve nitrte concentrtion below 5 mg/l (Figure 191). For prcels cultivted with grss on ll soil textures, 88 % of smpling points linked to derogtion prcels hve nitrte concentrtion below 5 mg/l while 89 % of smpling points linked to no derogtion prcels hve nitrte concentrtion below 5 mg/l (Figure 192). 28

211 Percentge of smpling points Percentge of smpling points D: 86% ND: 82% 3 2 Derogtion No derogtion 1 < >1 Nitrte (mg/l) Figure 19: Percentge of smpling points in specific rnge of nitrte (mg/l) linked to the prcels of 21 for ll crops, bsed on the trvel time. The red verticl line indictes the qulity threshold of 5 mg/l D: 86% ND: 82% 3 2 Derogtion No derogtion 1 < >1 Nitrte (mg/l) Figure 191: Percentge of smpling points in specific rnge of nitrte (mg/l) linked to the prcels of 21 cultivted with derogtion crops, bsed on the trvel time. The red verticl line indictes the qulity threshold of 5 mg/l. For prcels cultivted with mize on ll soil textures, 88 % of smpling points linked to derogtion prcels hve nitrte concentrtion below 5 mg/l while 81 % of smpling points linked to no derogtion prcels hve nitrte concentrtion below 5 mg/l (Figure 193). A lrge 29

212 Percentge of smpling points Percentge of smpling points vrition exists between the smpling points nd in some of the smpling points (linked to both derogtion nd no derogtion prcels) very high concentrtions (> 1 mg/l) re mesured D: 88% ND: 84% 3 2 Derogtion No derogtion 1 < >1 Nitrte (mg/l) Figure 192: Percentge of smpling points in specific rnge of nitrte (mg/l) linked to the prcels of 21 cultivted with grss, bsed on the trvel time. The red verticl line indictes the qulity threshold of 5 mg/l D: 88% ND: 81% 3 2 Derogtion No derogtion 1 < >1 Nitrte (mg/l) Figure 193: Percentge of smpling points in specific rnge of nitrte (mg/l) linked to the prcels of 21 cultivted with mize, bsed on the trvel time. The red verticl line indictes the qulity threshold of 5 mg/l. 21

213 Tble 55 shows the nitrte residue in 21 nd the nitrte concentrtion in groundwter linked to the prcel chrcteristics of 21 bsed on the trvel time. It is very importnt to notice tht the nitrte concentrtion in the groundwter is not only influenced by the nitrte residue. Other prmeters tht influence the effect of the nitrte residue on the nitrte concentrtion in the groundwter re the concentrtion of nitrte in the profile t -9 cm nd the process fctor s discussed in prgrph 14. Tble 55: Averge nitrte residue in 21 (kg N/h) nd verge nitrte concentrtion in groundwter (mg NO 3/l) of monitoring points linked (bsed on the trvel time) to the prcel chrcteristics of 21. Derogtion No derogtion Nitrte residue (kg N/h) Nitrte (mg/l) Nitrte residue (kg N/h) Nitrte (mg/l) verge (min, mx) verge (min, mx) verge (min, mx) verge (min, mx) All crops 59 (8, 185) 17 (dl, 156) 64 (8, 319) 28 (dl, 216) Derogtion crops 59 (8, 185) 17 (dl, 156) 63 (8, 319) 27 (dl, 216) Grss 47 (8, 163) 17 (dl, 156) 39 (8, 126) 26 (dl, 216) Mize 82 (9, 185) 14 (dl, 87) 8 (9, 319) 28 (dl, 155) Prcel chrcteristics of 211 Bsed on the trvel time, wter smples from utumn of 211, utumn nd spring of 212 nd 213 or spring 214 were linked to the prcel chrcteristics of 211. This comprison cnnot be finished since wter smples until spring 214 re therefore needed. For the MAP smpling points only the mesurements until utumn 213 re published nd mesurements of spring 214 re not vilble yet. Tble 56: Averge nitrte (mg/l) of monitoring points linked (bsed on the trvel time) to the prcel chrcteristics of 211. The number of prcels is indicted by n. A one-wy ANOVA (p.5) ws crried out between derogtion nd no derogtion prcels bsed on the log-trnsformed dt. Nitrte (mg/l) Derogtion No derogtion n verge (min, mx) <dl n verge (min, mx) <dl p-vlue All crops (dl, 18) (dl, 19) 19 - Derogtion crops (dl, 18) (dl, 19) Grss (dl, 131) (dl, 69) 7.8 Mize (dl, 18) (dl, 19) 7.88 dl: detection limit (.2 mg/l nitrte for groundwter). For the smples below detection limit, hlf of the detection limit (.1 mg nitrte/l) is used for clcultions. 211

214 Percentge of smpling points A sttisticl nlysis ws conducted by mens of n ANOVA (p.5) of the log-trnsformed dt. No sttisticl nlysis ws conducted for ll crops, since no derogtion crops re present in this dtset nd therefore the compred groups re not homogeneous. There is no significnt effect of derogtion on nitrte in the monitoring points (Tble 56). From Tble 56 cn be seen tht lrge number of wter smples hve nitrte concentrtion below the detection limit. The percentges of smpling points in specific rnge of nitrte concentrtion re given for derogtion nd no derogtion prcels seprtely in Figure 194 to Figure 197. For prcels cultivted with ll crops nd on ll soil textures, 82 % of smpling points linked to derogtion prcels nd 77 % of smpling points linked to no derogtion prcels hve nitrte concentrtion below 5 mg/l (Figure 194) D: 82% ND: 77% 3 2 Derogtion No derogtion 1 < >1 Nitrte (mg/l) Figure 194: Percentge of smpling points in specific rnge of nitrte (mg/l) linked to the prcels of 211 for ll crops, bsed on the trvel time. The red verticl line indictes the qulity threshold of 5 mg/l. For prcels cultivted with derogtion crops on ll soil textures, 82 % of smpling points linked to derogtion prcels hve nitrte concentrtion below 5 mg/l while 78 % of smpling points linked to no derogtion prcels hve nitrte concentrtion below 5 mg/l (Figure 195). 212

215 Percentge of smpling points D: 82% ND: 78% 3 2 Derogtion No derogtion 1 < >1 Nitrte (mg/l) Figure 195: Percentge of smpling points in specific rnge of nitrte (mg/l) linked to the prcels of 211 for derogtion crops, bsed on the trvel time. The red verticl line indictes the qulity threshold of 5 mg/l. For derogtion nd no derogtion prcels cultivted with grss on ll soil textures, respectively 88 nd 87 % of smpling points linked to the prcels hve nitrte concentrtion below 5 mg/l (Figure 196). For prcels cultivted with mize on ll soil textures, 74 % of smpling points linked to derogtion prcels hve nitrte concentrtion below 5 mg/l nd 7 % of smpling points linked to no derogtion prcels hve nitrte concentrtion below 5 mg/l (Figure 197). A lrge vrition exists between the smpling points nd in some of the smpling points (linked to both derogtion nd no derogtion prcels) very high concentrtions (> 1 mg/l) re mesured. 213

216 Percentge of smpling points Percentge of smpling points D: 88% ND: 87% 3 2 Derogtion No derogtion 1 < >1 Nitrte (mg/l) Figure 196: Percentge of smpling points in specific rnge of nitrte (mg/l) linked to the prcels of 211 cultivted with grss, bsed on the trvel time. The red verticl line indictes the qulity threshold of 5 mg/l D: 74% ND: 7% 3 2 Derogtion No derogtion 1 < >1 Nitrte (mg/l) Figure 197: Percentge of smpling points in specific rnge of nitrte (mg/l) linked to the prcels of 211 cultivted with mize, bsed on the trvel time. The red verticl line indictes the qulity threshold of 5 mg/l. 214

217 Tble 57 shows the nitrte residue in 211 nd the nitrte concentrtion in groundwter linked to the prcel chrcteristics of 211 bsed on the trvel time. As mentioned before it is very importnt to notice tht the nitrte concentrtion in the groundwter is not only influenced by the nitrte residue. Other prmeters tht influence the effect of the nitrte residue on the nitrte concentrtion in the groundwter re the concentrtion of nitrte in the profile t -9 cm nd the process fctor s discussed in prgrph 14. Tble 57: Averge nitrte residue in 211 (kg N/h) nd verge nitrte concentrtion in groundwter (mg NO 3/l) of monitoring points linked (bsed on the trvel time) to the prcel chrcteristics of 211. Derogtion No derogtion Nitrte residue (kg N/h) Nitrte (mg/l) Nitrte residue (kg N/h) Nitrte (mg/l) verge (min, mx) verge (min, mx) verge (min, mx) verge (min, mx) All crops 87 (5, 54) 26 (dl, 18) 1 (8, 48) 22 (dl, 19) Derogtion crops 87 (5, 54) 26 (dl, 18) 86 (8, 341) 2 (dl, 19) Grss 63 (5, 176) 18 (dl, 131) 48 (8, 112) 1 (dl, 69) Mize 123 (21, 54) 38 (dl, 18) 114 (15, 341) 27 (dl, 19) For derogtion crops, nd more specificlly for grss nd mize, no significnt difference between derogtion nd no derogtion were found, neither in nitrte residue (see prgrph 6.1) nor in nitrte mesured in the wter (Tble 56) Prcel chrcteristics of 212 Bsed on the trvel time, wter smples from utumn of 212, utumn nd spring of 213 nd 214 were linked to the prcel chrcteristics of 212. This comprison is not complete for severl resons. To complete this dtset wter smples should be tken until spring 215 regrding the trvel time. At the monitoring wells no wter smples will be tken in spring 215. For the MAP smpling points only the mesurements until utumn 213 re published nd mesurements of spring nd utumn 214 re not vilble yet. A sttisticl nlysis ws conducted by mens of n ANOVA (p.5) of the log-trnsformed dt. No sttisticl nlysis ws conducted for ll crops, since no derogtion crops re present in this dtset nd therefore the compred groups re not homogeneous. 215

218 Percentge of smpling points Tble 58: Averge nitrte (mg/l) of monitoring points linked (bsed on the trvel time) to the prcel chrcteristics of 212. The number of prcels is indicted by n. A one-wy ANOVA (p.5) ws crried out between derogtion nd no derogtion prcels bsed on the log-trnsformed dt. Nitrte (mg/l) Derogtion No derogtion n verge (min, mx) <dl n verge (min, mx) <dl p-vlue All crops (dl, 139) (dl, 237) 1 - Derogtion crops (dl, 139) (dl, 124) 1.36 Grss (dl, 132) (dl, 93) 5.66 Mize (dl, 139) (dl, 79) 4.81 dl: detection limit (.2 mg/l nitrte for groundwter). For the smples below detection limit, hlf of the detection limit (.1 mg nitrte/l) is used for clcultions. There is no significnt effect of derogtion in 212 on nitrte in the monitoring points (Tble 58), nor when grss (p =.66) nor when mize (p =.81) ws cultivted. The percentges of smpling points in specific rnge of nitrte concentrtion re given for derogtion nd no derogtion prcels seprtely in Figure 198 to Figure 21. For prcels cultivted with ll crops nd on ll soil textures, 83 % of smpling points linked to derogtion prcels nd 86 % of smpling points linked to no derogtion prcels hve nitrte concentrtion below 5 mg/l (Figure 198) D: 83% ND: 86% 3 2 Derogtion No derogtion 1 < >1 Nitrte (mg/l) Figure 198: Percentge of smpling points in specific rnge of nitrte (mg/l) linked to the prcels of 212 for ll crops, bsed on the trvel time. The red verticl line indictes the qulity threshold of 5 mg/l. 216

219 Percentge of smpling points For prcels cultivted with derogtion crops on ll soil textures, 83 % of smpling points linked to derogtion prcels hve nitrte concentrtion below 5 mg/l nd 9 % of smpling points linked to no derogtion prcels hve nitrte concentrtion below 5 mg/l (Figure 199) D: 83% ND: 9% 3 2 Derogtion No derogtion 1 < >1 Nitrte (mg/l) Figure 199: Percentge of smpling points in specific rnge of nitrte (mg/l) linked to the prcels of 212 for derogtion crops, bsed on the trvel time. The red verticl line indictes the qulity threshold of 5 mg/l. For derogtion nd no derogtion prcels cultivted with grss on ll soil textures, respectively 88 nd 89 % of smpling points linked to the prcels hve nitrte concentrtion below 5 mg/l (Figure 2). For prcels cultivted with mize on ll soil textures, 75 % of smpling points linked to derogtion prcels hve nitrte concentrtion below 5 mg/l nd 94 % of smpling points linked to no derogtion prcels hve nitrte concentrtion below 5 mg/l (Figure 21). A lrge vrition exists between the smpling points nd in some of the smpling points (linked to both derogtion nd no derogtion prcels) very high concentrtions (> 1 mg/l) re mesured. 217

220 Percentge of smpling points Percentge of smpling points D: 88% ND: 89% 3 2 Derogtion No derogtion 1 < >1 Nitrte (mg/l) Figure 2: Percentge of smpling points in specific rnge of nitrte (mg/l) linked to the prcels of 212 cultivted with grss, bsed on the trvel time. The red verticl line indictes the qulity threshold of 5 mg/l D: 75% ND: 94% 3 2 Derogtion No derogtion 1 < >1 Nitrte (mg/l) Figure 21: Percentge of smpling points in specific rnge of nitrte (mg/l) linked to the prcels of 212 cultivted with mize, bsed on the trvel time. The red verticl line indictes the qulity threshold of 5 mg/l. 218

221 7.2.5 Prcel chrcteristics of 213 Bsed on the trvel time, wter smples from utumn of 213, utumn nd spring of 214 were linked to the prcel chrcteristics of 213. Tble 59: Averge nitrte (mg/l) of monitoring points linked (bsed on the trvel time) to the prcel chrcteristics of 213. The number of prcels is indicted by n. Nitrte (mg/l) Derogtion No derogtion n verge (min, mx) <dl n verge (min, mx) <dl p-vlue All crops (dl, 141) (dl, 111) - Derogtion crops (dl, 141) (dl, 111) - Grss 9 13 (dl, 59) (dl, 111) - Mize 9 26 (dl, 141) dl: detection limit (.2 mg/l nitrte for groundwter). For the smples below detection limit, hlf of the detection limit (.1 mg nitrte/l) is used for clcultions. Comprison of derogtion nd no derogtion prctices in 213 is t end 214 possible for only 21 prcels. For some prcels the necessry mesurements of MAP smpling points re not vilble yet nd other prcels hve longer trvel time. Since the prcels re selected in such wy tht trvel time is limited, evlution of the effect of derogtion nd no derogtion prctices in 213 on the nitrte content in shllow groundwter, cn be finished when mesurements until spring 216 will be finished nd vilble. Since the comprison in function of the prcel chrcteristics of 213 is bsed on smll number of prcels, no grphs re mde nd no sttisticl nlysis is conducted. 219

222 7.3 Nitrte in the soil wter On selected prcels soil smple from 9 to 12 cm is tken in spring nd utumn. Most of these prcels hve low groundwter level. As consequence the wter smples from MAP smpling points groundwter or monitoring wells linked to these prcels hve long trvel times. The nitrte mesured in the deeper soil lyers is n indiction of the mount of nitrte in the wter of tht specific prcel. By tking into ccount the moisture content of the soil, the mount of nitrte mesured in the soil profile is reclculted to nitrte concentrtion in the wter. In Tble 6, the verge vlue for the nitrte (mg/l) concentrtion in the soil wter is shown. A sttisticl nlysis ws conducted by mens of n ANOVA (p.5) of the log-trnsformed dt. No sttisticl nlysis ws conducted for ll crops, since no derogtion crops re present in this dtset nd therefore the compred groups re not homogeneous. In utumn 211, there is no significnt difference in nitrte concentrtion between derogtion nd no derogtion prcels cultivted with derogtion crops nd grss. However, mize prcels under derogtion hve sttisticlly higher nitrte concentrtion thn no derogtion prcels. Since spring 212 until spring 214 there is no significnt difference in nitrte concentrtion between derogtion nd no derogtion prcels not for derogtion crops, nor for prcels cultivted with grss or mize. 22

223 Tble 6: Averge vlue for the nitrte (mg/l) concentrtion mesured nd reclculted in the deep soil lyer (9-12 cm) for the different moments of smpling. Distinction is mde between derogtion nd no derogtion prcels. The number of prcels is indicted by n. A one-wy ANOVA (p.5) ws crried out between derogtion nd no derogtion prcels bsed on the log-trnsformed dt. Nitrte (mg/l) in the soil wter Dte No n Derogtion (min, mx) n (min, mx) p-vlue derogtion Autumn 211 All crops (3, 32) (9, 343) - Derogtion crops (3, 34) 2 68 (9, 224).71 Grss 9 52 (3, 122) 9 47 (9, 87).83 Mize (6, 33) (38, 224).3 Spring 212 All crops 1 61 (1, 24) (9, 281) - Derogtion crops 1 61 (1, 24) (9, 281).52 Grss 7 34 (1, 115) 1 88 (9, 281).7 Mize (62, 24) (39, 24).9 Autumn 212 All crops (6, 395) (12, 282) - Derogtion crops (6, 395) (12, 148).33 Grss 9 9 (31, 395) 7 42 (12, 148).1 Mize 4 71 (6, 21) 8 52 (13, 69).57 Spring 213 All crops (13, 147) (13, 368) - Derogtion crops (13, 147) (13, 215).57 Grss 8 58 (13, 147) 4 46 (13, 126).48 Mize 4 36 (23, 68) 8 76 (32, 215).9 Autumn 213 All crops (12, 118) 2 5 (5, 198) - Derogtion crops (12, 118) (5, 198).16 Grss 9 51 (12, 83) 8 36 (5, 18).15 Mize 4 6 (29, 118) 8 64 (6, 198).62 Spring 214 All crops 9 38 (6, 119) 16 5 (7, 154) - Derogtion crops 9 38 (6, 119) 13 5 (7, 154).31 Grss 5 44 (6, 119) 5 5 (7, 116).68 Mize 4 32 (7, 51) 7 54 (14, 154).34 Autumn 214 All crops (9, 318) (7, 328) - Derogtion crops (9, 318) (7, 328).5 Grss (9, 318) (7, 52).1 Mize 3 86 (46, 162) (14, 328).92 In utumn 214 sttisticl significnt difference is found between derogtion nd no derogtion prcels for derogtion crops nd for grss prcels. However the rnge of nitrte concentrtion in soil wter ws for both derogtion nd no derogtion prcels lrge (Figure 22 nd Figure 23), 221

224 s experienced t erlier smpling moments. However the results of utumn 214 need to be pproched with the necessry precutions since the nitrte concentrtion in the soil wter ws clerly influenced by the moisture content of the soil. This ws not experienced t erlier smpling moments (Figure 24). 3, Derogtion crops 2,8 2,6 2,4 2,2 log(nitrte soilwter ) 2, 1,8 1,6 1,4 1,2 1,,8,6,4 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 22: Box plot of log(nitrte soil wter) for derogtion nd no derogtion prcels cultivted with derogtion crops on ll soil textures in utumn 214. SE: stndrd error of the men. SD: stndrd devition. 3, Grss 2,8 Mize 2,8 2,6 2,4 2,6 2,4 2,2 2,2 log(nitrte soilwter ) 2, 1,8 1,6 1,4 log(nitrte soilwter ) 2, 1,8 1,6 1,2 1,4 1,,8,6,4 Derogtion J No derogtion N Men Men±SE Men±2*SD 1,2 1,,8 Derogtion J No derogtion N Men Men±SE Men±2*SD Figure 23: Box plot of log(nitrte soil wter) for derogtion nd no derogtion prcels cultivted with grss (left) nd mize (right) on ll soil textures in utumn 214. SE: stndrd error of the men. SD: stndrd devition. 222

225 4 Nitrte in the soilwter versus dry mtter content of soil in spring 212 R²=.1; p=.59 4 Nitrte in the soilwter versus dry mtter content of soil in utum 214 R²=.1149; p= Nitrte soilwter (mg/l) Nitrte soilwter (mg/l) Dry mtter content soil lyer 9-12 cm (%) Dry mtter content soil lyer 9-12 cm (%) Figure 24: Sctterplot of the nitrte concentrtion in the soilwter (mg/l) versus the dry mtter content (%) of the soil lyer 9-12 cm in spring 212 (left) nd utumn 214 (right). 7.4 Cse studies For sttisticl nlysis outliers re removed s indicted before. Some outliers, however, cn be explined nd re the logicl consequence of n event. These outliers provide lot of useful informtion. Tble 61 shows n overview of 4 prcel conversions of grss in 211. On prcel 1 in Mrch 211, before the mize ws sown, the mount of nitrte in the soil (-9 cm) ws 54 kg NO 3 -N/h. When the grsslnd ws ploughed, the grss strted to minerlize. This results in high nitrte residue in October 211 (54 kg NO 3 -N/h). Since this prcel hs trvel time of nitrte from the prcel soil to the monitoring well of lmost 2 yers, the results of this crop chnge cn be mesured in soil wter in utumn 212. The concentrtion of nitrte in the soil wter ws 1.7 mg NO 3 /l, slightly higher s t the smpling moments before. But t the sme level s in utumn 29 nd the concentrtion in the soil wter diminished t lter smpling moments. In 211, less fertiliser ws pplied due to the conversion from grsslnd into mize. The sme cn be seen for prcels 2 nd 3: in 211 the grsslnd is converted into mize nd in October the nitrte residue is high (prcel 2: 232 kg NO 3 -N/h; prcel 3: 341 kg NO 3 -N/h). Fertilistion in 211 ws lower for mize thn for grss the yers before. The high nitrte residue in utumn 211 ws cler signl for the frmers to reduce fertilistion gin. On both prcels less thn 1 kg N/h ws pplied. The effect of grss conversion in spring 211 cn be mesured in soil wter in utumn 212 for prcel 2 nd in utumn 213 for prcel 3. For prcel 2 no increse of nitrte concentrtion in the groundwter, relted to trvel time, is seen fter conversion of grss. For prcel 3 the conversion of grss in spring 211 resulted in higher 223

226 nitrte concentrtion in the groundwter in utumn 213. The nitrte concentrtion reched 58 mg NO 3 /l. At former smpling moments the nitrte concentrtion rnged between 21 nd 39 mg NO 3 /l. For prcel 4 trvel time is shorter. As on the previous prcels, the nitrte residue in utumn 211 is high due to conversion of grsslnd. The nitrte concentrtion in the groundwter linked to the griculturl prctices of 211 nd 212 incresed. The nitrte concentrtion reched 82 mg NO 3 /l in spring 212 nd ws even higher in utumn 212. The nitrte concentrtion t this monitoring well stys t higher level until utumn 214. Conversion of grsslnd into croplnd cn cuse risk for wter qulity. For some prcels there s no impct or rther smll impct on nitrte concentrtion in groundwter. 224

227 Tble 61: Overview of 4 prcels with conversion of grss in 211. The cultivted crop, fertilistion, NO 3 in the ground wter linked to the prcel ccording to trvel time, NO 3 in the ground wter not bsed on the trvel time nd NO 3-N in the soil (-9 cm) is shown for October 29 to 214. (n..= not vilble) Prcel 1 (sndy soil) Oct Spring Oct 21 Spring Oct 211 Spring Oct 212 Spring Oct 213 Spring Oct 214 Derogtion (Yes/No) Y Y Y Y Y Y Crop Grss Grss Mize + grss Mize + grss Mize + grss Mize + grss Fertilistion (kg N/h) n.. NO 3 -N (kg/h) soil NO 3 (mg/l) not linked n..* n.. NO 3 (mg/l) linked Prcel 2 (sndy soil) Oct Spring Oct 21 Spring Oct 211 Spring Oct 212 Spring Oct 213 Spring Oct 214 Derogtion (Yes/No) N N N N N N Crop Grss Grss Mize Mize Pottoes Mize Fertilistion (kg N/h) n.. 69 NO 3 -N (kg/h) soil NO 3 (mg/l) not linked n.. n.. NO 3 (mg/l) linked Prcel 3 (sndy soil) Oct Spring Oct 21 Spring Oct 211 Spring Oct 212 Spring Oct 213 Spring Oct 214 Derogtion (Yes/No) 29 Y 1 Y N N 212 N N Crop Grss Grss Mize Mize Mize Mize Fertilistion (kg N/h) n.. NO 3 -N (kg/h) soil NO 3 (mg/l) not linked n.. n.. NO 3 (mg/l) linked Prcel 4 (sndy soil) Oct Spring Oct 21 Spring Oct 211 Spring Oct 212 Spring Oct 213 Spring Oct 214 Derogtion (Yes/No) 29 Y 1 Y Y Y 212 Y N Crop Grss Grss Mize + grss Mize + grss Mize + grss Mize + grss Fertilistion (kg N/h) n.. NO 3 -N (kg/h) soil NO 3 (mg/l) not linked NO 3 (mg/l) linked

228 7.5 Conclusion The nitrte concentrtion in drins linked to derogtion prcels ws in spring 213 nd 214 lower thn in utumn 212 nd 213, while the nitrte concentrtion in drins linked to no derogtion prcels ws higher in spring 213 nd 214 thn in utumn 212 nd 213. No sttisticl nlysis ws conducted since only smll number of drins re vilble nd the mesurement of cnls nd ditches my be influenced by other prmeters. MAP smpling points groundwter nd monitoring wells were linked to single griculturl prcel bsed on the trvel time nd infiltrtion re nd the prcel chrcteristics of 29, 21, 211 nd 212. There is mostly no sttisticlly significnt difference (p.5) in nitrte concentrtion in MAP monitoring points groundwter nd monitoring wells of derogtion nd no derogtion prcels with derogtion crops, grss or mize. Only in 21 derogtion crops nd mize on no derogtion prcels resulted in higher nitrte concentrtions in the groundwter. The nitrte content in the deeper soil lyer (9-12) cm ws clculted to nitrte concentrtion in the soil wter. There is no sttisticl difference in utumn 211, 212 nd 213, nd spring 212, 213 nd 214, between derogtion nd no derogtion prcels with derogtion crops for nitrte in the soil wter. However, for prcels cultivted with mize in utumn 211, derogtion prcels hve sttisticlly higher nitrte concentrtion in the soil wter thn no derogtion prcels. There is no sttisticl difference in spring 212, utumn 212, spring 213, utumn 213 nd spring 214 between derogtion nd no derogtion prcels for nitrte in the soil wter for prcels cultivted with derogtion crops nd grss. In utumn 214 derogtion prcels hve sttisticlly higher nitrte concentrtion in the soil wter thn no derogtion prcels when cultivted with grss. 8 Phosphorus in the soil profile 8.1 P-AL in the stndrd soil smple On ll prcels of the derogtion monitoring network stndrd soil smple ws tken. On this stndrd soil smple different prmeters were nlysed (soil texture, ph, C, P, K, Mg, C, N). Bsed on the stndrd soil smple fertilistion dvice ws formulted for ech prcel for the next 3 yers. In Tble 62 only 186 of the 217 prcels re shown. This is due to the fct tht some prcels were lredy fertilized when the soil smple ws tken nd sttisticl outliers were removed. Eight sttisticl outliers were removed: 4 from derogtion prcels (68 mg P/1 g dry 226

229 soil, 66 mg P/1 g dry soil, 61 mg P/1 g dry soil nd 61 mg P/1 g dry soil) nd 4 from no derogtion prcels (58 mg P/1 g dry soil, 6 mg P/1 g dry soil, 6 mg P/1 g dry soil nd 4 mg P/1 g dry soil). From the high sttisticl outliers (68, 66, 61, 61 nd 58 mg P/1g dry soil) 4 prcels exceeded the mximl limits of fertilized P 2 O 5. On these prcels, 15, 135, 131 nd 1 kg P 2 O 5 /h/yer ws pplied in 211. Two prcels were cultivted with grss nd were grzed; one prcel ws cultivted with mize nd one with spinch. Since stndrd soil smple is tken from to 6 cm for grsslnd nd from to 23 cm for mize nd other crops, sttisticl nlysis ws only crried out for these crops seprtely. Phosphorus on the stndrd soil smple is mesured in n mmonium-lctte (AL) extrct. Tble 62: Averge phosphorus (mg/1 g dry soil, in mmonium-lctte extrct) mesured in the soil lyer from -6 cm for grss nd -23 cm for other crops in spring 212. Distinction is mde between derogtion nd no derogtion prcels. The number of prcels is indicted by n. A one-wy ANOVA (p.5) ws crried out between derogtion nd no derogtion prcels bsed on the log-trnsformed dt. P-AL (mg/1g dry soil) n Derogtion (min, mx) n No derogtion (min, mx) p-vlue All crops (8, 52) (8, 56) - Derogtion crops (8, 52) (8, 51) - Grss 42 3 (8, 52) (8, 51).36 Mize 24 3 (12, 47) (13, 55).16 Bsed on the soil fertility clsses, s estblished by SSB (Mes et l., 212), the plnt vilble phosphorus on the prcels of the derogtion monitoring network is reltively high for grss prcels (3 mg P/1 g dry soil), wheres for rble lnd it is considered high (3-34 mg P/1 g dry soil). However, it is not uncommon in Belgium to hve high P-AL in the soil: 77 % of the prcels with rble lnd nd 56% of the grss prcels in Belgium hve P-AL bove the optiml level (Mes et l., 212). Comprison of the verge P-AL in the soil profile in 29 (Vndervelpen et l., 211) nd the verge P-AL for grss nd mize prcels in 212 shows tht P-AL ws rther the sme t both moments. The mount of phosphorus ws still in the sme order of mgnitude. In Figure 25 the percentge of derogtion nd no derogtion prcels is shown for different P- AL soil fertility clsses for both derogtion nd no derogtion prcels. Most of the derogtion nd no derogtion prcels re clssified s rther high for the prmeter P-AL. 227

230 % of smples Derogtion No derogtion Figure 25: Percentge of derogtion nd no derogtion smples in different soil fertility clsses for the prmeter P-AL (mg/1g dry soil) in spring P-AL in the stndrd soil smple, prcels which were continuously under derogtion/no derogtion during In order to verify the long-term impct of derogtion on the P-AL in the soil, only prcels tht were continuously under derogtion/no derogtion during were retined. Tble 63 shows the verge vlues for the soil phosphorus of derogtion nd no derogtion prcels nd for different crops in spring 212. For ll soil fertility prmeters, seven soil fertility clsses (rnging from very low to very high) re estblished depending on soil texture nd orgnic mtter content of the soil (Mes et l., 212). These soil fertility clsses re different for grsslnd nd rble lnd. The middle clss is the optiml level. Within this level most plnts show n optiml growth if rtionl fertilistion nd liming re pplied. For grss prcels, 27 nd 3 mg P/1 g dry soil is reltively high, wheres for rble lnd 34 nd 37 mg P/1 g dry soil is high. Since stndrd soil smple is tken from to 6 cm for grsslnd nd from to 23 cm for mize nd other crops, sttisticl nlysis ws only crried out for these crops seprtely. 228

231 Tble 63: Averge phosphorus (mg/1 g dry soil, in mmonium-lctte extrct) mesured in the soil lyer from -6 cm for grss nd -23 cm for other crops in spring 212, only for prcels which were under derogtion/no derogtion during Distinction is mde between derogtion nd no derogtion prcels. The number of prcels is indicted by n. A one-wy ANOVA (p.5) ws crried out between derogtion nd no derogtion prcels bsed on the log-trnsformed dt. P-AL (mg/1g dry soil) n Derogtion (min, mx) n No derogtion (min, mx) p-vlue All crops (8, 52) (8, 56) - Derogtion crops (8, 52) (8, 55) - Grss (8, 51) 28 3 (8, 51).65 Mize (12, 52) (11, 55) P-AL in the deep soil smples (9-12 cm) In ll deep soil smples (from 9 to 12 cm) the mount of phosphorus is lso mesured in n mmonium-lctte extrct. Yer fter yer reltive high number of smples hd n mount of phosphorus below detection limit, rnging from 47 % in utumn 212 to 67 % in utumn 213. Although lrge proportion of the phosphorus mesurements were below detection limit, prcels with very high mounts of phosphorus were observed t every time of smpling. Further interprettion of these dt when considered s outliers, is given below. In utumn 211 the mesured phosphorus is high in 6 prcels (>1 mg P/1 g dry soil). In spring 212, the mesured phosphorus is higher thn 1 mg P/1 g dry soil in 7 prcels. Among these prcels with high phosphorus in the soil lyer from 9-12 cm, there re both derogtion nd no derogtion prcels present (Tble 64). For spring 212, two sttisticl outliers were removed: 47 mg P/1 g dry soil for derogtion prcel cultivted with grss nd 39 mg P/1 g dry soil for no derogtion prcel cultivted with spinch. For utumn 212, two sttisticl outliers were removed (31 nd 29 mg P/1 g dry soil for one derogtion nd one no derogtion prcel). For spring 213, 2 sttisticl outliers were removed, prcels cultivted with mize with derogtion (18 mg P/1 g dry soil) nd without derogtion (15 mg P/1 g dry soil). For utumn 213, three sttisticl outliers were removed (16, 14 nd 13 mg P/1 g dry soil) for mize prcel without derogtion on cly soil nd prcels without derogtion on sndy soil cultivted with winter whet nd grss. However the mount of phosphorus in the soil lyer 9-12 cm ws below detection limit in 61 % of deep soil smples. In spring 214 in 46 % of the smples the mount of phosphorus is below the detection limit of 4 mg P/1 g dry soil. Three 229

232 outliers were detected. Two prcels with derogtion on sndy soil with grss (17 mg P/1 g dry soil) nd mize (15 mg P/1 g dry soil). One prcel on sndy lom soil cultivted with cbbge in 213. In utumn outlier ws detected for the mount of phosphorus in the soil lyer from 9 to 12 cm. The grss prcel on sndy soil cultivted without derogtion showed hd n mount of 14 mg P/1 g dry soil in the deep soil lyer. The mount of phosphorus in the deep soil lyer (9-12 cm) is mostly influenced by fertilistion history nd long term culture prctices. Therefore n explntion of the outliers is not lwys possible. However some prcels re detected s sttisticl outlier t severl smpling moments. Even though it needs to be noticed tht the vlues detected s sttisticl outlier diminished. High vlues of 47 nd 39 mg P/1 g dry soil re no longer noticed since spring 213. The verge phosphorus level in the deep soil lyer ws similr on derogtion nd no derogtion prcels. Only in utumn 211, utumn 212 nd spring 213 some lrger difference (> 1 mg P/ 1 g dry soil) ws seen. However, becuse of the lrge number of smples below detection limit, no sttisticl nlysis is conducted. Tble 64: Averge phosphorus (mg/1 g dry soil, in mmonium-lctte extrct) for the soil lyer 9-12 cm for derogtion nd no derogtion prcels. The number of prcels is indicted by n. Derogtion No derogtion n verge (min, mx) <dl n verge (min, mx) <dl Autumn (dl, 27) (dl, 15) 15 Spring (dl, 15) (dl, 15) 8 Autumn (dl, 2) (dl, 19) 11 Spring (dl, 8) (dl, 13) 6 Autumn (dl, 11) (dl, 18) 13 Spring (dl, 11) (dl, 13) 1 Autumn (dl, 9) (dl,1) 13 For the smples below the detection limit (4 mg/1 g dm), hlf of the detection limit (2 mg/1 g dm) is used for the clcultions. 8.4 Phosphte sturtion degree High concentrtions of phosphorus in the surfce- nd groundwter re not desirble, since it my result in eutrophiction. The generl eutrophiction limit of orthophosphte is.1 mg P/l (Schouwmns, 24). Soils hve certin sorption cpcity: when phosphorus is dded to the soil, ( prt of) the totl phosphte sorption cpcity is occupied. In this wy, the phosphte 23

233 sorption cpcity decreses nd eventully phosphorus will lech out. The mount of phosphte leching out is function of the totl phosphorus in the soil, the soil binding cpcity nd the hydrologicl chrcteristics of the soil. A good mngement of phosphorus in the soil is necessry in order to prevent risks of phosphorus leching. Vn der Zee et l. (199, b) developed protocol for cid sndy soils to test whether soil is phosphte sturted. In cid sndy soils, phosphte is mostly bsorbed by iron nd luminium oxides nd hydroxides. When soils re clcreous, phosphorus will form insoluble complexes with clcium. In tht cse not only the mount of iron nd luminium is of importnce to clculte the phosphte sorption cpcity (PSC). By n mmonium oxlte extrction the phosphorus bsorbed on luminium nd iron oxides nd hydroxides is mesured nd the PSC cn be clculted. Besides iron nd luminium lso the oxlte extrctble P is mesured. Vn der Zee quntified the reltion between PSC nd Pox (oxlte extrctble phosphorus) s the Phosphte Sturtion Degree (PSD). The phosphte sturtion degree (PSD) cn be expressed s: PSD = (1 * P ox )/PSC With PSC: Phosphte sorption cpcity:.5 * (Al ox +Fe ox ) Tble 65 shows the results of the phosphte sturtion degree mesured in 3 prcels of the monitoring network. All prcels re chrcterized by sndy soil type nd re mostly cid, so tht the model of Vn der Zee cn be used in order to clculte the phosphte sturtion degree. More thn hlf of the tested prcels re phosphte sturted (PSD > 35 %, s declred in Flemish legisltion). This mens tht on these prcels phosphte my lech out of the soil profile to the surfce- nd groundwter. The phosphte sturted prcels re both derogtion nd no derogtion prcels nd re both cultivted with grss nd mize. Due to the low number of tested prcels, no sttisticl comprison ws mde between derogtion nd no derogtion prcels. 231

234 Tble 65: Phosphte sturtion degree mesured on selection of 3 prcels on sndy soils of the monitoring network t the end of 212. The results for oxlte extrctble phosphorus (Pox), oxlte extrctble luminium (Al ox), oxlte extrctble iron (Fe ox), Phosphte Sorption Cpcity (PSC), Phosphte Sturtion Degree (PSD) nd the number of phosphte sturted prcels conform Flemish legisltion re shown. Crop 212 n P ox (mmol/kg) Al ox (mmol/kg) Fe ox (mmol/kg) PSC (mmol P/kg) PSD (%) Nr P-sturted prcels-conform Flemish legisltion Derogtion Grss Mize No derogtion Grss Mize Conclusion The verge P-AL (mg/1g dry soil) is 31 nd 33 mg P/1g dry soil in derogtion prcels nd no derogtion prcels respectively. There is no significnt difference in P-AL in grss prcels under derogtion or no derogtion. There is lso no significnt difference in P-AL in mize prcels under derogtion or no derogtion. For prcels continuously under derogtion or no derogtion during , the verge P-AL of derogtion or no derogtion prcels did not differ sttisticlly, nor for grss prcels nor for mize prcels. In the deeper soil lyer (9-12 cm), vrible concentrtions of P-AL re found t ll moments of smpling, from utumn 211 till utumn 214. A lrge prt of the dt for the deep soil smple is under detection limit. Therefore no sttisticl nlysis is conducted. More thn hlf of the selected grss nd mize prcels cultivted on sndy soils re phosphte sturted ccording to the Flemish legisltion where phosphte sturted prcels re defined s prcels with PSD higher thn 35 %. Since no protocol exists yet to clculte the phosphte sturtion degree on other soil types, it is not possible to investigte this prmeter in detil. 232

235 9 Phosphorus in the surfce nd groundwter 9.1 Drins, cnls, ditches nd smpling points In ll wter smples (from cnls, ditches, drins, MAP smpling points groundwter nd monitoring wells) of the monitoring network the mount of phosphorus is mesured by using continuous flow system. The results re summrized in Tble 66 nd Tble 67. Since dt for MAP smpling points for spring nd utumn 214 re not vilble yet, these dt re not represented in the tble. These smples could give n indiction of the wter qulity. However, the link between the smpling point for the surfce wter nd prticulr prcel of the monitoring network is not lwys very cler. Therefore the concentrtions of phosphorus in the wter smples of drins, cnls nd ditches re rther indictive. During the different yers, the highest concentrtion of phosphorus is mesured in drins, cnls nd ditches. The lowest concentrtions re mesured in the monitoring wells, representing shllow groundwter. However no decresing trend ws observed for For cnls nd ditches in November 211, two sttisticl outliers (9.17 nd 4.7 mg P/l) were removed. The first prcel is long term grss prcel for which the mount of P-AL in the soil lyer -6 cm ws 31 mg P-AL/1 g dry soil in spring 212. On the second prcel lso deep soil smples were tken. In the soil lyer 9-12 cm in utumn 211 the mount of P-AL mesured ws 27 mg P-AL/ 1 g dry soil, the highest vlue mesured in the deep soil smples t tht moment. For the monitoring wells, one sttisticl outlier is removed (3.87 mg P/l) nd for the MAP smpling points groundwter, two sttisticl outliers were removed s well (3. nd 3. mg P/l). For Februry 212, one sttisticl outlier (3.41 mg P/l) ws removed for the monitoring wells. For cnls nd ditches in November 212, three sttisticl outliers were removed (2.73, 2.78 nd 3.51 mg P/l; grss prcels with nd without derogtion). For the drins, one sttisticl outlier ws removed (7.4 mg P/l; grss prcel without derogtion). For the monitoring wells, one sttisticl outlier ws removed (3.44 mg P/l; grss prcel with derogtion). For the MAP smpling points one sttisticl outlier ws removed (3.1 mg P/l). In spring 213, two sttisticl outliers were removed: 8.5 (drin), 3.4 (monitoring well) mg P/l. For the MAP smpling points groundwter, three sttisticl outliers were removed (1.23, 1.35 nd 1.97 mg P/l). On 62 out of the 97 smpled 233

236 MAP smpling points groundwter the orthophosphte-p concentrtion ws below detection limit. In utumn 213 one outlier ws removed for cnls nd ditches (6.48 mg P/l) nd one outlier for drins (7.82 mg P/l). Also for the monitoring wells two sttisticl outliers were removed (4.3 nd 1.78 mg P/l). The drin nd monitoring well which were outliers in utumn 213, were lso outliers in spring 214 (drin: mg P/l; monitoring well: 4. mg P/l). For the MAP smpling points 2 outliers were removed (1.9 nd 1.3 mg P/l) in utumn 213. These MAP smpling points were lso detected s outliers in spring 213. For 37 of the 9 smpled MAP smpling points groundwter in utumn 213, the orthophosphte-p concentrtion ws below detection limit. Tble 66: Averge vlues for orthophosphte-p (mg P/l) mesured in the different wter smples. Difference is mde between derogtion nd no derogtion prcels. PO 4 -P mg/l Derogtion No derogtion n verge (min, mx) n verge (min, mx) Autumn 211 Drins (1.62, 2.) Cnls, ditches (dl, 2.92) (dl, 2.1) Spring 212 Drins 3.4 (.9,.99) Cnls, ditches (dl,.57) 1.56 (dl, 2.5) Autumn 212 Drins 6.42 (.7, 1.) 5.4 (dl,.88) Cnls, ditches 15.2 (dl,.7) 7.64 (dl, 1.43) Spring 213 Drins 6.29 (dl, 1.7) 5.16 (dl,.4) Cnls, ditches (dl,.68) 9.63 (dl, 1.33) Autumn 213 Drins 3.3 (.7,.75) 1 dl - Cnls, ditches (dl, 2.21) (dl, 1.6) Spring 214 Drins 3.3 (.1,.46) 4.9 (dl,.24) Cnls, ditches (dl, 3.25) 1.38 (dl, 1.56) Autumn 214 Drins (dl, 1.17) Cnls, ditches (dl, 2.5) (dl, 1.66) For the smples below the detection limit (.4 mg/l orthophosphte-p), hlf of the detection limit (.2 mg/l orthophosphte-p) is used for the clcultions. 234

237 In utumn outliers were detected t cnls nd ditches, ll t grss prcels. Three prcels were cultivted without derogtion (2.7, 2.83 nd 4.89 mg P/l). The prcel t which 4.89 mg P/l ws mesured t the ditch, showed lso higher P-vlues in the deep soil lyer 9-12 cm in utumn 214. This soil lyer contined 14 mg P-AL/1 g dry soil, detected s the only sttisticl outlier in utumn 214. The fourth prcel detected s outlier t cnls nd ditches, ws cultivted without derogtion (3.3 mg P/l). For the monitoring wells 2 outliers were detected: 2.1 nd 2.28 mg P/l. For some prcels the mounts of orthophosphte-p in the wter smples re regulrly detected s sttisticl outliers. This concerns however both derogtion nd no derogtion prcels. For one prcel with monitoring well, the mount of orthophosphte-p in the groundwter ws detected s sttisticl outlier t every moment of smpling. This prcel ws long term grss prcel on cly soil. The input-output blnce for P ws negtive (output higher thn input). Tble 67: Averge orthophosphte-p concentrtion (mg P/l) in the MAP smpling points (M) nd monitoring wells (W) linked to prcel of the monitoring network for different yers. For ech yer the number of prcels is indicted by n. PO 4 -P (mg/l) n M (min, mx) n W (min, mx) 211_ utumn (dl, 1.8) (dl, 1.84) 212_ spring (dl, 1.75) (dl, 1.5) 212_ utumn 91.1 (dl, 1.32) (dl, 1.48) 213_ spring 97.5 (dl-.45) (dl, 1.3) 213_ utumn 88.8 (dl-.62) (dl, 1.3) 214_ spring (dl, 1.22) 214_utumn (dl, 1.27) For the smples below the detection limit (.4 mg/l orthophosphte-p), hlf of the detection limit (.2 mg/l orthophosphte-p) is used for the clcultions. 9.2 DIP, DOP nd totl P In 5 % of ll wter smples of the derogtion monitoring network the totl mount of phosphorus is mesured by ICP (Inductive Coupled Plsm). The frction of DIP (dissolved inorgnic phosphorus) nd DOP (dissolved orgnic phosphorus) re determined by mesuring the mount of DIP with IC (Ion Chromtogrphy). The mount of DIP is subtrcted from the totl phosphorus, which results in the mount of DOP. By determining the frctions of DIP nd 235

238 DOP from the totl phosphorus mount, it is possible to identify the most importnt frction (DIP or DOP). The results of the mesurements re shown in Tble 68. For both derogtion nd no derogtion prcels, the concentrtion of totl phosphorus in drins is higher thn in cnls, ditches, monitoring wells or centrifuged soil wter (except in Autumn 212 nd spring 213 for derogtion prcels). The concentrtion of totl phosphorus in monitoring wells nd soil wter is the lowest. In monitoring wells, pproximtely 6 % of the mesured totl phosphorus is below detection limit. However, some of the monitoring wells hve very high vlues of totl phosphorus. In spring 213 the mount of DIP ws in lmost ll wter smples below detection limit, s seen in Tble 68. In spring 213 ll wter smples were nlysed for totl mount of phosphorus nd the mount of dissolved inorgnic phosphorus (Tble 69). These results confirm the fct tht the concentrtion of totl phosphorus in drins is often higher thn in cnls, ditches, monitoring wells or soil wter. Like in spring nd utumn 212 nd on the selection of prcels in spring 213, the concentrtion of totl phosphorus in drins ws higher on prcels without derogtion. 236

239 Tble 68: Averge mount of totl phosphorus (TP, mg P/l), DIP (dissolved inorgnic phosphorus, mg P/l)) nd DOP (dissolved orgnic phosphorus, mg P/l) for the different wter smples. For ech combintion the number (n) of smples is given s well s the number of smples with DIP mesurement below detection limit (<dl). Derogtion No derogtion n TP DIP DOP % DIP % DOP < dl n TP DIP DOP % DIP % DOP <dl Autumn 211 Drins Cnls nd ditches Monitoring wells Soil wter (9-12 cm) Spring 212 Drins Cnls nd ditches Monitoring wells Soil wter (9-12 cm) Autumn 212 Drins Cnls nd ditches Monitoring wells Soil wter (9-12 cm) Spring 213 Drins Cnls nd ditches Monitoring wells Soil wter (9-12 cm) for the clcultion of vlues below detection limit, hlf of the detection limit is used. 237

240 Tble 69: Averge mount of totl phosphorus (TP, mg P/l), DIP (dissolved inorgnic phosphorus, mg P/l)) nd DOP (dissolved orgnic phosphorus, mg P/l) for the different wter smples of spring 213. For ech combintion the number (n) of smples is given s well s the number of smples with DIP mesurement below detection limit (<dl). Derogtion No derogtion n TP DIP DOP % DIP % DOP < dl n TP DIP DOP % DIP % DOP <dl Spring 213 Drins Cnls nd ditches Monitoring wells for the clcultion of vlues below detection limit, hlf of the detection limit is used. 238

241 In generl, the totl phosphorus is lower in spring 212 compred to utumn 211. This is due to the fct tht the mount of DIP decreses, while the concentrtion of DOP remins constnt over time. The totl phosphorus concentrtion in utumn 212 is comprble to the totl phosphorus in spring 212. The totl P mesured in the wter smples is highly vrible both under derogtion nd no derogtion conditions. This is illustrted in box plot in Figure 26 for the mesurements in the monitoring wells in Autumn 211. Sme vrition is observed for other mesurements (drins, cnls, ditches nd soil wter). log(totl P) Totl P of monitoring wells in utumn 211 Derogtion J No N derogtion Vr1 Men Men±SE Men±2*SD Figure 26: Box plot of log(totl phosphorus (mg P/l)) mesured with CF for the monitoring wells in utumn 211. SE: stndrd error of the men. SD: stndrd devition. In chpter 9.1 the mount of phosphorus is mesured with the continuous flow (CF) system. CF gives n indiction of the mount of DIP in the wter smples. CF is bsed on colour rection with the inorgnic phosphorus frction, but lso prt of the orgnic frction of phosphorus. Theoreticlly, phosphorus mesurements with CF should be slightly higher thn DIP mesurements with IC (Tble 7). As seen in the tble, the phosphorus mesurements with CF re higher thn DIP mesurements with IC, except for cnls nd ditches in utumn 211 nd 212. Since in spring 213 the mount of DIP ws in lmost ll of the smples below detection limit, the verge vlues of DIP re very low. 239

242 Tble 7: Averge vlue of DIP (mg P/l) nd PO 4-P (mg P/l) for prcels where DIP ws mesured. n DIP (IC) PO 4 -P (CF) Autumn 211 Drins Cnls nd ditches Monitoring wells Spring 212 Drins Cnls nd ditches Monitoring wells Autumn 212 Drins Cnls nd ditches Monitoring wells Spring 213 Drins Cnls nd ditches Monitoring wells Conclusion There ws high concentrtion of orthophosphte-p in drins compred to the orthophosphte- P in cnls nd ditches until spring 213. For the monitoring wells, decrese in orthophosphte- P cn be seen from utumn 211 to utumn 213, with the exception of utumn 212 where the verge P incresed. Totl P is lso lower in spring 212 in comprison with utumn 211. This is due to the fct tht the concentrtion of DIP in the wter smples nd soil wter is lower in spring 212 compred to utumn 211, while the concentrtion of DOP is more or less constnt in time. In spring 213 in lmost ll of the smples the mount of DIP ws below detection limit. 1 Orgnic crbon in the soil profile On ll prcels of the derogtion monitoring network stndrd soil smple ws tken in spring 212. On this stndrd soil smple different prmeters were nlysed (soil texture, ph, C, P, K, Mg, C, N). Bsed on the stndrd soil smple fertilistion dvice ws formulted for ech prcel for the next 3 yers. The %C mesured in the stndrd soil smple is shown in Tble 71. Since stndrd soil smple is tken from to 6 cm for grsslnd nd from to 23 cm for mize nd other crops, the results re given seprtely for both crops. 24

243 % of smples Tble 71: Averge vlue for %C mesured in the soil lyer from -6 cm for grss nd -23 cm for other crops in spring 212. Distinction is mde between derogtion nd no derogtion prcels. The number of prcels is indicted by n. %C n Derogtion (min, mx) n No derogtion (min, mx) All crops (.78, 6.48) (.6, 4.87) Derogtion crops (.78, 6.48) (.6, 4.87) Grss (1.8, 6.48) (.96, 4.87) Mize (.78, 3.37) (.6, 3.17) In Figure 27 the percentge of derogtion nd no derogtion prcels is shown for different %C soil fertility clsses. Most of the derogtion nd no derogtion prcels re clssified s optiml Derogtion No derogtion Figure 27: Percentge of derogtion nd no derogtion smples in different soil fertility clsses for the prmeter %C in spring

244 1.1 Orgnic crbon in the stndrd soil smple, prcels which were continuously under derogtion/no derogtion during In order to verify the long-term impct of derogtion on the orgnic crbon in the soil, only prcels tht were continuously under derogtion/no derogtion during were retined. Tble 72 shows the verge vlues for the percentge of orgnic crbon of derogtion nd no derogtion prcels nd for different crops. Tble 72: Averge %C mesured in the soil lyer from -6 cm for grss nd -23 cm for other crops in spring 212, only for prcels which were under derogtion/no derogtion during Distinction is mde between derogtion nd no derogtion prcels. The number of prcels is indicted by n. %C n Derogtion (min, mx) n No derogtion (min, mx) All crops (.82, 6.48) (.6, 4.87) Derogtion crops (.82, 6.48) (.96, 4.87) Grss (1.2, 6.48) (.96, 4.87) Mize (1.14, 3.37) (.6, 1.74) 1.2 Conclusion The men orgnic crbon in the soil profile in 212 (Tble 71) is higher for ll crops under derogtion (2.37 %) thn for ll crops under no derogtion (1.8 %). However, when looking more in detil to the cultivted crops, for prcels cultivted with grss the %C is lmost equl for derogtion nd no derogtion prcels. For prcels cultivted with mize derogtion prcels hve slightly higher %C in comprison to no derogtion prcels. The men orgnic crbon in the soil profile in 212, for prcels continuously under derogtion/no derogtion (29-211) cultivted with ll crops is 2.63 % for prcels under derogtion nd 1.81 % for prcels under no derogtion. 242

245 11 Burns model During winter there is little nutrient uptke by the cultivted crops. In this period, one of the most importnt soil processes is leching. This soil process my be influenced by different fctors nd strts when the soil profile hs reched field cpcity. In order to investigte the leching of nitrte during winter, soil smple is tken in utumn nd spring. These nitrte soil smples re discussed in the previous prgrphs. Often when studying leching, the Burns model (Burns, 1974) is used to predict the movement of unbsorbed nions, such s nitrte, in freely drined soils. The nitrte trnsfer is clculted from the mount of wter movement through the soil profile on proportionl bsis. Nitrte is dissolved in wter nd the trnsport through the soil is identiclly to the trnsport of wter due to the specific chrcteristics of nitrte (no bsorption) Input prmeters For the Burns model, different prmeters re required s input. For ech prcel of the monitoring network, the combintion of these prmeters is unique. The most importnt nd necessry prmeters re: - rinfll nd evportion (wter blnce); - nitrte in the soil profile; - thickness of the different soil lyers; - field cpcity (depending on soil texture nd importnt for wter retention cpcity); - smpling dte. Bsed on these prmeters, the mount of nitrogen leching out is clculted over specific period. Since leching occurs when the soil profile is bove field cpcity, it is importnt to know the moisture content of the soil smples t the moment of smpling. Since the Burns model is not suited for cly soils, the leching on prcels with cly texture is not reported. On ech prcel in the monitoring network nitrte smple ws tken in the different soil lyers of 3 cm (lyer 1: -3 cm, lyer 2: 3-6 cm nd lyer 3: 6-9 cm) from October 1 st to Mrch 15 th. So the thickness of the different soil lyers used in the model is 3 cm. Results of these nitrte residue mesurements re discussed erlier in this report. 243

246 Since nitrte only leches out if wter is supplied to the soil, rinfll is very importnt prmeter. For ech wether sttion it is importnt tht the observed dt re complete. Only the wether sttions where 95 % or more of the rinfll dt were vilble from October to Mrch, were retined. For the dtes where no rinfll dt were vilble from these sttions, the men of rinfll of the region of Flnders ws used for tht specific dte. Another importnt fctor for the wter blnce is evpotrnspirtion. Clcultions for ETo re vilble from different sttions. However, sttions without dt of ETo, or if one dte is missing, re replced in this nlysis by the men ETo of the region of Flnders for specific dte. An overview of the different sttions with observtions for rinfll nd evpotrnspirtion re listed in Tble 73. Tble 73: Overview of the selected sttions for the wether observtions for rinfll nd evpotrnspirtion (ETo). Rinfll ETo Winter Beuvechin Beuvechin ; ; Beitem Men of Flnders ; Bierset Bierset ; ; Deurne Deurne ; ; Gorsem Men of Flnders ; Herent Men of Flnders ; ; Kleine Brogel Kleine Brogel ; ; Koksijde Koksijde ; ; Kruishoutem Men of Flnders ; Melsbroek Melsbroek ; ; Middelkerke Middelkerke ; ; Pssendle Men of Flnders ; ; Semmerzke Semmerzke ; ; Sint-Ktelijne-Wver Men of Flnders ; ; Stbroek Men of Flnders ; Tienen Men of Flnders ; ; Ukkel Ukkel ; ; By using the rinfll nd ETo dt, wter blnce (rinfll - evpotrnspirtion) is clculted for ech retined wether sttion for specific month. The wter blnce for ech wether sttion is summrized in Tble 74 for winter , in Tble 75 for winter nd in Tble 76 for winter for the most importnt months during winter. Mostly the wter blnce is positive for the months October, November, December, Jnury nd Februry. 244

247 Tble 74: Wter blnce (rinfll evpotrnspirtion, L/m²) for the different wether sttions for different months-winter Oct/11 Nov/11 Dec/11 Jn/12 Feb/12 Mrch/12 Beuvechin Beitem Bierset Deurne Herent Kleine Brogel Koksijde Kruishoutem Melsbroek Middelkerke Pssendle Semmerzke Sint-Ktelijne-Wver Stbroek Tienen Ukkel The negtive wter blnce for November in utumn 211 is explined by wether conditions mentioned in Annex 3-Climte 211(Figure 244, Figure 245, Figure 246). Tble 75: Wter blnce (rinfll evpotrnspirtion, L/m²) for the different wether sttions for different months-winter Oct/12 Nov/12 Dec/12 Jn/13 Feb/13 Mrch/13 Beuvechin Bierset Deurne Gorsem Herent Kleine Brogel Koksijde Melsbroek Middelkerke Pssendle Semmerzke Sint-Ktelijne-Wver Tienen Ukkel

248 Tble 76: Wter blnce (rinfll evpotrnspirtion, L/m²) for the different wether sttions for different months-winter Oct/13 Nov/13 Dec/13 Jn/14 Feb/14 Mrch/14 Beuvechin Beitem Bierset Deurne Gorsem Herent Kleine Brogel Koksijde Kruishoutem Melsbroek Middelkerke Pssendle Semmerzke Sint-Ktelijne-Wver Stbroek Tienen Ukkel Winter Ech prcel of the network is linked to combintion of the 3 closest wether sttions which were retined nd the dt re the result of weighed verge of the observtions t the 3 wether sttions. The Burns model results in n mount of nitrte-n leching out, for ech soil lyer of 3 cm. For nitrte fter leching clculted with Burns (utumn 211 to spring 212), rinfll dt re used until the prcels were smpled in spring 212. Since utumn ws very dry, soils where not t field cpcity in utumn 212. Therefore the mount of rinfll needed in order to rech field cpcity ws clculted for ech soil texture. This mount of necessry rinfll ws deducted from the mount of rinfll on ech prcel in December. After winter, the lowest levels re present in sndy soils nd highest in lom soils. Since ll soils hve certin minerlistion cpcity, the soil will relese nitrogen from the orgnic mtter during winter. Therefore, in Tble 77 the estimted vlues of nitrte-n with Burns re shown with nd without correction for minerlistion. 246

249 Tble 77: Averge mount of nitrte-n (kg N/h) estimted with the Burns model for different soil textures, with or without minerlistion. The end dte of leching with Burns is the dte of the mesured nitrte soil smple spring 212. The verge mounts of nitrte-n (kg N/h) mesured in spring 212 re lso shown. Without minerlistion Nitrte-N (kg/h) fter leching out (Burns) -3 cm 3-6 cm 6-9 cm -9 cm Snd Sndy lom Lom With minerlistion Nitrte-N (kg/h) fter leching out (Burns) -3 cm 3-6 cm 6-9 cm -9 cm Snd Sndy lom Lom Mesured Nitrte-N (kg/h) in spring cm 3-6 cm 6-9 cm -9 cm Snd Sndy lom Lom When we compre these results with the vlues mesured in spring 212, vlues clculted with the Burns model re lower. This difference is lrgest for sndy soils. The clcultions with the Burns model re n underestimtion of the effective mesured nitrte in the soil profile fter winter, certinly in sndy soils. During leching, nitrte-n migrtes from the upper soil lyers to the deeper soil lyers. As consequence, fter winter the soil lyer from to 3 cm hs very low levels of nitrte-n. The result of the Burns model is n mount of nitrte leving the upper soil lyer nd moving to the lower soil lyers. This process is identicl for ech soil lyer. Finlly this results in n mount of nitrte-n leving the soil profile t 9 cm nd n mount of nitrte-n still present in every soil lyer. Results of the estimted nitrte present in the soil fter winter clculted with Burns (both with nd without minerlistion) nd the mesured vlues fter winter for ech prcel nd for different soil types nd derogtion/no derogtion re summrized in Tble

250 Tble 78: Results of the clcultions by the Burns model in comprison with mesured mount of nitrte-n (kg/h) in the soil profile (-9 cm), spring 212. The end dte of leching with Burns is the dte of the mesured nitrte soil smple in spring 212. Clculted with Burns (nitrte-n kg/h) Mesured without minerlistion with minerlistion fter winter Snd Derogtion Snd No derogtion Sndy lom Derogtion Sndy lom No derogtion Lom Derogtion Lom No derogtion Figure 28 illustrtes the reltion between the mesured nd the estimted mount of nitrte-n (kg/h) with the Burns model, spring 212 with corrections for minerlistion tken into ccount. When we compre these results, for most of the prcels the Burns model mkes n overestimtion of the leching of nitrte-n nd the estimted nitrte-n fter winter is lower thn the mesured vlues. Sctterplot of mesured nitrte-n versus estimted nitrte-n (Burns) Y = *x; R² =.32 ; p <.1 18 Nitrte-N (kg/h) fter winter estimted (Burns) Nitrte-N (kg/h- mesured fter winter Figure 28: Sctterplot of nitrte-n (kg/h) mesured in spring 212 versus the nitrte-n (kg/h) estimted by the Burns model until the dte of the nitrte soil smple in spring 212, with corrections for minerlistion. 248

251 Figure 29 shows sctterplot of the mount of nitrte-n in utumn 211 minus spring 212, versus the mount of nitrte tht leched out ccording to Burns. Since some prcels were smpled in Mrch, there ws lredy minerlistion on the prcels, resulting in negtive vlues for nitrte in utumn 211 minus spring 212. Sctterplot of nitrte in utumn 211 minus spring 212 versus estimted leching with Burns Y = *x ; R² =.72 ; p <.1 Nitrte (kg N/h) leched out ccording to Burns Nitrte (kg N/h) before minus fter winter 211 Figure 29: Sctterplot of nitrte-n (kg/h) mesured in utumn 211 minus spring 212 versus the nitrte- N (kg/h) estimted by the Burns model including minerlistion. Next, we will investigte if there re ny sttisticl differences in nitrte leching out of the soil profile clculted with Burns, between derogtion nd no derogtion prcels cultivted with grss or mize. The leching on mize prcels is lrger thn on grss prcels (Tble 79). There is no significnt difference in leching of nitrte estimted by Burns between derogtion nd no derogtion prcels cultivted with grss or mize. 249

252 Tble 79: Results of the estimted leching by the Burns model in winter for grss nd mize prcels. A one-wy ANOVA (p.5) on the log-trnsformed dt ws crried out for grss nd mize seprtely. Clculted with Burns (nitrte-n kg/h) Derogtion (min,mx) No derogtion (min,mx) p-vlue Grss 44.5 (3.8; 163.5) 44.1 (.4; 245.1).42 Mize 7.7 (17.3; 199.5) 71.8 (4.3; 243.8) Winter Ech prcel of the network is linked to combintion of the 3 closest sttions which were retined nd the dt re the result of weighed verge of the observtions between the 3 sttions. The Burns model results in n mount of nitrte-n leching out, for ech soil lyer of 3 cm. For nitrte fter leching clculted with Burns, rinfll dt re used until the prcels were smpled in spring 213. In Tble 8, the estimted vlues of nitrte-n with Burns re shown with nd without correction for minerlistion tken into ccount. Tble 8: Averge mount of nitrte-n (kg N/h) estimted with the Burns model for different soil textures, with or without minerlistion. The end dte of leching with Burns is the dte of the mesured nitrte soil smple in spring 213. The verge mount of nitrte-n (kg N/h) mesured in spring 213 is lso given. Without minerlistion Nitrte-N (kg/h) fter leching out (Burns) -3 cm 3-6 cm 6-9 cm -9 cm Snd Sndy lom Lom With minerlistion Nitrte-N (kg/h) fter leching out (Burns) -3 cm 3-6 cm 6-9 cm -9 cm Snd Sndy lom Lom Mesured Nitrte-N (kg/h) spring cm 3-6 cm 6-9 cm -9 cm Snd Sndy lom Lom

253 The clcultions with Burns including minerlistion re good estimtion of the mount of nitrte in the soil profile fter winter for sndy lom soils, n underestimtion for sndy soils nd n overestimtion for lom. During leching, nitrte-n migrtes from the upper soil lyers to the deeper soil lyers. As consequence, fter winter the soil lyer from to 3 cm hs very low levels of nitrte-n. The result of the Burns model is n mount of nitrte leving the upper soil lyer nd moving to the lower soil lyers. This process is identicl for ech soil lyer. Finlly this results in n mount of nitrte-n leving the soil profile t 9 cm nd n mount of nitrte-n still present in every soil lyer. Figure 21 illustrtes the reltion between the mesured nd the estimted mount of nitrte-n (kg/h) in spring with the Burns model, with corrections for minerlistion tken into ccount. A significnt correltion exists between the nitrte-n in spring 213 mesured nd estimted with Burns. The regression model explined 83 % of the vrince. Nitrte-N (kg/h) mesured in spring Sctterplot of mesured nitrte-n versus estimted nitrte-n (Burns) Y = *x, R² =.82, p< Nitrte-N (kg/h) in spring 213 estimted (Burns) Figure 21: Sctterplot of nitrte-n (kg/h) mesured in spring 213 versus the nitrte-n (kg/h) estimted by the Burns model until the dte of the nitrte soil smple in spring 213, including minerlistion. 251

254 Next, we will investigte if there re ny sttisticl differences in nitrte leching out of the soil profile clculted with Burns, between derogtion nd no derogtion prcels cultivted with grss or mize. Therefore, n ANOVA (p.5) nlysis ws crried out on the log-trnsformed dt. The leching on mize prcels is lrger thn on grss prcels (Tble 81). There is no significnt difference in leching of nitrte estimted by Burns between derogtion nd no derogtion prcels cultivted with grss or mize. Tble 81: Results of the estimted leching by the Burns model in winter for grss nd mize prcels. A one-wy ANOVA (p.5) on the log-trnsformed dt ws crried out for grss nd mize seprtely. Clculted with Burns (nitrte-n kg/h) Derogtion (min,mx) No derogtion (min,mx) p-vlue Grss 35.6 (7.7; 111.3) 3.9 (9.2; 61.2).22 Mize 54.6 (21.4; 118.8) 44.9 (13.5; 141.9) Winter Ech prcel of the network is linked to combintion of the 3 closest sttions which were retined nd the dt re the result of weighed verge of the observtions between the 3 sttions. The Burns model results in n mount of nitrte-n leching out, for ech soil lyer of 3 cm. For nitrte fter leching clculted with Burns, rinfll dt re used until the prcels were smpled in spring 214. In Tble 82, the estimted vlues of nitrte-n with Burns re shown with nd without correction for minerlistion tken into ccount. For winter the clcultions with Burns without minerlistion were good estimtion of the mount of nitrte in the soil profile fter winter for sndy lom nd lom soils. For sndy soils the clcultion with Burns without minerlistion resulted in n underestimtion of the mount of nitrte-n in the soil profile fter winter. The mount of nitrte-n in the soil profile fter winter on sndy soils ws best estimted with Burns tken minerlistion into ccount. 252

255 Tble 82: Averge mount of nitrte-n (kg N/h) estimted with the Burns model for different soil textures, with or without minerlistion. The end dte of leching with Burns is the dte of the mesured nitrte soil smple in spring 214. The verge mount of nitrte-n (kg N/h) mesured in spring 214 is lso given. Without minerlistion Nitrte-N (kg/h) fter leching out (Burns) -3 cm 3-6 cm 6-9 cm -9 cm Snd Sndy lom Lom With minerlistion Nitrte-N (kg/h) fter leching out (Burns) -3 cm 3-6 cm 6-9 cm -9 cm Snd Sndy lom Lom Mesured Nitrte-N (kg/h) spring cm 3-6 cm 6-9 cm -9 cm Snd Sndy lom Lom During leching, nitrte-n migrtes from the upper soil lyers to the deeper soil lyers. As consequence, fter winter the soil lyer from to 3 cm hs very low levels of nitrte-n. The result of the Burns model is n mount of nitrte leving the upper soil lyer nd moving to the lower soil lyers. This process is identicl for ech soil lyer. Finlly this results in n mount of nitrte-n leving the soil profile t 9 cm nd n mount of nitrte-n still present in every soil lyer. Figure 211 illustrtes the reltion between the mesured nd the estimted mount of nitrte-n (kg/h) in spring 214 with the Burns model, with corrections for minerlistion tken into ccount. The correltion between the nitrte-n mesured in spring 214 nd the nitrte-n estimted with Burns ws sttisticlly significnt but only 9 % of the vrince is explined by the model. When minerlistion ws not tken into ccount in the clcultion with Burns, the correltion between the mesured nd estimted nitrte-n (Figure 212) ws lso sttisticlly significnt nd the model explined only 11 %. 253

256 18 Sctterplot of mesured nitrte-n versus estimted nitrte-n (Burns) Y = 33,1887+,458*x; R²=,86; p<,5 Nitrte-N (kg/h) in spring 214 estimted Burns Nitrte-N (kg/h) mesured in spring 214 Figure 211: Sctterplot of nitrte-n (kg/h) mesured in spring 214 versus the nitrte-n (kg/h) estimted by the Burns model until the dte of the nitrte soil smple in spring 214, including minerlistion. 12 Sctterplot of mesured nitrte-n versus estimted nitrte-n (Burns) Y=9,565+,357*x, R²=,11, p<,5 Nitrte-N (kg/h) in spring 214 estimted (Burns) Nitrte-N (kg/h) mesured in spring 214 Figure 212: Sctterplot of nitrte-n (kg/h) mesured in spring 214 versus the nitrte-n (kg/h) estimted by the Burns model until the dte of the nitrte soil smple in spring 214, minerlistion not tken into ccount. 254

257 Next, we will investigte if there re ny sttisticl differences in nitrte leching out of the soil profile clculted with Burns, between derogtion nd no derogtion prcels cultivted with grss or mize. Therefore, n ANOVA (p.5) nlysis ws crried out on the log-trnsformed dt. The leching on mize prcels is lrger thn on grss prcels (Tble 83). There is no significnt difference in leching of nitrte estimted by Burns between derogtion nd no derogtion prcels cultivted with grss or mize. Tble 83: Results of the estimted leching by the Burns model in winter for grss nd mize prcels. A one-wy ANOVA (p.5) on the log-trnsformed dt ws crried out for grss nd mize seprtely. Clculted with Burns (nitrte-n kg/h) Derogtion (min,mx) No derogtion (min,mx) p-vlue Grss 66.4 (7.; 292.8) 57.4 (13.; 2.).38 Mize 8. (13.7; 252) 66.6 (11.8; 178.6) Conclusion The Burns model estimtes the mount of nitrte leching out of the soil profile. For individul prcels, lrge differences between clculted nd mesured nitrte levels re sometimes present. Correltions were found between the nitrte-n mesured in spring nd the nitrte-n clculted with Burns for spring 212, spring 213 nd spring 214. There is no significnt difference in nitrte-n leching out during winter clculted with Burns between derogtion nd no derogtion prcels, neither for prcels cultivted with mize nor for prcels cultivted with grss on ll soil types. This lck of sttisticl significnt difference ws found in winter , winter nd winter

258 12 Nutrient blnce For ech prcel in the monitoring network nutrient blnce is clculted. A nutrient blnce tries to explin nitrte residue levels on the prcels nd nitrte concentrtions in wter smples. Moreover, differences in nutrient blnces for derogtion nd no derogtion prcels will be explored more in detil. Two different pproches re used to clculte nutrient blnce: the input/output blnce nd nitrogen-soil blnce Input/output blnce The first pproch for clculting nutrient blnce is the difference between the effective input nd output of nutrients on prcel level. The input comprises orgnic nd minerl fertiliser ppliction, s well s tmospheric deposition. Nutrients re exported by mens of the hrvested crop nd emission losses during orgnic fertiliser ppliction (Tble 84). The result of this blnce is n indictor for the enrichment or impoverishment of nutrients in the soil profile. Tble 84: Schemtic presenttion of the input/output nutrient blnce. Input Output Orgnic fertilisers Hrvested crop Minerl fertilisers Emission during fertilistion Atmospheric deposition Blnce = input output Input of orgnic nd minerl fertilisers Detiled informtion on the input of orgnic nd minerl fertilisers for the different yers is given in prgrph 5.2. The totl mounts of supplied nutrients (N nd P) s well s the different frctions (minerl, orgnic nd orgnic by grzing cttle) re given seprtely for derogtion nd no derogtion prcels nd for ech cultivted crop Input of tmospheric deposition For ll the prcels in the monitoring network tmospheric deposition occurs during the seson. This tmospheric deposition is the sme for ll prcels in the monitoring network nd is estimted t 3 kg N/h ech yer. 256

259 Output of emission losses During ppliction of orgnic mnure some emission losses will occur. The method of fertilistion ppliction is the most determining prmeter. These emission losses re shown in Tble Output of the hrvested crop Hrvest of the cultivted crop is the most importnt nutrient export fctor. So yield dt re the most importnt dt. Yield dt re reported by the prticipting frmers. Bsed on the dry mtter, nitrogen nd phosphorus content, the mount of exported nutrients cn be clculted. The effective nutrient content is not known; therefore the figures shown in Tble 85 nd Tble 86 re used. Tble 85: Amount of nitrogen nd phosphorus for ech ton dry mtter nd fresh weight (moisture content of the hrvested crop is given). Levels re seprtely given for different crops. Source: Ontwerp ctieprogrmm nitrtrichtlijn ². Dry mtter (DM) Yield kg N /ton DM kg P 2O 5 /ton DM kg N /ton yield kg P 2O 5 /ton yield Moisture (%) Pottoes Tubers Winter whet Grin Winter brley Grin Sugr beets Beets Fodder beets Beets Corn mize Corn Tble 86: Amount of nitrogen nd phosphorus exported by the hrvest of silge mize (bove-ground) for different clsses of yield. Yield (bove-ground) Dry mtter (ton/h) N (kg/h) P (kg P 2 O 5 /h) Very poor Poor Good Very good For winter whet, sugr beets, pottoes nd corn mize the yield ws mostly communicted s n mount of kilogrmme for ech prcel. By using Tble 85 the mount of nitrogen nd phosphorus (kg/h) exported by the cultivted crops cn be clculted for ech prcel. For silge 257

260 mize the exct yield (kg/h) for ech prcel is not lwys vilble. The silge mize is hrvested nd stored together for mny prcels. In some cses n exct yield is known but for the other prcels it is n estimtion nd yield clsses re used to estimte the yield of the different prcels. Therefore the numbers in Tble 86 re used. Another difficult crop to estimte the yield is grss. For prcels cultivted with grss different possibilities re present: cutting, cutting nd grzing cttle or only grzing cttle. The required informtion is given by the frmers. When cutting the grss, the yield for ech cutting hs to be estimted, lmost none of the frmers hs n exct weight of the grss fter hrvest. Therefore the numbers in the next tble (Tble 87) re used. Tble 87: Amount of nitrogen nd phosphorus exported by the grsslnd (bove-ground) for ech cutting with specific level of yield. Yield (bove-ground) Dry mtter (ton/h) N (kg/h) P (kg P 2 O 5 /h) Very poor Poor Good Very good Besides the cultivted crop, nutrient export is lso possible by the ctch crop sown fter hrvest. To estimte the nutrient uptke by the ctch crop Tble 88 is used. Tble 88: Export of nitrogen (kg N/h) for different stges of development nd for different types of ctch crop sown fter hrvest of the cultivted crop. Development of ctch crop little good very good Ctch crop, lef Ctch crop, grss Ctch crop, N fixtion (Source: prktijkgids bemesting bij suikerbieten) Blnce result 212 The result of the input-output blnce 212 is shown in Tble 89. Blnce results re very vrible t prcel level: some prcels hve positive vlues for the blnce where others hve negtive. An ANOVA nlysis ws mde in order to notify sttisticl differences for derogtion 258

261 nd no derogtion prcels cultivted with different crops. For prcels cultivted with mize, no sttisticl difference is found between derogtion nd no derogtion prcels, not for N (p =.47), nor for P 2 O 5 (p =.79). For prcels cultivted with grss, sttisticl difference is found between derogtion nd no derogtion prcels, both for N nd P 2 O 5 (p <.5). For beets, no sttisticl nlysis ws mde since only 1 beet prcel is present. Tble 89: N-blnce (input-output), P-blnce (input-output) nd nitrte residue for derogtion nd no derogtion prcels-yer 212. N (input-output) P 2 O 5 (input-output) Nitrte residue Derogtion Mize Grsslnd Beets Winter whet No derogtion Mize Grsslnd Beets Winter whet Pottoes Grphs were mde in order to estimte the percentge of ech fctor of the nutrient blnce (orgnic fertilisers, minerl fertilisers, tmospheric deposition, hrvested crop nd emission during fertilistion) in function of the totl input. Figure 213 shows this for mize under derogtion nd under no derogtion. For both groups, input by orgnic fertilistion is the most importnt input. Both on derogtion nd no derogtion prcels the output exceeds the totl input. On no derogtion prcels even the export by only the mize is 1 % higher thn the totl input while for derogtion prcels the export by the crop is 97 % of the totl input. Figure 214 shows the percentge of ech fctor in function of the totl input in the input/output blnce for grss under derogtion nd under no derogtion. On derogtion prcels 44 % of the totl input is of orgnic fertilistion. On grss prcels without derogtion orgnic fertilistion is 35 % of the totl input. Export of the grss on no derogtion prcels exceeds the totl input with 48 %. 259

262 % N input % N input 16 Mize, derogtion exp cover crop exp crop deposition orgnic fert minerl fert Tot N input Tot N output 16 Mize, no derogtion exp cover crop exp crop deposition orgnic fert minerl fert Tot N input Tot N output Figure 213: Percentge of ech fctor in reltion to the totl input in the input/output blnce for prcels cultivted with mize under derogtion nd no derogtion-yer

263 % N input % N input 16 Grss, derogtion exp crop deposition grzing orgnic fert minerl fert Tot N input Tot N output 16 Grss, no derogtion exp crop deposition grzing orgnic fert minerl fert Tot N input Tot N output Figure 214: Percentge of ech fctor in reltion to the totl input in the nutrient blnce for prcels cultivted with grss under derogtion nd no derogtion-yer 212. Next, the correltion between the blnce result (input-output) for nitrogen nd the nitrte residue is shown in Figure 215. The correltion between the input-output blnce nd the nitrte residue for the growing seson 212 is not strong. Some importnt soil processes re not tken into ccount in this blnce model in order to link the nitrte residue to fertilistion nd nutrient 261

264 uptke by the crops. By mens of nitrogen-soil blnce (see next prgrph), these soil processes re discussed. 16 Correltion between nitrte residue nd input-output blnce R²=,4; p=, Nitrte residue (kg N/h) Input-output blnce (kg N/h) Figure 215: Nitrte residue versus Input-output blnce for the growing seson of 212 for ll prcels Blnce result 213 The result of the input-output blnce 213 is shown in Tble 9. The vribility of blnce results between prcels ws still high. On grss prcels lrge difference ws found between the men blnce result of prcels with mowing nd grzing nd grss prcels with only mowing. These differences re shown in Tble 91. An ANOVA nlysis ws mde in order to notify sttisticl differences between derogtion nd no derogtion prcels in function of the cultivted crop. For prcels cultivted with mize no sttisticl difference ws found between derogtion nd no derogtion, nor for N (p =.63), nor for P 2 O 5 (p =.15). For prcels cultivted with grss sttisticl significnt difference ws detected between derogtion nd no derogtion prcels for P 2 O 5 (p <.5) but not for N (p =.23). 262

265 Tble 9: N-blnce (input-output), P-blnce (input-output) nd nitrte residue for derogtion nd no derogtion prcels-yer 213. N (input-output) P 2 O 5 (input-output) Nitrte residue Derogtion Mize Grsslnd Beets Winter whet No derogtion Mize Grsslnd Beets Winter whet Pottoes Tble 91: N-blnce (input-output), P-blnce (input-output) nd nitrte residue for derogtion nd no derogtion prcels cultivted with grss with grzing nd mowing or only mowing-yer 213. N (input-output) P 2 O 5 (input-output) Nitrte residue Derogtion Grss-grzing & mowing Grss-mowing No derogtion Grss-grzing & mowing Grss-mowing Grphs were mde in order to visulize the shre of ech fctor of the nutrient blnce (orgnic fertilisers, minerl fertilisers, tmospheric deposition, hrvested crop nd emission during fertilistion) in function of the totl input. Figure 216 shows this for mize under derogtion nd under no derogtion. For both groups, input by orgnic fertilistion is the most importnt input. On derogtion nd no derogtion prcels the output exceeds the totl input with respectively 5 nd 3 %. On no derogtion prcels the export by only the mize is higher thn the totl input, like ws noticed for the input/output blnce in 212. For derogtion prcels the export by the min crop is 84 % of the totl input. Figure 217 shows the percentge of ech fctor in function of the totl input in the input/output blnce for grss under derogtion nd under no derogtion. On derogtion prcels 37 % of the totl input is of orgnic fertilistion nd 15 % input by grzing. On grss prcels without derogtion orgnic fertilistion is 29 % of the totl input. Export of the grss on both derogtion prcels nd no derogtion prcels ws smller thn the totl input. 263

266 % N input % N input 12 Mize, derogtion exp cover crop exp crop deposition orgnic fert minerl fert Tot N input Tot N output 12 Mize, no derogtion exp cover crop exp crop deposition orgnic fert minerl fert Tot N input Tot N output Figure 216: Percentge of ech fctor in reltion to the totl input in the input/output blnce for prcels cultivted with mize under derogtion nd no derogtion-yer

267 % N input % N input 12 Grss, derogtion exp crop deposition grzing orgnic fert minerl fert Tot N input Tot N output 12 Grss, no derogtion exp crop deposition grzing orgnic fert minerl fert Tot N input Tot N output Figure 217: Percentge of ech fctor in reltion to the totl input in the nutrient blnce for prcels cultivted with grss under derogtion nd no derogtion-yer 213. In contrst to the results of 212, the correltion between the nitrte residue nd the result of the input-output blnce ws sttisticlly significnt. However the regression explins only 3 % of the vribility (Figure 218). 265

268 25 Correltion between nitrte residue nd input-output blnce R²=.349; p=.2 2 Nitrte residue (kg N/h) Input-output blnce (kg N/h) Figure 218: Nitrte residue versus Input-output blnce for the growing seson of 213 for ll prcels Blnce result 214 The result of the input-output blnce 214 is shown in Tble 92. The vribility of blnce results between prcels ws high. On grss prcels lrge difference ws found between the men blnce result of prcels with mowing nd grzing nd grss prcels with only mowing. These differences re shown in Tble 93. An ANOVA nlysis ws conducted in order to notify sttisticl differences in blnce result between derogtion nd no derogtion prcels in function of the cultivted crop. For prcels cultivted with grss no sttisticl difference ws found between derogtion nd no derogtion, nor for N (p =.93), nor for P 2 O 5 (p =.51). For prcels cultivted with mize sttisticl significnt difference ws detected between derogtion nd no derogtion prcels for P 2 O 5 (p <.5) but not for N (p =.12). For beets nd winter whet no sttisticl comprison is mde between derogtion nd no derogtion prcels since the number of prcels ws too limited. 266

269 Tble 92: N-blnce (input-output), P-blnce (input-output) nd nitrte residue for derogtion nd no derogtion prcels-yer 214. N (input-output) P 2 O 5 (input-output) Nitrte residue Derogtion Mize Grsslnd Beets Winter whet No derogtion Mize Grsslnd Beets Winter whet Pottoes Tble 93: N-blnce (input-output), P-blnce (input-output) nd nitrte residue for derogtion nd no derogtion prcels cultivted with grss with grzing nd mowing or only mowing-yer 214. N (input-output) P 2 O 5 (input-output) Nitrte residue Derogtion Grss-grzing & mowing Grss-mowing No derogtion Grss-grzing & mowing Grss-mowing Grphs were mde in order to visulize the shre of ech fctor of the nutrient blnce (orgnic fertilisers, minerl fertilisers, tmospheric deposition, hrvested crop nd emission during fertilistion) in function of the totl input. Figure 219 shows this for mize under derogtion nd under no derogtion. For both groups, input by orgnic fertilistion is the most importnt input. On derogtion nd no derogtion prcels the output exceeds the totl input with respectively 3 nd 25 %. On both types of prcels the export by only the mize is higher thn the totl input. On no derogtion prcels the export by the mize ccounted for 123 % of the totl input. On derogtion prcels the export by the min crop is 16 % of the totl input. The export by the cover crop ws 24 % of the totl input on derogtion prcels compred to 3 % on no derogtion prcels. 267

270 % N input % N input 14 Mize, derogtion exp cover crop exp crop deposition orgnic fert minerl fert Tot N input Tot N output 14 Mize, no derogtion exp cover crop exp crop deposition orgnic fert minerl fert Tot N input Tot N output Figure 219: Percentge of ech fctor in reltion to the totl input in the input/output blnce for prcels cultivted with mize under derogtion nd no derogtion-yer 214. Figure 22 shows the percentge of ech fctor in function of the totl input in the input/output blnce for grss under derogtion nd under no derogtion. On derogtion prcels 38 % of the totl input is of orgnic fertilistion nd 11 % input by grzing. On grss prcels without derogtion orgnic fertilistion is 3 % of the totl input. Export of the grss on both derogtion 268

271 % N input % N input prcels nd no derogtion prcels ws ner to the totl input. On derogtion prcels the export ws 11 % of the totl input, 74 % by cuttings nd 27 % by grzing. On no derogtion prcels the export of the grss ws 16 % of the totl input, 61 % by cutting the grss nd 45 % by grzing cttle. 14 Grss, derogtion exp crop deposition grzing orgnic fert minerl fert Tot N input Tot N output 14 Grss, no derogtion exp crop deposition grzing orgnic fert minerl fert Tot N input Tot N output Figure 22: Percentge of ech fctor in reltion to the totl input in the nutrient blnce for prcels cultivted with grss under derogtion nd no derogtion-yer

272 The correltion between the nitrte residue nd the result of the input-output blnce ws not sttisticlly significnt (p =.97) s shown in Figure 221. However there is one prcel with high nitrte residue (381 kg N/h) while the blnce result ws rther low (-61 kg N/h). This prcel ws mize prcel which ws converted fter 7 yers being grsslnd. Since the inputoutput blnce does not comprise minerlistion the blnce result will not show the effect of n enhnced minerlistion fter converting the grss. The nitrte residue on the contrry, shows the effect of the enhnced minerlistion. Leving this prcel out of the dtset in order to revel possible correltion, resulted in sttisticlly significnt correltion between the nitrte residue nd the result of the input-output blnce (Figure 222). However like in 213 the regression explins only 3 % of the vribility. 4 Correltion between nitrte residue nd input-output blnce R²=.187; p= Nitrte residue (kg N/h) Input-output blnce (kg N/h) Figure 221: Nitrte residue versus Input-output blnce for the growing seson of 214 for ll prcels. 27

273 3 Correltion between nitrte residue nd input-output blnce R²=.332; p=.3 25 Nitrte residue (kg N/h) Input-output blnce (kg N/h) Figure 222: Nitrte residue versus Input-output blnce for the growing seson of 214, converted grss prcel excluded Nitrte-N soil blnce The second pproch is the nitrte-n soil blnce, where the nitrte-n in the soil profile is monitored during the growing seson. This blnce strts with the mount of nitrte t the beginning of the seson nd ends with the nitrte residue t the end of the seson. This is schemticlly represented in Tble 94. Tble 94: Schemtic overview of the different fctors influencing the evolution of nitrte-n in the soil profile during the growing seson. Input N in soil profile, begin of seson N from minerl fertiliser N from orgnic fertiliser Output N uptke by cultivted crop Leching out of N N from tmospheric deposition Minerlistion (from orgnic mtter) Blnce = input output N in soil profile, end seson (nitrte residue) 271

274 Nitrte in the soil profile before the growing seson The nitrte in the soil profile before the growing seson is the strting point for clculting the nitrte blnce. Nitrte is mesured on ll prcels of the monitoring network t the beginning of the growing seson. The smples re tken from to 9 cm in three lyers. This nitrte smple gives informtion bout the mount of nitrogen in the soil profile vilble for the cultivted crop, since mostly t this point no fertilisers re pplied yet. The mount of nitrte in the soil profile before the growing seson cn be seen in prgrph Fertilistion (orgnic nd minerl) The mount of nitrogen tht will be vilble during the growing seson originting from orgnic fertilistion (orgnic fertilisers nd grzing cttle) nd minerl fertilistion is n importnt fctor for clculting the nutrient blnce. In the first pproch (input/output blnce) the totl mount of nitrogen supplied on the prcels ws tken into ccount. For this second pproch, the nitrogen which is vilble for the plnt during the growing seson (= the effective mount of nitrogen) is of gret importnce. For orgnic fertilisers, informtion on the effective nitrogen is present in the nlysis report of the mnure smples (tken by SSB for the different types of orgnic mnure). In generl coefficient of 6 % is used to clculte the plnt vilble nitrogen from niml mnure or other orgnic fertilisers. For solid mnure, this coefficient is 3 %. For excretion by grzing cttle, the coefficient is 2 % nd for minerl fertilisers coefficient of 1 % is used Minerlistion An importnt mount of nitrogen will become vilble during the growing seson due to minerlistion. Orgnic fertilistion Some of the nitrogen present in orgnic fertilisers is only plnt vilble fter minerlistion hs occurred. This mount is clculted by the working coefficients of the orgnic mnure nd results in n mount of effective nitrogen (12.2.2). The mount of effective nitrogen consists of the minerl frction (directly plnt vilble), nd the frction which will be vilble during the growing seson due to minerlistion. For solid mnure, n importnt frction of the nitrogen 272

275 present in the orgnic mnure becomes vilble by minerlistion during the second yer fter ppliction. Soil orgnic mtter The most importnt source of minerlistion origintes from the soil orgnic mtter. The mount of nitrogen relesed during the growing seson is influenced by different prmeters, from which the two most importnt ones re soil texture nd the percentge of crbon. By using dt from the N-(eco)² project (Herelixk et l., 22; Tble 95) it is possible to estimte the mount of N relesed from the soil orgnic mtter in function of soil texture, percentge crbon nd smpling dte. The highest levels of minerlistion re found in the cly soils nd sndy soils; the lowest levels in sndy lom nd lom soils. Tble 95: Estimted monthly N minerlistion (kg N/h) of soil orgnic mtter in function of percentge crbon nd soil texture on rble lnd (source: N-(eco)²). Levels re presented for optiml conditions of soil humidity nd temperture. Soil texture %C Jn Feb Mrch April My June July Aug Sept Okt Nov Dec Sum Snd Sndy lom Lom Cly Bsed on Tble 95, nitrte from minerlistion of soil orgnic mtter is clculted for ech prcel. For ech prcel the percentge crbon nd soil texture re known. The minerlistion of soil orgnic mtter is clculted for the period between the nitrte smple t the beginning of the seson (spring yer x) nd the nitrte residue smple t the end of the growing seson (utumn yer x). This wy the minerlistion of soil orgnic mtter in yer x is clculted. 273

276 Ctch crop Minerlistion of the ctch crop sown fter the cultivted crop in yer x-1 is nother source of minerlised nitrogen. For cultivting mize with derogtion the presence of ctch crop is requirement. Since the requirement of hrvesting one cut of the ctch crop, minerlistion of the ctch crop will be rther smll. On prcels cultivted with mize without derogtion ctch crop is not lwys present. If grss is cultivted before mize without derogtion there s no requirement of hrvesting the ctch crop. Minerlistion of the ctch crop cn be importnt if not hrvested. Amounts of nitrogen originting from minerlistion of the ctch crop re bsed on Tble 96. Tble 96: N-relese (kg N/h) by different ctch crops (source: Wgeningen UR, 25). Type ctch crop Length (cm) Efficient N (kg/h) different moment of relesed for incorportion Before winter After winter Rye-grss Crucifere Leguminous Crop residues Other orgnic mteril tht will be minerlised re crop residues. Minerlistion of crop residues will be only importnt for some crops nd depends on the time period between the hrvest of the cultivted crop nd the moment of smpling fter winter. Especilly for beets, culiflower, sprouts, pes nd bens minerlistion of crop residues will be importnt. The crbon-nitrogen rtio of these crop residues is low, which mens tht minerlistion will be fst. If hrvest is more thn two months before the moment of smpling the prcel, prt of the nitrogen will be minerlised nd will be mesured in the profile t the beginning of the growing seson. In this cse the expected minerlistion for these crops rnges between 2 nd 3 kg 274

277 nitrte-n/h. If less thn two months between smpling the profile nd hrvest, the expected minerlistion will be higher Uptke by the cultivted crop In this pproch, both the mount of nitrogen exported by the hrvest nd the mount of nitrogen tken up by the prts of the cultivted crops tht re not hrvested re tken into ccount for the clcultion of the nutrient blnce. For grsslnd nd mize, these re mostly the roots. For some other crops it cn be the leves (sugr beet). Especilly for beets the mounts of nitrogen extrcted from the soil profile by not hrvested prts (leves) is considerble. Tble 97: Amount of nitrogen (kg N/h) nd phosphorous (kg P 2O 5/h) uptke by the roots nd leves of different cultivted crops. The levels re bsed on verge yields. Source: Ontwerp ctieprogrmm nitrtrichtlijn Averge yield N-uptke P 2 O 5 -uptke Pottoes Leves 41 Pottoes Roots 1 Winter whet Strw Winter whet Roots 3 Winter brley Strw 23 1 Winter brley Roots 3 Sugr beets Leves 15 Sugr beets Roots 1 Fodder beets Leves Fodder beets Roots 1 Corn mize Strw 48 Corn mize Roots 25 Silge mize Roots 25 1 cut of grss Roots 2 Grss (mowing) Roots 45 Grss (mowing + grzing) Roots Leching nd tmospheric deposition During the growing seson the process of leching is less importnt in comprison with the winter period. From the dte of smpling t the beginning of the yer till the moment of ctive nutrient tke up by the cultivted crops, leching is still possible, especilly for rble lnd. The process of leching is lso importnt fter hrvest or when crop growth is stopped. Leching during the growing seson is relted to the cultivted crop nd will be complex 275

278 clcultion. More informtion is necessry to clculte leching during the growing seson. Most importnt is the moisture content of the soil during the growing seson. Another fctor is tmospheric deposition. This is lmost the sme on ll prcels in the monitoring network. To clculte the nitrogen/soil blnce the effect of leching during the growing seson (nitrte output) nd the effect of tmospheric deposition (nitrte input) re not tken into ccount Nitrte residue The nitrte residue in the soil profile t the end of the seson is the lst prmeter which is tken into ccount t the output side. The nitrte residue is mesured on ll prcels between October 1 st nd November 15 th Nitrte-N soil blnce results 212 For the prcels in the monitoring network, nutrient blnce ws clculted. Results of the clcultions re shown in Tble 98. Tble 98: Nitrte-N soil blnce result of 212 for the most importnt derogtion nd no derogtion crops. Blnce result Derogtion Mize 2 Grsslnd 36 Beets -85 Winter whet - No derogtion Mize 3 Grsslnd -86 Beets - Winter whet 72 Pottoes -31 For mize, the nitrte soil blnce lmost equls, both for derogtion nd no derogtion prcels. However when looking t individul prcels, the nutrient blnce for mize prcels rnges from 23 to -185 kg N/h. There is no significnt difference in nitrte soil blnce result 276

279 for mize prcels under derogtion nd no derogtion (p =.67). There is significnt difference in nitrte-n soil blnce between derogtion nd no derogtion prcels cultivted with grss. Grphs were lso mde in order to estimte the percentge of ech fctor of the nutrient blnce (Nitrte in the beginning of the seson, nitrte from soil minerlistion, minerl fertilistion, orgnic fertilistion, grzing, export by cultivted crop, export by cover crop nd nitrte in the end of the seson) in function of the totl input. Figure 223 shows this for mize under derogtion nd under no derogtion. For both groups the input by soil minerlistion is the most importnt input fctor, followed by the orgnic fertilistion. Export by the cultivted crop recovers 62 % of the totl input on mize prcels with derogtion. On mize prcels without derogtion 74 % of the totl input is recovered by the cultivted crop. 277

280 % input % input Mize, derogtion Exp cover crop Exp crop Orgnic fert Minerl fert Minerlistion Begin of seson Tot N input N output crops End of seson Mize, no derogtion Exp cover crop Exp crop Orgnic fert Minerl fert Minerlistion Begin of seson Tot N input N output crops End of seson Figure 223: Percentge of ech fctor in the nitrte-n/soil blnce for prcels cultivted with mize under derogtion nd no derogtion-yer 212. Figure 224 shows the percentge of ech fctor of the nitrte-n soil blnce in function of the totl N input for grss under derogtion nd under no derogtion. For both groups, the input by soil minerlistion is the highest input. On derogtion prcels cultivted with grss, 83 % of the totl N input ws recovered by the cultivted crop. On grss prcels without derogtion the N- output by the cultivted crop exceeded the totl N-input with 17 %. 278

281 % input % input Grss, derogtion Exp crop Grzing Orgnic fert Minerl fert Minerlistion Begin of seson Tot N input N output crops End of seson Grss, no derogtion Exp crop Grzing Orgnic fert Minerl fert Minerlistion Begin of seson Tot N input N output crops End of seson Figure 224: Percentge of ech fctor in the nitrte-n/soil blnce for prcels cultivted with grss under derogtion nd no derogtion-yer Nitrte-N soil blnce results 213 For the prcels in the monitoring network, lso the nitrte-n blnce of 213 is clculted. Results of the clcultions re shown in Tble 98. When looking t individul prcels, the nutrient blnce for mize prcels rnges from -27 to 14 kg N/h. 279

282 There is no significnt difference in nitrte soil blnce result for mize prcels under derogtion nd no derogtion (p =.1) in 213. Also for prcels cultivted with grss there is no sttisticl significnt difference between prcels with or without derogtion (p =.72). Tble 99: Nitrte-N soil blnce result of 213 for the most importnt derogtion nd no derogtion crops. Blnce result Derogtion Mize 21 Grsslnd 18 Beets - Winter whet 58 No derogtion Mize -5 Grsslnd 1 Beets - Winter whet 78 Pottoes 43 The prcel which showed result of -27 for the nitrte-n soil blnce ws prcel cultivted with silge mize without derogtion on sndy soil (Tble 1). Tble 1: Nitrte-N soil blnce 213 no derogtion prcel cultivted with mize on sndy soil, converted of grsslnd into croplnd in spring 212. Mize, no derogtion, sndy soil Nitrte in soil 8/2/ Uptke mize hrvest-export 26 roots 25 Fertilistion orgnic 53 minerl 81 Ctch crop spring utumn 213 Minerlistion Soil orgnic mtter 129 Solid mnure Residue 9/1/ Ctch crop Crop residue Result nitrte-n soil blnce

283 The good hrvest resulted in n export of 26 kg N/h. Despite the high N-export high nitrte residue ws found t 9 October 213. The blnce result supposes n underestimtion of the N- input. The history of the prcel cn explin the high nitrte residue nd the underestimtion of the minerlistion of soil orgnic mtter. The prcel ws converted of grsslnd into croplnd in spring 212. Grphs were mde in order to visulize the shre of ech fctor of the nutrient soil blnce (nitrte in the beginning of the seson, nitrte from minerlistion, minerl fertilistion, orgnic fertilistion, grzing, uptke by cultivted crop, uptke by cover crop nd nitrte in the end of the seson) in function of the totl input. Figure 225 shows this for mize under derogtion nd under no derogtion. For both groups the input by soil minerlistion is confirmed to be the most importnt input fctor. Orgnic fertilistion is 3 nd 28 % of totl input on mize prcels with nd without derogtion respectively. On mize prcels under derogtion in 213, 66 % of the totl N-input is recovered by the mize nd 16 % by the ctch crop. On prcels cultivted with mize without derogtion 79 % of the totl N-input is recovered by the mize but only 2 % by ctch crop. 281

284 % input % input Mize-derogtion Output cover crop Output crop Orgnic fert Minerl fert Minerlistion Begin of seson Tot N input N output crops End of seson Mize-no derogtion Output cover crop Output crop Orgnic fert Minerl fert Minerlistion Begin of seson Tot N input N output crops End of seson Figure 225: Percentge of ech fctor in the nitrte-n soil blnce for prcels cultivted with mize under derogtion nd no derogtion-yer 213. Figure 226 shows the percentge of ech fctor of the nitrte-n soil blnce in function of the totl N input for grss under derogtion nd not under derogtion. Like for mize prcels lso for both groups of prcels cultivted with grss, input by soil minerlistion is the highest input. Orgnic fertilistion is bout 21 % of totl N-input on both derogtion nd no derogtion prcels. On both derogtion nd no derogtion prcels cultivted with grss, 86 % of the totl N- input ws recovered by N-uptke of the grss. 282

285 % input % input Grss, derogtion Output crop Grzing Orgnic fert Minerl fert Minerlistion Begin of seson Tot N input N output crops End of seson Grss, no derogtion Output crop Grzing Orgnic fert Minerl fert Minerlistion Begin of seson Tot N input N output crops End of seson Figure 226: Percentge of ech fctor in the nitrte-n soil blnce for prcels cultivted with grss under derogtion nd no derogtion-yer Nitrte-N soil blnce results 214 Like in 212 nd 213 the nitrte-n soil blnce of 214 is clculted for the prcels in the monitoring network. Results of the clcultions re shown in Tble 11. There is no significnt difference in nitrte-n soil blnce result for mize prcels under derogtion nd no derogtion 283

286 (p =.77) in 214. Also for prcels cultivted with grss there is no sttisticl significnt difference between prcels with or without derogtion (p =.92). Tble 11: Nitrte-N soil blnce result of 214 for the most importnt derogtion nd no derogtion crops. Blnce result Derogtion Mize -24 Grsslnd 5 Beets Winter whet -14 No derogtion Mize -17 Grsslnd 8 Beets -7 Winter whet 15 Pottoes 55 Grphs were mde in order to visulize the shre of ech fctor of the nutrient soil blnce (nitrte in the beginning of the seson, nitrte from minerlistion, minerl fertilistion, orgnic fertilistion, grzing, uptke by cultivted crop, uptke by cover crop nd nitrte in the end of the seson) in function of the totl input. Figure 227 shows this for mize under derogtion nd under no derogtion. For both groups the input by soil minerlistion is the most importnt input fctor s shown erlier. Orgnic fertilistion is 3 nd 26 % of totl input on mize prcels with nd without derogtion respectively. On mize prcels under derogtion in 214, 75 % of the totl N-input is recovered by the mize nd 18 % by the ctch crop. On prcels cultivted with mize without derogtion 83 % of the totl N-input is recovered by the mize but only 3 % by ctch crop. 284

287 % input % input Mize-derogtion Output cover crop Output crop Orgnic fert Minerl fert Minerlistion Begin of seson Tot N input N output crops End of seson Mize-no derogtion Output cover crop Output crop Orgnic fert Minerl fert Minerlistion Begin of seson Tot N input N output crops End of seson Figure 227: Percentge of ech fctor in the nitrte-n/soil blnce for prcels cultivted with mize under derogtion nd no derogtion-yer 214. Figure 228 shows the percentge of ech fctor of the nitrte-n soil blnce in function of the totl N input for grss under derogtion nd not under derogtion. Like for mize prcels lso for both groups of prcels cultivted with grss, the input by soil minerlistion is the highest input. Orgnic fertilistion is 16 nd 21 % of totl N-input on no derogtion nd derogtion prcels respectively. On both derogtion nd no derogtion prcels cultivted with grss, bout 9 % of the totl N- input ws recovered by N-uptke of the grss. 285

288 % input % input Grss, derogtion Output crop Grzing Orgnic fert Minerl fert Minerlistion Begin of seson Tot N input N output crops End of seson Grss, no derogtion Output crop Grzing Orgnic fert Minerl fert Minerlistion Begin of seson Tot N input N output crops End of seson Figure 228: Percentge of ech fctor in the nitrte-n soil blnce for prcels cultivted with grss under derogtion nd no derogtion-yer Yield smpling In Vndervelpen et l. (211) s well s in the current monitoring study it is shown tht huge devitions cn occur for individul prcels. Since nutrient uptke by the cultivted crop is determining fctor, s shown for the different nutrient blnces, less ccurte estimtion of the yield is one possible reson for berrtions in the nutrient blnces. 286

289 Therefore more ccurte estimtion of yield nd nutrient export is imed by yield smpling t grss nd mize prcels nd determintion of the dry mtter content nd the N- nd P-content of the crop. Ten prcels with grsslnd nd 1 mize prcels were selected Grsslnd-213 For the grss prcels it ws ment to hrvest the first two cuttings. Fresh yield, dry mtter content nd N nd P content re determined to rech better insight in N nd P-export per h per yer for grsslnd. In grss prcels were selected. On ll prcels the first cut ws smpled. At 4 rndomly selected sites in the prcels the crop ws hrvested on 5-1 m². The crop smples were nlysed for dry mtter content, N nd P content. Hrvesting the second cut wsn t lwys possible. Becuse wether conditions re determining crop growth nd the moment of hrvest, some prcels were lredy hrvested before smpling ws possible while other prcels were no longer ment to mow but for grzing. The results of the yield smpling t the first cut show dry mtter yields of ton/h representing N-export of kg N/h nd P 2 O 5 -export of kg P 2 O 5 /h. Tble 12: Results of yield smpling of the 2 first cuttings on 1 grss prcels of the monitoring network in 213, dry mtter yield (ton/h) nd the mount of nutrients exported by the crop (kg N/h, kg P 2O 5/h). Cut 1 N crop (kg N/h) Cut2 N crop (kg N/h) Dry mtter (ton/h) P 2 O 5 crop (kg P 2 O 5 /h) Dry mtter (ton/h) Derogtion b c d e f g No derogtion P 2 O 5 crop (kg P 2 O 5 /h) 287

290 For the second cut, yield smpling ws done on only 4 prcels. These results lso confirm the lrge differences in yield between prcels. Dry mtter yield rnged from 1.3 to 4.5 ton/h. The rnge for N nd P-export ws kg N/ h nd kg P 2 O 5 /h. The nitrte-n soil blnces in Figure 229 tke the yield smpling on the grss prcels into ccount. For some prcels the blnce result ws ner to zero. On prcels b nd d the result of the nitrte-n soil blnce ws very good. For these prcels the informtion of the yield communicted by the frmers ws detiled nd the result of the blnce bsed on these figures ws lredy ner to zero. Prcels nd c were lso grzed, which cretes uncertinty bout the export by grzing. On prcel c nimls were on the prcel until 6 dys before the prcel ws smpled in utumn. This could explin the high nitrte residue. The orgnic N-input mounted for 13 to 33 % of the totl N-input. The N-output by the crop mounted 84 to 17 % of the totl N-input. For prcel c the output by the crop ws limited to only 54 %. For two prcels the nitrte-n soil blnce could not be mde becuse of incomplete informtion. 288

291 % input % input % input % input % input % input % input 12 1 Blnce= -42 b 12 1 Blnce= Tot N input N output crops End of seson Tot N input N output crops End of seson c 12 1 Blnce= -4 d 12 1 Blnce= Tot N input N output crops End of seson Tot N input N output crops End of seson e 12 1 Blnce= -4 f 12 1 Blnce= Tot N input N output crops End of seson Tot N input N output crops End of seson g Blnce= 21 Output crop Grzing 6 4 Orgnic fert Minerl fert 2 Minerlistion Begin of seson Tot N input N output crops End of seson Figure 229: Nitrte-N soil blnces for prcels with yield smpling of grss, percentge of ech fctor reltive to totl input-yer

292 Mize prcels-213 Ten mize prcels of the monitoring network were selected nd on ech prcel 2 rows of 4 m t 5 rndomly chosen sites in the prcel were hrvested. The results showed lrge vribility between the prcels. The lrgest dry mtter yield ws 2.5 ton/h while the smllest hrvest ws only 11.7 ton dry mtter/h (Tble 13). The vribility in dry mtter content nd N content resulted in N export by the crop of 14.5 kg N/h to kg N/h. For phosphorus n export rnge of kg P 2 O 5 ws mesured. Tble 13: Results of yield smpling on mize prcels in 213, dry mtter yield (ton/h) nd the mount of nutrients exported by the crop (kg N/h, kg P 2O 5/h). Dry mtter (ton/h) N crop (kg N/h) P 2 O 5 crop (kg P 2 O 5 /h) Derogtion b c d e f g No derogtion h Figure 23 shows the nitrte-n soil blnce of the prcels on which yield smples re tken. These nitrte-n soil blnces tke the results of the yield smpling into ccount. A more ccurte estimtion of the nutrient export resulted in better blnce results. The blnce results were ner to zero. Prcel c showed despite the yield smpling, blnce result of 146. On this prcel the N-export ws only 15 kg N/h, fr below the verge, cused by low yield nd low N-content of the crop. For two prcels nitrte-n soil blnce could not be mde becuse incomplete informtion. The orgnic N-input mounted for % of the totl N-input. The N-export by the mize mounted for % of the totl N-input. 29

293 % input % input % input % input % input % input % input % input 12 1 Blnce=15 b 12 1 Blnce= Tot N input N output crops End of seson Tot N input N output crops End of seson c 12 1 Blnce=146 d 12 1 Blnce= Tot N input N output crops End of seson Tot N input N output crops End of seson e 12 1 Blnce=45 f 12 1 Blnce= Tot N input N output crops End of seson Tot N input N output crops End of seson g 12 1 Blnce=-3 h 12 1 Blnce= Tot N input N output crops End of seson Tot N input N output crops End of seson Crop residue Exp cover crop Exp crop Orgnic fert Minerl fert Minerlistion Begin of seson 16-4 Figure 23: Nitrte-N soil blnces for prcels with yield smpling of mize, percentge of ech fctor reltive to totl input-yer

294 Grsslnd-214 For the yield smpling on prcels cultivted with grss, 1 prcels were selected. Frmers were contcted nd it ws greed to smple the two first cuttings of the grss. However hrvesting grss is often n urgent decision in period with lot of work on the field nd high time pressure. On some prcels only one cut could be smpled nd on other prcels even the third cut ws smpled. The crop smples were nlysed for dry mtter content, N nd P content. The results of the yield smpling t the first cut show n verge dry mtter yield of 3.6 ton/h. Dry mtter yields rnged from only.61 ton/h to 4.85 ton/h (Tble 14). Differences in dry mtter yield nd N-content resulted in rnge of N-export of to kg N/h t the first cut. P 2 O 5 -export t the first cut ws situted between 7.57 nd kg P 2 O 5 /h. For the second cut, yield smpling ws done on only 4 prcels. Tble 14: Results of yield smpling on 1 grss prcels of the monitoring network in 214, dry mtter yield (ton/h) nd the mount of nutrients exported by the crop (kg N/h, kg P 2O 5/h). Dry mtter (ton/h) Cut 1 Cut 2 Cut 3 N crop (kg N/h) P 2O 5 crop (kg P 2O 5/h) Dry mtter (ton/h) N crop (kg N/h) P 2O 5 crop (kg P 2O 5/h) Dry mtter (ton/h) N crop (kg N/h) P 2O 5 crop (kg P 2O 5/h) Derogtion b c d e f g No derogtion h i These results confirm the lrge differences in yield between prcels. Dry mtter yield t the second cut rnged from 2.17 to 5.44 ton/h. The rnge for N nd P-export ws respectively kg N/ h nd kg P 2 O 5 /h. At the third cut, smpled on two prcels, in verge 3.3 ton of dry mtter is hrvested, nd kg N nd kg P 2 O 5 /h re exported. The nitrte-n soil blnces mde up regrding to the yield smpling (Figure 231 nd Tble 15), were negtive (output higher thn input) for 4 prcels out of 6. Prcels b, e nd f show high input combined with high output nd rther low nitrte residue. On prcels g nd h the 292

295 % input % input % input % input % input % input lower input resulted in clerly lower output. Prcel h ws grzed. The N-export by grzing is lower thn in mowing system. For three prcels the nitrte-n soil blnce could not be mde becuse of incomplete informtion Blnce= 88 b 12 1 Blnce= Tot N input N output crops End of seson Tot N input N output crops End of seson e 12 1 Blnce= -43 f 12 1 Blnce= Tot N input N output crops End of seson Tot N input N output crops End of seson g 12 1 Blnce= -27 h 12 1 Blnce= Tot N input N output crops End of seson Tot N input N output crops End of seson Begin of seson Minerlistion Minerl fert Orgnic fert Grzing Output crop Figure 231: Nitrte-N soil blnces for prcels with yield smpling of grss, percentge of ech fctor reltive to totl input-yer

296 Tble 15: Nitrte-N soil blnces for prcels with yield smpling of grss, mount of nitrte-n by fctor of input/output, yer Grss-only mowing, derogtion, sndy soil b-grss-only mowing, derogtion, sndy lom soil Nitrte in soil 28/3/ Uptke grss hrvest-export 343 Nitrte in soil 15/2/ Uptke grss hrvest-export 5 roots 45 roots 45 Fertilistion orgnic 144 Ctch crop spring 214 Fertilistion orgnic 173 Ctch crop spring 214 minerl 243 utumn 214 minerl 191 utumn 214 grzing grzing Minerlistion soil orgnic mtter 28 Minerlistion soil orgnic mtter 95 Solid mnure Solid mnure ctch crop ctch crop crop residue crop residue Residue 2/1/ Residue 8/1/ Result nitrte-n soil blnce 88 Result nitrte-n soil blnce -63 e-grss-only mowing, derogtion, cly soil f-grss-only mowing, derogtion, sndy soil Nitrte in soil 3/1/ Uptke grss hrvest-export 47 Nitrte in soil 2/3/ Uptke grss hrvest-export 47 roots 45 roots 45 Fertilistion orgnic 151 Ctch crop spring 214 Fertilistion orgnic 145 Ctch crop spring 214 minerl 139 utumn 214 minerl 189 utumn 214 grzing grzing Minerlistion soil orgnic mtter 15 Minerlistion soil orgnic mtter 156 Solid mnure Solid mnure ctch crop ctch crop crop residue crop residue Residue 21/1/ Residue 1/1/ Result nitrte-n soil blnce -43 Result nitrte-n soil blnce -56 g-grss-only mowing, derogtion, sndy soil h-grss-grzing, no derogtion, sndy lom soil Nitrte in soil 31/1/214 5 Uptke grss hrvest-export 281 Nitrte in soil 19/2/ Uptke grss hrvest-export 24 roots 45 roots 4 Fertilistion orgnic 122 Ctch crop spring 214 Fertilistion orgnic Ctch crop spring 214 minerl 54 utumn 214 minerl 23 utumn 214 grzing grzing 24 Minerlistion soil orgnic mtter 129 Minerlistion soil orgnic mtter 112 Solid mnure Solid mnure ctch crop ctch crop crop residue crop residue Residue 2/1/ Residue 1/1/ Result nitrte-n soil blnce -27 Result nitrte-n soil blnce Mize prcels-214 Ten mize prcels of the monitoring network were selected nd on ech prcel mize is hrvested. Fresh weight ws mesured t the field nd dry mtter, N nd P content were mesured t the lbortory. At two prcels, nd h, yield smpling resulted in berrnt vlues. For those two prcels the results nd the nitrte-n soil blnce is not shown. The verge yield of dry mtter on the smpled mize prcels in utumn 214 ws 18. ton/h, compred to 15.6 ton in utumn 213. This confirms the overll expecttion of high yield of mize before the hrvest seson nd the overll experience of the frmers in the mize seson. Nevertheless n importnt vribility between the prcels is still noticed. The lrgest dry mtter 294

297 yield ws 22. ton/h while smller hrvests of only 14.5 ton dry mtter/h were mesured (Tble 16). The vribility in dry mtter content nd N content resulted in N export by the crop of 169 kg N/h to 255 kg N/h. For phosphorus n export rnge of kg P 2 O 5 ws mesured. Tble 16: Results of yield smpling on mize prcels in 214, dry mtter yield (ton/h) nd the mount of nutrients exported by the crop (kg N/h, kg P 2O 5/h). Dry mtter (ton/h) N crop (kg N/h) P 2 O 5 crop (kg P 2 O 5 /h) Derogtion berrrnt vlues b c d e No derogtion f g h berrrnt vlues i j For prcels d nd j informtion ws incomplete nd the nitrte-n soil blnce could not be mde. The result of the nitrte-n soil blnce ws positive (input higher thn output) for ll prcels on which the yield of the mize ws monitored. On prcels b, c nd e, derogtion prcels, the uptke of the ctch crop is obviously importnt. On the no derogtion prcels ( f, g, i ) in verge 63 % of the totl N input ws recovered by the mize. On the derogtion prcels ( b, c, e ) in verge 5 % of the totl N input ws recovered by the mize. However on these prcels the cover crop recovered 22 % of the totl N input. On the no derogtion prcels the cover crop recovered only 6 % of the totl N input. 295

298 % input % input % input % input % input % input b 12 1 Blnce = 23 c 12 1 Blnce = Tot N input N output crops End of seson Tot N input N output crops End of seson e 12 1 Blnce = 78 f 12 1 Blnce = Tot N input N output crops End of seson Tot N input N output crops End of seson g 12 1 Blnce = 65 i 12 1 Blnce = Tot N input N output crops End of seson Tot N input N output crops End of seson Output cover crop Output crop Orgnic fert Minerl fert Minerlistion Begin of seson Figure 232: Nitrte-N soil blnces for prcels with yield smpling of mize, percentge of ech fctor reltive to totl input-yer

299 Tble 17: Nitrte-N soil blnces for prcels with yield smpling of mize, mount of nitrte-n by fctor of input/output-yer 214. b-mize, derogtion, sndy soil c-mize, derogtion, sndy soil Nitrte in soil 28/1/14 24 Uptke mize hrvest-export 217 Nitrte in soil 29/1/14 16 Uptke mize hrvest-export 169 roots 25 roots 25 Fertilistion orgnic 115 Ctch crop spring Fertilistion orgnic 115 Ctch crop spring minerl 54 utumn 214 minerl 54 utumn 214 Minerlistionsoil orgnic mtter 215 Minerlistionsoil orgnic mtter 26 Solid mnure Solid mnure ctch crop ctch crop crop residue crop residue Residue 2/1/14 73 Residue 2/1/ Result nitrte-n soil blnce 23 Result nitrte-n soil blnce 59 e-mize, derogtion, sndy lom soil f-mize, no derogtion, sndy lom soil Nitrte in soil 1/2/14 2 Uptke mize hrvest-export 189 Nitrte in soil 11/2/14 1 Uptke mize hrvest-export 255 roots 25 roots 25 Fertilistion orgnic 117 Ctch crop spring Fertilistion orgnic 57 Ctch crop spring minerl 18 utumn minerl 255 utumn 214 Minerlistionsoil orgnic mtter 186 Minerlistionsoil orgnic mtter 134 Solid mnure Solid mnure ctch crop ctch crop crop residue crop residue Residue 6/1/14 54 Residue 14/1/ Result nitrte-n soil blnce 78 Result nitrte-n soil blnce 24 g-mize, no derogtion, sndy soil i-mize, no derogtion, sndy soil Nitrte in soil 26/2/14 33 Uptke mize hrvest-export 211 Nitrte in soil 1/3/14 34 Uptke mize hrvest-export 233 roots 25 roots 25 Fertilistion orgnic 94 Ctch crop spring Fertilistion orgnic 16 Ctch crop spring 214 minerl 6 utumn 214 minerl 2 utumn 214 Minerlistionsoil orgnic mtter 194 Minerlistionsoil orgnic mtter 194 Solid mnure Solid mnure ctch crop ctch crop 213 crop residue crop residue Residue 3/1/14 95 Residue 23/1/ Result nitrte-n soil blnce 65 Result nitrte-n soil blnce Nitrte-N/soil blnce of 21 nd nitrte in monitoring wells, bsed on the trvel time In Vndervelpen et l. (211), the nutrient blnce ws clculted for the growing seson of 21. Bsed on the trvel time of nitrte from the prcels to the groundwter, it could be expected tht positive nutrient blnce would result in more leching nd thus higher nitrte concentrtion in the groundwter. Therefore, correltion ws mde between the result of the nutrient blnce for the growing seson of 21 nd nitrte in the groundwter bsed on the trvel time. The result is shown in Figure

300 Correltion between nitrte soil blnce of growing seson 21 nd nitrte in the groundwter, bsed on the trvel time dj R² =.4; p <.5 Nitrte in the groundwter, bsed on trvel time (mg NO3/l) Nitrte soil blnce (kg N/h) Figure 233: Sctterplot of clculted nitrte soil blnce (kg N/h) versus nitrte in the groundwter, bsed on the trvel time (mg NO3/l). There is positive correltion between the result of the nitrte soil blnce nd the nitrte in the groundwter, bsed on the trvel time. Only 4 % of the vrince is explined by the model. This is probbly due to the fct tht lmost ll nitrte concentrtions in the groundwter re below the detection limit Conclusion The input/output blnce evlutes roughly the input nd the output. In 212 the output ws in verge higher thn the input. No correltion ws found between the result of the input/output blnce in 212. In 213 nd 214 the correltion between the nitrte residue nd the result of the input/output blnce ws sttisticl significnt. Higher blnce results (input higher thn output) correlted with higher nitrte residues. In 213 the result of the input/output blnce ws often positive (input higher thn output). The results of the nitrte-n soil blnce for derogtion nd no derogtion prcels do not differ significntly. 298

301 The yield smpling confirmed even on limited number of prcels, the high vribility in N- export. Not only dry mtter yield but lso the nitrogen content cn differ gretly which cn result in highly different N-export. More ccurte figures of yield nd N-export by yield smpling often help to relise more ccurte nutrient soil blnce of the individul prcel. However even when N-export is mesured the result of the nitrogen soil blnce will not lwys rech zero. The yield smpling is n dvntge for the individul prcel, but the berrtions relised in the nitrte- N soil blnces bsed on verge figures, will not be voided by yield smpling. Furthermore it needs to be mentioned tht result of zero for the nitrte-n soil blnce does not men tht ll fctors of the blnce re interpreted correctly. When different fctors re interpreted wrong, nd one is overestimted while the other one is underestimted, the result will still rech zero while the result could be negtive or positive. Although it s sometimes difficult to interpret, the nitrte-n soil blnce cn be useful instrument for declring the input nd output in more detil. 13 Simultion of the effect of derogtion on the level of Flnders Besides the monitoring of the possible effect of derogtion on wter qulity which cn t this moment lredy be mesured, it s lso opportune to look hed nd estimte the possible long term implictions of the possibility of derogtion on wter qulity. This wy it will be possible to ct not only curtive but lso pro-ctive ArcNEMO in generl The effect of derogtion on wter qulity in Flnders cn be estimted with ArcNEMO (Vn Opstl et l., 214). In this model, in first step, the effect on fertilistion on prcel level is estimted with the Fertiliser Alloction Model (BemestingsAlloctieModel, BAM), which ws developed for ArcNEMO. For this study, BAM ws run for the yers 21, 211 nd Generl procedure of BAM BAM clcultes the totl mount of fertiliser used per frm nd per yer nd ssigns it to the griculturl prcels of ech frm, tking into ccount the fertiliser type, the crop nd the corresponding fertilistion limit. 299

302 In first step, ll prcels re fertilised consecutively per crop type, mximlly up to the fertilistion limit (or until ll fertilisers of the frm hve been ssigned). The following order is used: first the mize prcels, then grss, pottoes, sugr beets, vegetbles, fruit, other crops, cerels, legumes. For the frms where not ll of the used fertiliser cn be ssigned in this wy, surplus fertilistion of mximum 15 % of the fertilistion limit is ssigned to the mize, grss, cerel nd legume prcels consecutively (second step). Finlly, the llocted fertilistion dosges on ll the prcels re corrected per frm either ccording to its totl fertiliser lloction cpcity (i.e. sum of prcel res multiplied by corresponding fertilistion limits) or ccording to its totl mount of fertiliser used (the most limiting of both criteri). This correction gurnties tht the totl mount of fertiliser used by ech frm is mximlly ssigned to its prcels, without exceeding its totl fertiliser lloction cpcity. In other words, the frm fertilistion blnce (fertiliser lloction cpcity ssigned fertiliser) will never be negtive. As consequence, if scenrio hs n impct on the fertiliser lloction cpcity, this impct will lso be visible in the clculted fertilistion on prcel level The no derogtion scenrio (scenrio 2) For the evlution of the effect of derogtion on the fertilistion t prcel level in Flnders, the results of scenrio without derogtion (scenrio 2) re compred to the results of reference scenrio (scenrio ). The reference scenrio (scenrio ) is bsed on the rel frm nd prcel dt (mnure production, fertiliser use, crops, mngement greement, grnted derogtion, ) of 21, 211 nd 212. For the determintion of the fertilistion limits for ech prcel, the stricter phosphorus limits pplicble from 218 were used: - Grsslnd (mowing): 9 kg P 2 O 5.h -1.yer -1 (insted of 95) - Grsslnd (mowing & grzing): 9 kg P 2 O 5.h -1.yer -1-1 grss cutting + mize: 9 kg P 2 O 5.h -1.yer -1 (insted of 95) - Mize: 7 kg P 2 O 5.h -1.yer -1 (insted of 8) - Winter whet nd triticle: 7 kg P 2 O 5.h -1.yer -1 (insted of 75) - Winter brley nd other cerels: 7 kg P 2 O 5.h -1.yer -1 - Other crops: 55 kg P 2 O 5.h -1.yer -1 (insted of 65) For the P-limits no distinction is mde between sndy nd non-sndy soils. 3

303 For P-sturted soils generl limit of 4 kg P 2 O 5.h -1.yer -1 is pplicble for ll the crops. For P- sturted soils with low P-binding cpcity the bove mentioned P-limits minus 1 kg P 2 O 5.h - 1.yer -1 re pplicble. The no-derogtion scenrio (scenrio 2) ws clculted with the sme frm nd prcel dt, but for the derogtion prcels, fertilistion limits of no derogtion prcels were pplied Results scenrio 2 Scenrio 2 hs cler effect on the totl fertiliser lloction cpcity in Flnders. Without derogtion the totl fertiliser lloction cpcity is lower for N from niml mnure, but higher for P 2 O 5 from minerl fertilizers (Figure 234) fertiliser lloction cpcity N (1 6 kg) fertiliser lloction cpcity P 2 O 5 (1 6 kg) N niml s N niml s2 N minerl s N minerl s2 P2O5 tot. s P2O5 tot. s2 P2O5 minerl s P2O5 minerl s2 Figure 234: Totl fertiliser lloction cpcity in Flnders for N nd P 2O 5 from niml mnure nd from minerl fertilisers. As consequence, BAM ssigns less niml mnure to griculturl prcels in scenrio 2 thn in the reference scenrio (scenrio ). As for N, this effect is prtilly compensted by slightly higher fertilistion with minerl fertilisers. As for P, fertilistion with minerl fertilisers is 31

304 significntly higher in scenrio 2 thn in the reference scenrio, due to the lrger fertiliser lloction cpcity of P from minerl fertilisers (Figure 235). Assigned N from niml mnure (1 6 kg) s s2 Assigned N minerl fertilisers (1 6 kg) s s2 Assigned P 2 O 5 niml mnure (1 6 kg) Assigned P 2 O 5 minerl fertilisers (1 6 kg) 5 s s2 6 s s Figure 235: Totl ssignment of N nd P 2O 5 from niml mnure nd from minerl fertilisers to griculturl prcels in Flnders, ccording to scenrio (red) nd scenrio 2 (green). The lower ssignment of niml mnure in scenrio 2 occurs minly on the mize nd grsslnd prcels. Therefore, becuse in derogtion frms less mnure cn be ssigned to mize nd grsslnd prcels, in some cses more mnure is vilble for the other crops, resulting in sometimes slightly higher fertilistion dosge for these other crops. The effects of scenrio 2 on the clculted (niml nd minerl) fertiliser dosges per crop is similr in the three yers (21, 211 nd 212). In the next figure the results per crop re shown for N nd P 2 O 5 in 212 (Figure 236). 32

305 35 N: verge fertilistion doses (kg.h -1 ) s2 N minerl s2 N niml s N minerl s N niml P 2 O 5 : verge fertilistion doses (kg.h -1 ) s2 P minerl s2 P niml s P minerl s P niml Figure 236: Averge clculted N nd P 2O 5 doses from niml mnure nd from minerl fertilisers per crop in 212, ccording to scenrio (red) nd scenrio 2 (green) Conclusion Animl mnure: In scenrio 2 lmost kg or 4,2 % less N from niml mnure is pplied to prcels thn in scenrio, on the level of Flnders. For P 2 O 5 from niml mnure the difference is smller: ± 3,6 % or 1,5.1 6 kg. Effective N: the lower mount of pplied N from niml mnure is prtilly compensted by slightly higher ppliction of minerl N. The difference in ppliction of totl effective N is on verge,8.1 6 kg or,8 % lower in scenrio 2 thn in scenrio. Totl P 2 O 5 : In scenrio 2 more P 2 O 5 from minerl fertilisers is pplied (+15 % or +,5.1 6 kg). The totl mount of pplied P 2 O 5 is only 2,3 % lower in scenrio 2 thn in scenrio. 33

306 The results of the BAM simultions indicte tht, on the level of Flnders, derogtion hs limited impct on the ppliction of niml mnure (+4 % with derogtion) nd minerl fertilisers (-1,6 % for N nd -15,2 % for P 2 O 5 with derogtion). This impct will probbly be more pronounced in regions with reltively more derogtion prcels, f.i. the regions of Brugse Polders, Gentse Knlen, Msbekken nd Netebekken. Therefore, simultions with the ArcNEMO model for the estimtion of the effect on wter qulity, will focus on these regions. 14 Process fctors for groundwter This section focuses on the clcultion nd nlysis of process fctors for groundwter for ech of the monitored field plots for which both residul nitrte contents nd nitrte concentrtions in the shllow groundwter were determined. The process fctor for groundwter is n empiricl dimensionless fctor tht quntifies the degree of dilution nd denitrifiction occurring from the moment tht the nitrte leches out of the root zone t 9 cm below the surfce until the moment tht it reches the groundwter (where it is being mesured with n observtion well) (Vn Overtveld et l., 211). Low process fctors ( 1) men tht the nitrte leched out of the root zone will be found in n lmost equl concentrtion in the groundwter, wheres high process fctors men tht the nitrte is diluted nd/or denitrified nd thus tht lower concentrtion will be mesured in groundwter. In Figure 237, the groundwter flow through hypotheticl cross section is shown. The process fctor for groundwter is the rtio between the verge nitrte concentrtion in the soil wter t -9 cm over the winter period nd the verge nitrte concentrtion mesured in monitoring well of the phretic groundwter tht receives the wter from the re where the nitrte concentrtion t the bottom of the root zone is determined. Similrly, process fctor for surfce wter cn be defined s the rtio between the verge nitrte concentrtion below the root zone t -9 cm nd the men nitrte concentrtion in the surfce wter recipient. In this study we only focussed on the process fctor for groundwter. The EU Nitrtes Directive (91/676/EEC) sttes tht the nitrte concentrtion in surfce wter - or groundwter should not exceed 5 mg NO 3 per litre of wter. Process fctors for ground wter re therefore useful men to determine the mximum nitrte concentrtion below the root zone of prcel, in order not to exceed this limit of 5 mg/l in the groundwter. 34

307 Figure 237: Schemtic representtion of groundwter flow nd process fctors relted to surfce wter nd groundwter. The process fctor for groundwter (GW) is defined s the rtio between the verge nitrte concentrtion below the root zone over the winter period nd the verge concentrtion in the groundwter monitoring well (yellow dotted line). A similr process fctor for surfce wter (OW) is defined s the rtio the verge nitrte concentrtion below the root zone nd the concentrtion in the surfce wter (red dotted line) (from Vn Overtveld et l., 211) Clcultion of the process fctor for groundwter Determintion of the rechrge zone of monitoring wells nd of trvel times from soil to well For ech monitoring well, the contributing rechrge re ws determined s n ellipticl region, upstrem of the smpling point, from which the wter mesured in the smpling point origintes with 75 % certinty (Figure 238). For ech smpling point, the trvel time through the unsturted nd sturted zone ws lso clculted. This ws chieved by clculting (i.e. bck-trcking) the flow line from the middle of the well to the wter divide bsed on groundwter mp for Flnders. Tht mp ws derived in 29 by kriging the vilble groundwter hed observtions nd using predictions from simple groundwter model tht ws constrined on wter levels in the surfce wter network. The mp ws obtined by combining both sources of informtion using Bysin Dt Fusion (Peeters et l., 21; Vn Overtveld et l., 211). Once the flow line through the well ws determined, the most likely position of the rechrge point of the monitoring well filter on the flow line (upstrem from the well) ws determined from the verticl position of the filter reltive to the phretic surfce nd the bse of the quifer. Sptil vribility in trnsmissivities implies tht flow lines 35

308 nd hence the rechrge point is subject to uncertinty. This considertion nd literture informtion on typicl sptil vrition of trnsmissivities led to the definition of n ellipticl region situted round the clculted rechrge point, from which the wter mesured in the smpling point origintes with 75 % certinty. The trvel time in the sturted zone (from the moment the soil wter reches the wter tble till the moment it reches the filter of the monitoring well) ws clculted from flow velocities nd the horizontlly trvelled distnce long the flow line. The trvel time in the unsturted zone (from soil surfce to phretic surfce) ws estimted s well by using the integrl form of the Drcy eqution (see section ) (Jury nd Horton, 24, eq. 3.42). All clcultions were performed in Mtlb R213 (The MthWorks Inc., Ntick, MA, USA). The full detils of the procedures nd theoreticl bckground is given by Vn Overtveld et l. (211). Figure 238: Aeril photogrph (Google Erth, Imge from Aerodt Interntionl Surveys) showing position of monitoring well (lbeled 231/231/16) nd the clculted rechrge point of the filter of the well (yellow plceholder). An ellipse round the clculted rechrge point delinetes the zone from which the wter mesured in the monitoring well origintes with 75 % certinty. 36

309 Clcultion of the verge nitrte concentrtion t the bottom of the root zone (-9 cm) Between October 1 st nd November 15 th soil smples were tken in the monitored frmers fields. In these soil smples the mount of nitrte in the soil profile from to 3, 3 to 6 cm nd 6 to 9 cm ws mesured, in order to determine the residul nitrte content. During winter there is little nitrte uptke by crops nd most of the residul nitrte leches out of the soil profile due to the precipittion excess (precipittion evpotrnspirtion) over the winter period. The verge nitrte concentrtion t -9 cm over the winter period for the fields tht contined the rechrge zone (75 % confidence ellipse) ws clculted from the mesured residul nitrte from to 3, 3 to 6 cm nd 6 to 9 cm using n nlyticl leching model (n nlyticl solution of the convection-dispersion eqution; Vn Overtveld et l., 211). The higher the residul nitrte, the higher is the predicted concentrtion, but other fctors tht influence the verge nitrte concentrtion t -9 cm over the winter period re (1) the precipittion excess over tht winter (precipittion- reference evpotrnspirtion from ET from November 1 st till Mrch 31 st ws given s input to the model, (2) the verticl distribution of the nitrte in the profile (mesured distribution of nitrte over the 3 lyers -3, 3-6 nd 6-9cm) nd (3) the fctors tht control the soil moisture content in the unsturted zone over the winter time (minly soil texture nd groundwter depth). Precipittion excess ws clculted for ech prcel. Ech prcel of the network is linked to combintion of the 3 closest wether sttions which were retined nd the dt re the result of weighed verge of the observtions between the 3 wether sttions. For ech wether sttion it is importnt tht the observed dt re complete. Only the wether sttions where 95 % or more of the rinfll dt were vilble from October to Mrch were retined. For the dtes where no rinfll dt were vilble from these sttions, the men of rinfll of the region of Flnders ws used for tht specific dte. Clcultions for ETo re vilble from different sttions. However, sttions without dt of ETo, or if one dte is missing, re replced in this nlysis by the men ETo of the region of Flnders for specific dte. An overview of the different sttions with observtions for rinfll nd evpotrnspirtion re listed in Tble

310 The soil mp unit of ech monitored field ws derived from the Belgin Soil Mp (scle 1:2). Next, representtive synthetic soil profile (with most common horizon sequence nd thickness, %snd, %silt, %cly, %C of ech lyer) ws derived for ech combintion of soil mp unit nd physicl soil region ( Centrle Vlmse lgvlkte, Kempische Cuest, ), using the soil dtbse Ardewerk (Vn Orshoven et l., 1993; Beckers et l., 211). Bulk density of ech soil lyer ws estimted using the pedotrnsfer function of Rwls (1983) in combintion with the minerl densities for the Belgin soil texturl clsses derived by Boon (1984) (See Vn De Vreken et l., 29, p. 53). Next the soil hydrulic properties (prmeters of the vn Genuchten-Mulem model) were clculted for ech lyer for ech synthetic soil profile from %snd, %silt, %cly, %C nd bulk density using the pedotrnsfer functions of Weynnts et l. (29). Using this informtion, the verticl vrition of the soil wter content in the winter period ws derived using the integrl form of the Drcy eqution (Jury nd Horton, 24, eq. 3.42), strting the upwrd integrtion from the mesured phretic surfce, nd ssuming stedy stte flow conditions with the verticl downwrd flux (mm/dy) clculted s the precipittion excess (mm) over the winter period (November 1 st to Mrch 31 st ) divided by the number of dys in tht period (151 dys). An nlyticl solution of the convection dispersion model given by Torride et l. (1993; 1995) ws finlly used to clculte the evolution of the flux-verged nitrte concentrtion t 9cm depth over the winter period (initil vlue problem with initil nitrte concentrtion derived from mesured residul nitrte, nd nitrte leching under stedy stte flow conditions in hlf-infinite soil column). This concentrtion ws next integrted over the precipittion excess to obtin the verge nitrte concentrtion t 9cm depth verged over the winter period. All clcultions were performed in Mtlb R213 (The MthWorks Inc., Ntick, MA, USA). The full detils of the procedures nd theoreticl bckground is given by Vn Overtveld et l. (211). As the residul nitrte ws mesured in the fll of 29, 21, 211, 212, nd 213, the verge nitrte concentrtions of ll monitored fields were clculted for the 5 winter periods tht followed the 5 smplings. 38

311 Clcultion of the process fctors The process fctor ws clculted s: where is the verge concentrtion t the bottom of the root zone (-9cm) t time t, nd is the concentrtion mesured in the monitoring well t time. is the trvel time of wter (nd hence of nitrte) from the bottom of the root zone to the filter of the monitoring well. It mens tht if the trvel time is, sy, 1.5 yers, the verge concentrtion t the bottom of the root zone over, sy, the winter period (i.e., centred round 15/1/21), hs to be compred with the nitrte concentrtion mesured in the monitoring well round 15/7/211 (1.5 yers lter). Nitrte concentrtions in the monitoring wells were mesured twice yer (in fll nd spring, tken s November 1 st nd My 1 st, respectively). To obtin concentrtion in the well round 15/7/211, weighted verge ws mde of the lst mesurement before nd fter tht dte (i.e. 1/5/211 nd 1/11/211). The closer the trget dte is to one of the mesurement dtes, the more weight is given to the vlue. In cse one of the two mesurements ws missing, the other mesurement ws used without ny verging. Since residul nitrte ws mesured ech fll from 29 till 214, nd nitrte mesurements in the monitoring wells were performed from fll 29 till spring 214, severl PF vlues could be clculted for most of the fields, the number depending on the trvel time of tht field. These vlues were then verged to obtin single PF vlue for ech field. Fields with trvel time longer thn 4 ½ yers were excluded s the monitoring period ws too short to hve mtching pir of nitrte concentrtions. Before performing the clcultions, the rechrge re of ll the wells ws clculted nd compred with the field boundry in Google Erth. Only fields where the confidence ellipse lrgely flls within the field boundry were retined. For few monitoring wells, the ellipse fell within 2 or 3 djcent fields tht were ll monitored. In this cse ws verged over these fields. A totl of 11 wells (82 VMM wells, 26 wells instlled for this study) were in this wy linked to fields of the monitoring network, nd could be used to clculte the PF. 39

312 Nitrte concentrtion t -9cm over winter period (mgno 3 /L) 14.2 Results nd discussion Reltionship between mesured residul nitrte content nd soil solution nitrte concentrtion t -9cm The residul nitrte content of the soil is the dominnt fctor tht controls the clculted soil solution nitrte concentrtion t -9cm over the winter period, but the results lso indicte differences between fields (soil texture, groundwter depth, precipittion excess), nd smll differences between yers (precipittion excess nd groundwter depth) (Figure 239). For residul nitrte content of 9 kg NO - 3 -N/h (the min threshold in Flnders), soil solution nitrte concentrtion t -9 cm were predicted to rnge between 7 nd 16 mg NO - 3 /L (horizontl dotted lines in Figure 239). In order to bring the nitrte concentrtion down from 7 mg NO - 3 /L to 5 mg NO - 3 /L in groundwter monitoring well, the PF should hve vlue of t lest 1.4 (=7/5). To bring the concentrtion down from 16 to 5 mg NO - 3 /L, the PF should be t lest 3.2 (=16/5) Residul nitrte (kg NO 3 -N/h in -9cm in fll) Figure 239: Reltionship between the residul nitrte content mesured in fll nd the clculted verge nitrte concentrtion in the soil wter t depth of -9cm (verged over the winter period following the residul nitrte mesurement) in 29, 21, 211, 212, nd 213 for 18 fields. The blck verticl line indictes the threshold vlue for the residul nitrte in Flnders (9 kg NO 3- -N h -1 ). The horizontl dotted lines indicte tht for residul nitrte content of 9 kg NO3-N h -1, the nitrte concentrtion t the bottom of the root zone over the winter period vries between 7 nd 16 mg NO 3- /L. 31

313 number of monitoring well-field combintions Vrition of the process fctor for groundwter The trvel times of the 18 wells rnged between.5 nd 4.2 yers, hving n verge of 2. yers. The PF vried between.34 nd 198, hving n verge of 235. The vlue.34 is n outlier, nd other vlues strt from round 1, s it should be. A PF equl to 1 mens tht no dilution nd denitrifiction occurs. A vlue smller thn one would men the nitrte concentrtion increse s the wter (nd nitrte) moves through vdose nd sturted zone to the monitoring well, which is impossible. On liner scle, the PF shows very skewed distribution (grph not shown). When bin limits re defined in ccordnce with log scle, the histogrm shows n irregulr bimodl distribution (Figure 24). Wells for which PF>5 re presumbly wells where strong reducing conditions occur nd lmost ll the nitrte is removed by denitrifiction < >934 Process fctor (PF) for groundwter Figure 24: Histogrm of the PF observed for the 18 plots with mtching residul nitrte contents nd nitrte concentrtions in the groundwter monitoring well. Boundries for the bins were defined in ccordnce with the observtion tht ssuming PF vries over logrithmic scle. The cumultive distribution of the observed PF vlues (Figure 241) indictes tht 14 % of the fields hd PF<1.4, the vlue t lest needed to ensure tht ll fields result in nitrte concentrtion in the groundwter smller thn the EU threshold of 5 mg NO - 3 /L provided the residul nitrte content remins below 9 kg NO - 3 -N/h (see section ). Twenty-five % of the fields hd PF<

314 % of fields with PF < given vlue The distribution is similrly shped s the distribution observed by Vn Overtveld et l. (29) (gry dots in Figure 241), except tht there re fewer wells with PF smller thn 1, which is presumbly becuse in the present study the nitrte residue ws lwys mesured, while in the previous study it ws in most cses estimted, thus creting more vrition in PF vlues (nd wider distribution) nd more vlues below one. A vlue below one is presumbly n rtefct occurring when residul nitrte content in the soil nd hence the soil solution nitrte concentrtion t the bottom of the root zone is underestimted. The new distribution is lso shifted to the right (Figure 241). 1% 9% 8% 7% 6% 5% 4% 3% 2% 1% % Process fctor (PF) Figure 241: Cumultive distribution of the PF observed for the 11 plots with mtching residul nitrte contents nd nitrte concentrtions in the groundwter monitoring well (blue symbols). For comprison the distribution observed by Vn Overtveld et l. (29) for 525 monitoring wells is lso shown (gry symbols). The blck lines verticl indicte the % of fields with pf< 1.4 nd pf<3.2. A mp showing the sptil distribution of the PF in Flnders (Figure 242) shows tht the PF is highly vrible in spce nd does not show cler sptil pttern. This ws lredy observed in the study by Vn Overtveld et l. (211) (Figure 243). 312

315 Figure 242: Sptil distribution of the PF groundwter (vlue shown with color code) observed for the 18 plots with mtching residul nitrte contents nd nitrte concentrtions in the groundwter monitoring well. For comprison we used the sme bin boundries s in the study by Vn Overtveld (29, p. 112). The hydrogeologiclly homogeneous zones in Flnders re shown s bckground colors. Figure 243: Sptil distribution of the PF groundwter (vlue shown with color code) observed for the 525 monitoring wells in the study by Vn Overtveld (29, p. 112). The hydrogeologiclly homogeneous zones in Flnders re shown s bckground colors. 313

316 15 Conclusion Comprble to the results of (Vndervelpen et l., 211), derogtion did not led to sttisticl significnt differences in nutrients, nor in soil nor in wter. In the monitoring network soil nd wter smples were tken t different times (from utumn 211 until utumn 214). The most importnt prmeters nlysed on these smples re nitrogen nd phosphorous. For both types of smples (soil nd wter), no sttisticlly significnt differences could be found between derogtion nd no derogtion prcels. No sttisticl differences were observed for leched mount of nutrients during winter between derogtion nd no derogtion prcels. In generl, derogtion prcels re chrcterized by higher levels of fertilistion by orgnic nd minerl fertilisers. Moreover, the mount of nutrients exported on derogtion prcels re on higher levels, minly by the export of n extr cut of grsslnd. This higher yield is the reson why higher levels of fertilistion do not result in higher nitrte residue levels or higher concentrtions of phosphorous nd nitrte-n in surfce wter nd groundwter originting from derogtion prcels. Even for long term derogtion nd no-derogtion prcels no sttisticl significnt differences re found. Linking prcel chrcteristics nd the resulting wter smples, showed no sttisticl difference between derogtion nd no derogtion prcels. The process fctor ws evluted for the prcels of the network, when monitoring well or MAP smpling point ws present. It is confirmed gin tht the process fctor groundwter is highly vrible without cler sptil pttern. Bsed on this extensive network of prcels nd the vriety of mesurements on prcels nd in the wter, derogtion in Flnders hs no negtive impct on the wter qulity. 314

317 References Beckers, V., Jcxsens, P., Deproost, P., Vn Meirvenne, M., Vn Orshoven, J. (211). AARDEWERK Vlnderen - 21: The revised nd extended dtmodel nd dtbse for preserving the Belgin soil survey dt. Book of bstrcts of Themtic Dy 211 of the Soil Science Society of Belgium. Themtic Dy 211 of the Soil Science Society of Belgium. Brussels, Belgium, 7 December 211, Boon, W. (1984). Onderzoek nr het verbnd tussen het koolstofpercentge en de volumedichtheid vn de grond. Intern Rpport Bodemkundige Dienst vn België, Heverlee. Burns, I. G. (1974). A model for predicting the redistribution of slts pplied to fllow soils fter excess rinfll or evportion. Journl of Soil Science 25, Coppens, G., Vndendriessche, H., Moens, W., Bries, J. (29).De mestwegwijzer: overzicht vn 15 jr mestnlyse door de Bodemkundige Dienst vn België. Bodemkundige Dienst vn België, Heverlee. Geypens M., Vndendriessche H. en Bries J. (1994). Experience with nitrogen N-INDEX expert system: powerful tool in nitrogen recommendtion. Communictions in Soil Science nd Plnt Anlysis, 25(9&1), p Herelixk E., Vogels N., Vnongevl L., Geypens M., Oorts K., Rombuts S., Smmels L.,Verstreten W.W., El-Sdek A., Feyen, J., Coppens F., Merckx R., D Hene K., Moreels E., De Neve S., Slomez J., Boeckx P., Hofmn G., Vn Cleemput O., Librecht I., Wellens, J. en Vn Orshoven J. (22). Bepling vn de hoeveelheid minerle stikstof in de bodem ls beleidsinstrument. Studie uitgevoerd in opdrcht vn de Vlmse Lndmtschppij. Jury, W.A., Horton, R., 24. Soil physics. 6th Edition. John Wiley nd Sons, Inc., New York, 37 pp. KMI. Mes S., Elsen A., Tits M., Boon W., Deckers S., Bries J., Vogels N. en Vndendriessche H. (212). Wegwijs in de bodemvruchtbrheid vn de Belgische kkerbouw- en weilndpercelen (28-211). Bodemkundige Dienst vn België, Heverlee. 198 p. 315

318 Peeters, L., Fsbender, D., Bteln, O., Dssrgues, A., 21. Byesin dt fusion for wter tble interpoltion: Incorporting hydrogeologicl conceptul model in kriging. Wter Resources Reserch 46, W8532. Rwls, W.J., Estimting Soil Bulk-Density from Prticle-Size Anlysis nd Orgnic-Mtter Content. Soil Science 135, Schouwmns, O. (24). Inventristie vn de fosftverzdiging vn lndbouwgronden in Nederlnd. Wgeningen, Alterr, Alterr-rpport pp. Toride, N., Leij, F.J., vn Genuchten, M.T., A Comprehensive Set of Anlyticl Solutions for Nonequilibrium Solute Trnsport with 1st-Order Decy nd Zero-Order Production. Wter Resources Reserch 29, Toride, N., Leij, F.J., vn Genuchten, M.T., The CXTFIT Code for Estimting Trnsport Prmeters from Lbortory or Field Trcer Experiments. Version 2.. Reserch Report No. 137, 121 p., U.S. Slinity Lbortory, USDA, ARS, Riverside, Cliforni, USA. Vn der Zee S.E.A.T.M, Vn Riemsdijk W.H., De Hn F.A.M. (199). Het protokol fosftverzdigde gronden. Deel 1. Toeliching. Vkgroep Bodemkunde en Plntenvoeding, Lndbouwuniversiteit Wgeningen. Vn der Zee S.E.A.T.M, Vn Riemsdijk W.H., De Hn F.A.M. (199b). Het protokol fosftverzdigde gronden. Deel 2. Technische uitwerking. Vkgroep Bodemkunde en Plntenvoeding, Lndbouwuniversiteit Wgeningen. Vndervelpen, D., Vn Overtveld, K., Tits, M., Peeters, L., Elsen, A., Bries J., Bteln, O., Vn Orshoven, J., Vnderborght, J., Diels, J., Vndendriessche, H. (211) Estblishment nd follow-up of monitoring network of frms to ssess the impct of derogtion on the wter qulity. Study crried out under the uthority of the Flemish Lnd Agency by the Soil Service of Belgium nd the Deprtment of Erth nd Environmentl Science (K.U.Leuven). c. 24 pp. Vn De Vreken, P., Vn Holm, L., Diels, J., Vn Orshoven, J., 29. Bodemverdichting in Vlnderen en fbkening vn risicogebieden voor bodemverdichting: Eindrpport vn een verkennende studie in opdrcht vn de Vlmse Overheid, Deprtement Leefmilieu, Ntuur, Energie, Afdeling Lnd en Bodembescherming, Ondergrond, Ntuurlijke Rijkdommen. K.U.Leuven, Sptil Applictions Division en Afdeling Bodem en Wter, 126 pp. 316

319 Vn Opstl M., Tits M., Beckers V., Elsen A., Vn Overtveld K., Bteln O., Vn Orshoven J., Bries, J., Vndendriessche, H., Diels, J. (214). Vernieuwde kwntificering vn de verliezen vn N en P vnuit de lndbouw nr het oppervlktewter. Eindrpport, mei 214. Studie uitgevoerd in opdrcht vn de Vlmse Milieumtschppij door het Deprtement Ard- en Omgevingswetenschppen (KU Leuven) en de Bodemkundige Dienst vn België. 318 pp. Vn Orshoven, J., Deckers, J.A., Vndenbroucke, D., Feyen, J., The completed dtbse of Belgin soil profile dt nd its pplicbility in plnning nd mngement of rurl lnd. Bulletin des Recherches Agronomiques de Gembloux 28, Vn Overtveld, K., Tits, M., Vn De Vreken, P., Vndervelpen, D., Peeters, L., Bteln, O., Vn Orshoven, J., Vnderborght, J., Elsen, A., Bries, J., Vndendriessche, H., Kuhr, P., Wendlnd, F., Diels, J., 211. Beplen vn procesfctoren voor oppervlktewter en grondwter ter evlutie vn de nitrtstikstofresidu-norm. Eindrpport fse 2 en fse 3. Studie uitgevoerd in opdrcht vn de Vlmse Lndmtschppij door het Deprtement Ard- en Omgevingswetenschppen (K.U.Leuven), de Bodemkundige Dienst vn België en het Agrosphere Institute, Forschungszentrum Jülich., 216 pp. Wgeningen UR (25). Mest- en minerlenkennis voor de prktijk. Teelt en stikstof-effect vn groenbemesters. Plntrdig Bld 18. Weynnts, M., Vereecken, H., Jvux, M., 29. Revisiting Vereecken Pedotrnsfer Functions: Introducing Closed-Form Hydrulic Model. Vdose Zone Journl 8,

320 Annex 1 Tble 18: Different soil fertility clsses for ph-kcl for rble lnd for different soil textures (only vlid with norml crbon levels). Clss ph-kcl Snd ph-kcl Sndy-lom ph-kcl Lom ph-kcl Polder Strongly cid < 4. < 4.5 < 5. < 5.5 Low Rther low Optiml level Rther high High Very high > 6.8 > 7.4 > 8. > 8.1 Tble 19: Different soil fertility clsses for ph-kcl for grsslnd for different soil textures (only vlid with norml crbon levels). Clss ph-kcl Snd ph-kcl Sndy lom - lom ph-kcl Polder Strongly cid < 4.4 < 4.6 < 4.9 Low Rther low Optiml level Rther high High Very high > 6.4 > 7. > 7.2 Tble 11: Different soil fertility clsses for percentge crbon for rble lnd for different soil textures. Clss %C Snd %C Sndy lom-lom %C Polder Very low < 1.2 <.8 < 1. Low Rther low Optiml level Rther high High Pety > 1. > 7. >

321 Tble 111: Different soil fertility clsses for percentge crbon for grsslnd for different soil textures. Clss %C All soil textures, except lom Very low < 2. Low Rther low Optiml level Rther high High Pety > 1. %C Lom < > 9. Tble 112: Different soil fertility clsses for phosphorus for rble lnd (only vlid for soils with specific grvity of 1.3). Clss Very low Low Rther low Optiml level Rther high High Very high mg P/1 g dry soil (A.L.-extrct) ll soil textures < > 5 Tble 113: Different soil fertility clsses for phosphorus for grsslnd (only vlid for soils with specific grvity of 1.3). Clss Very low Low Rther low Optiml level Rther high High Very high mg P/1 g dry soil (A.L.-extrct) ll soil textures < > 6 319

322 Tble 114: Different soil fertility clsses for K for rble lnd for different soil textures (only vlid for soils with specific grvity of 1.3).Tble 115: Different soil fertility clsses for K for rble lnd for different soil textures (only vlid for soils with specific grvity of 1.3). Clss Very low Low Rther low Optiml level Rther high High Very high mg K/1 g dry soil (A.L.-extrct) Snd < > 5 mg K/1 g dry soil (A.L.-extrct) Sndy lom-lom < > 6 mg K/1 g dry soil (A.L.-extrct) Polder < > 7 Tble 116: Different soil fertility clsses for K for grsslnd for different soil textures (only vlid for soils with specific grvity of 1.6). Clss Very low Low Rther low Optiml level Rther high High Very high mg K/1 g dry soil (A.L.-extrct) All soil textures except polder < > 45 mg K/1 g dry soil (A.L.-extrct) Polder < > 5 Tble 117: Different soil fertility clsses for Mg for rble lnd for different soil textures (only vlid for soils with specific grvity of 1.6). Clss Very low Low Rther low Optiml level Rther high High Very high mg Mg/1 g dry soil (A.L.-extrct) Snd < > 25 mg Mg/1 g dry soil (A.L.-extrct) Sndy lom-lom < > 3 mg Mg/1 g dry soil (A.L.-extrct) Polder < > 45 32

323 Tble 118: Different soil fertility clsses for Mg for grsslnd for different soil textures (only vlid for soils with specific grvity of 1.6). Clss Very low Low Rther low Optiml level Rther high High Very high mg Mg/1 g dry soil (A.L.-extrct) Snd < > 35 mg Mg/1 g dry soil (A.L.-extrct) Sndy lom-lom < > 4 mg Mg/1 g dry soil (A.L.-extrct) Polder < > 48 Tble 119: Different soil fertility clsses for C for rble lnd for different soil textures (only vlid for soils with specific grvity of 1.3). Clss Very low Low Rther low Optiml level Rther high High Very high mg C/1 g dry soil (A.L.-extrct) Snd < > 26 mg C/1 g dry soil (A.L.-extrct) Sndy lom < > 45 mg C/1 g dry soil (A.L.-extrct) Lom < > 1 mg C/1 g dry soil (A.L.-extrct) Polder < > 1 Tble 12: Different soil fertility clsses for C for grsslnd for different soil textures. (only vlid for soils with specific grvity of 1.6). Clss Very low Low Rther low Optiml level Rther high High Very high mg C/1 g dry soil (A.L.-extrct) Snd < > 26 mg C/1 g dry soil (A.L.-extrct) Sndy lom < > 5 mg C/1 g dry soil (A.L.-extrct) Lom < > 1 mg C/1 g dry soil (A.L.-extrct) Polder < > 1 321

324 Tble 121: Different soil fertility clsses for N for rble lnd (only vlid for soil textures with specific grvity of 1.3). Clss Very low Low Rther low Optiml level Rther high High Very high mg N/1 g dry soil (A.L.-extrct) ll soil textures < > 2. Tble 122: Different soil fertility clsses for N for grsslnd (only vlid for soil textures with specific grvity of 1.6). Clss Very low Low Rther low Optiml level Rther high High Very high mg N/1 g dry soil (A.L.-extrct) ll soil textures < >

325 Annex 2 Exmple of stndrd soil nlysis with liming nd fertilistion dvice for the 3 next growing sesons. 323

326 324

327 325

328 326

329 Annex 3 Since wether nd climte conditions influence strongly the processes in soil, like minerlistion, leching, crop growth, n overview is given of climte conditions in the yers , the time period covered by this project. The vlues, figures nd tbles shown re observtions t Brussels- Ukkel, gthered by the Royl Meteorologicl Institute. The norml vlues of the different prmeters, re the verge vlues of the prmeters in the period This period of 3 yers is chosen s the ltest reference period to determine the norml vlues of Ukkel. The degree of bnormlity of vlues is bsed on the reference period It needs to be noticed tht the figures nd vlues shown below re observtions t Brussels-Ukkel s mentioned before. For clcultions t individul prcels for exmple of leching (Burns) the weighed verge of rinfll nd ET of the 3 closest wether sttions is tken into ccount s mentioned before in prgrph Climte 211 The yer 211 ws the wrmest yer t Brussels-Ukkel, ever since the strt of the continuous meteorologicl observtions in In utumn 211 (defined in meteorologicl terms s period September-November), the number of dys with rinfll ws most exceptionl smll. Only 37 dys with precipittion compred to norml vlue of 51 dys. Also the totl mount of rinfll ws exceptionl low, 14.4 mm compred to mm s norml vlue in the period (Figure 244). Most prominent ws November 211. The lowest mount of rinfll ever ws mesured, 8.5 mm. Besides the minor rinfll, the bundnce of sunshine ws remrkble (Figure 246). Autumn 211 ws the fifth most sunniest utumn since 1887, 45 h (norml vlue: 322 h). At lst utumn 211 ws lso exceptionl wrm (Figure 245). The verge temperture ws 12.4 C, compred to 1.9 C s norml vlue. December however ws lso wrm but rinfll ws high. The higher tempertures, the lck of rin nd longer period with sunshine in November 211, explin the negtive vlues for the wter blnce in November 211 shown in Tble

330 Temperture ( C) Rinfll (mm) Month Figure 244: Evolution of rinfll (mm) t Ukkel in 211 (pink curve), indiction of monthly norml vlues (red curve), indiction of highest nd lowest vlues ever mesured t Ukkel since 1833 (ends of blue columns with indiction of the record yer). (Source: KMI, Month Figure 245: Evolution of temperture ( C) t Ukkel in 211 (pink curve), indiction of monthly norml vlues (red curve), indiction of highest nd lowest vlues ever mesured t Ukkel since 1833 (ends of blue columns with indiction of the record yer). (Source: KMI, 328

331 Sunshine (hours) Month Figure 246: Evolution of monthly sunshine (hours) t Ukkel in 211 (pink curve), indiction of monthly norml vlues (red curve), indiction of highest nd lowest vlues ever mesured t Ukkel since 1887 (ends of blue columns with indiction of the record yer). (Source: KMI, Climte 212 Bse on meteorologicl dt the yer 212 ws reltively norml. However rinfll ws highly vrible round the norml vlues. In December rinfll ws very high nd new record ws estblished (Figure 247). In August it ws very dry nd in October it ws more riny s usul. In October 211 wter blnce showed high positive vlues (Tble 75). The verge temperture ech month ws lwys ner the norml vlues except in Februry when it ws colder thn norml (Figure 248). The number of hours of sunshine per month ws close to the norml vlues. Only in Mrch ws exceptionl sunny. 329

332 Temperture ( C) Rinfll (mm) Month Figure 247: Evolution of rinfll (mm) t Ukkel in 212 (pink curve), indiction of monthly norml vlues (red curve), indiction of highest nd lowest vlues ever mesured t Ukkel since 1833 (ends of blue columns with indiction of the record yer). (Source: KMI, Month Figure 248: Evolution of temperture ( C) t Ukkel in 212 (pink curve), indiction of monthly norml vlues (red curve), indiction of highest nd lowest vlues ever mesured t Ukkel since 1833 (ends of blue columns with indiction of the record yer). (Source: KMI, 33

333 Sunshine (hours) Month Figure 249: Evolution of monthly sunshine (hours) t Ukkel in 212 (pink curve), indiction of monthly norml vlues (red curve), indiction of highest nd lowest vlues ever mesured t Ukkel since 1887 (ends of blue columns with indiction of the record yer). (Source: KMI, Climte 213 In 213 rinfll ws often more limited thn in norml conditions. The difference however ws rther smll. In My, however, rinfll ws bundnt nd more thn the double of norml rinfll ws observed (Figure 25). Until June, verge temperture in 213 ws some lower thn norml. Since ugust temperture ws norml. In December, however, it ws wrmer thn norml nd wrm winter begn (Figure 251). Not only temperture but lso sunshine ws less in the first months of 213 (Figure 252). 331

334 Figure 25: Evolution of rinfll (mm) t Ukkel in 213 (pink curve), indiction of monthly norml vlues (red curve), indiction of highest nd lowest vlues ever mesured t Ukkel since 1833 (ends of blue columns with indiction of the record yer). (Source: KMI). Figure 251: Evolution of temperture ( C) t Ukkel in 213 (pink curve), indiction of monthly norml vlues (red curve), indiction of highest nd lowest vlues ever mesured t Ukkel since 1833 (ends of blue columns with indiction of the record yer). (Source: KMI). 332

335 Figure 252: Evolution of monthly sunshine (hours) t Ukkel in 213 (pink curve), indiction of monthly norml vlues (red curve), indiction of highest nd lowest vlues ever mesured t Ukkel since 1887 (ends of blue columns with indiction of the record yer). (Source: KMI). Climte 214 In 214 longer periods with less or more rinfll s norml were noticed. In spring, Mrch nd April, there ws clerly less rinfll s norml. However in the periode June-August the mount of precipittion ws higher s norml, especilly in August. Autumn 214 ws dryer s norml. As well in September, October nd November the rinfll ws lower s norml but it ws most expceptionl in September. In September 214 there ws only 15.1 mm rinfll t Ukkel compred to 68.9 mm s norml vlue for Ukkel in September. Rinfll in utumn 214 mounted for mm (norml vlue: 219.9), considered s bnorml since such vlue occurs once in 1 yers. Winter ended in Jnury nd Februry with higher temperture s norml. These higher tempertures continued in Mrch nd April. In summer the temperture ws norml but since September temperture ws ech month until November clerly higher s norml. The verge temperture in utumn 214 ws 13 C, compred to 1.9 C s norml vlue. This ws considered s exceptionl since such n verge vlue occurs once in 3 yers. It ws the second wrmest utumn since Sunshine ws lmost norml. In Mrch there ws clerly more sunshine s norml but in August there ws less sunshine s norml. 333

336 Temperture ( C) Rinfll (mm) Month Figure 253: Evolution of rinfll (mm) t Ukkel in 214 (pink curve), indiction of monthly norml vlues (red curve), indiction of highest nd lowest vlues ever mesured t Ukkel since 1833 (ends of blue columns with indiction of the record yer). (Source: KMI, Month Figure 254: Evolution of temperture ( C) t Ukkel in 214 (pink curve), indiction of monthly norml vlues (red curve), indiction of highest nd lowest vlues ever mesured t Ukkel since 1833 (ends of blue columns with indiction of the record yer). (Source: KMI, 334

337 Sunshine (hours) Month Figure 255: Evolution of monthly sunshine (hours) t Ukkel in 214 (pink curve), indiction of monthly norml vlues (red curve), indiction of highest nd lowest vlues ever mesured t Ukkel since 1887 (ends of blue columns with indiction of the record yer). (Source: KMI, In Figure 256 ll utumns t Ukkel since 196 re positioned regrding rinfll, temperture nd sunshine. Rinfll nd temperture re compred to the norml vlues observed in the period It cn be seen tht utumn 211 nd 214 re more or less comprble. 335

338 Averge temperture: devition to norml vlue 13,2 C ( ) ( C) Rinfll nd temperture-autumn in Ukkel since 196 to 214 W r m C o l d Dry Dimensionsof spheres re proportionl to time of sunshine Wet Rinfll: rtio to norml vlue ( ) 219,9 mm (%) Figure 256: Position of utumns t Ukkel since 196 to 214 regrding to rinfll, temperture nd sunshine compred to norml vlues of temperture (13.2 C) nd rinfll (219.9 mm) (period ) (Source: KMI, 336