Using nitrogen fertiliser to decrease phosphorus loss from high phosphorus soils

Transcription

1 121 Using nitrogen fertiliser to decrese phosphorus loss from high phosphorus soils R.J. DODD 1,2, R.W. McDOWELL 1,2 nd L.M. CONDRON 2 1 AgReserch Ltd, Invermy Agriculturl Centre, Privte Bg 50034, Mosgiel 9053, New Zelnd. 2 Fculty of Agriculture nd Life Sciences, PO Box 84, Lincoln University, Lincoln 7647, Christchurch, New Zelnd richrd.mcdowell@greserch.co.nz Astrct Decline in soil phosphorus (P) concentrtions is slow, nd environmentlly significnt concentrtions of P cn e lost to wter long fter fertiliser ppliction is decresed. One potentil method to ccelerte the decline in soil P concentrtions is to increse plnt uptke y pplying nitrogen (N). A one-yer lysimeter tril investigted P losses to lechte on three soil types receiving three rtes of N fertiliser (0, 150 nd 300 kg N/h/yr) nd zero or hlf mintennce P fertiliser, with regulr cutting nd removl of psture. Incresing N input incresed nnul psture yield nd decresed DRP loss in lechte compred to the zero N tretment, without incresing nitrte or mmonium loss. Furthermore, tretments receiving hlf mintennce P t ll N rtes hd lower P losses thn the zero N nd zero P tretment. Bsed on cut nd crry system, incresing N fertiliser in conjunction with decresing P fertiliser hs potentil s mitigtion strtegy to decrese P loss without compromising yields or incresing N leching. Introduction Long-term ppliction of phosphorus (P) fertilisers in excess of the crop requirements cn result in uildup of soil P, which in turn hs n incresed potentil for P loss which my impir surfce wter qulity (Shrpley et l. 1994). This, coupled to the rpid increse in the world popultion nd concerns over future P vilility (Gilert 2009), clerly indicte tht more sustinle nd P efficient frming prctices re required. In P-rich soils, one simple method to decrese soil P concentrtions nd P loss would e to stop pplying P fertilisers. However, the decline in soil P following hlt to P fertilisers hs een shown to e very slow (McCollum 1991; Dodd et l. 2012). It is therefore likely tht there will e long lg times, in the scle of decdes or more, etween the cesstion of P fertiliser ppliction to high P soils nd improvements in surfce wter qulity. An dditionl importnt considertion is the effect tht withholding P fertiliser will hve on frm production. Gillinghm et l. (1990) found tht withholding P fertilisers for 4 yers on New Zelnd sheep grzed grsslnd led to 10% reduction in psture dry mtter (DM) production, despite the Olsen P concentrtion remining within the gronomic optimum rnge of mg/kg for sh nd sedimentry soils in New Zelnd sheep nd eef pstures (Morton & Roerts 1999). Furthermore, Dodd et l. (2012) found tht the rte of decline in DM yield following cesstion of P fertiliser to New Zelnd sheep psture ws more closely linked to the rte of decrese in wter-extrctle P (WEP), n indictor of the potentil P loss to overlnd flow, thn to Olsen P. This suggests tht withholding P fertiliser with the im of decresing P loss is likely to led to reduction in production. One potentil strtegy to decrese P loss from high P soils without compromising frm profitility is the cesstion or decrese in P fertiliser pplictions while mintining psture production with N inputs. In mixed grss/clover pstures plnt growth is generlly N-limited, nd this will e especilly true for soils with high P concentrtions. Incresed ppliction of N fertiliser to N-limited soils will increse psture growth leding to incresed plnt uptke of P, effectively mining P from the soil. Perring et l. (2009) modelled the response of soil P concentrtions to incresed dditions of N nd suggested tht short term N fertilistion cn decrese residul fertiliser P stored within the soil in N-limited systems. McDowell & Monghn (2002) lso showed tht incresed rtes of N fertiliser ppliction to New Zelnd grsslnd soil cused significnt decrese in Olsen P nd the totl inorgnic P frction. Pot trils hve shown tht the environmentlly importnt soil P forms, wter extrctle P (WEP) nd clcium chloride extrctle P (CCl 2 -P), cn e drmticlly decresed with N fertiliser ppliction nd regulr cutting (Koopmns et l. 2004). We propose tht pplying cut nd crry system to criticl source res in ctchment, with high soil P concentrtions nd high risk of P loss, long with the ppliction of nitrogen over short period of 1 yer could significntly decrese P loss in the longterm. However, there hs een little direct mesurement of P loss to wter following the implementtion of this strtegy. Furthermore it is importnt to investigte the effect of dditionl N pplictions on N losses. This study imed to investigte the effect of

2 122 Proceedings of the New Zelnd Grsslnd Assocition 74: (2012) the following fertiliser regimes on P nd N loss to susurfce lechte through lysimeter tril. We tested the hypothesis tht the ddition of incresed N fertiliser, coupled with cesstion or decrese in P fertiliser, will decrese susurfce P loss, y pplying zero, 150 or 300 kg N/h/yr nd zero or hlf mintennce P to three pstorl soils nd mesuring N nd P loss to susurfce lechte nd psture production under cut nd crry regime. Methods Lysimeter core collection Grzed psture sites were selected on Allophnic, Brown nd Pumice soil orders (New Zelnd Soil Clssifiction, Hewitt 2010) with similr initil topsoil Olsen P concentrtions, mesured from five replicte 0 75 mm cores tken t ech site (Tle 1). The psture ws mixture of ryegrss nd clover. Twenty-four shllow lysimeter cores (22 cm deep y 16 cm dimeter) were tken of ech soil y crefully excvting round the soil core nd gently lowering PVC pipe. When the pipe ws completely lowered, the soil eneth ws cut with knife to ensure clen rek. The soil cores were trnsported to the Invermy Agriculturl Centre in Mosgiel, nd n end cp, filled with cid-wshed silic snd, ws ttched to the se of ech lysimeter. Petroleum jelly ws used to sel the gp etween the edge of the soil core nd the PVC pipe to prevent edgeflow. An outlet hole in the end cp llowed collection of the lechte. The ssemled lysimeters were then put Tle 1. Loction of field sites from which the lysimeters were tken, the soil type nd New Zelnd Soil Clssifiction soil order nd the men initil Olsen P concentrtion of soil smples tken t the time of lysimeter collection t 0 75 mm depth. Vlues given in prentheses show one stndrd error of the mesurement. Smpling loction Rukur Reserch Centre, est of Hmilton, Wikto Woodlnd Reserch Sttion, est of Invercrgill, Southlnd Rerewhkitu Frm, south of Rotru, By of Plenty Soil type (NZ soil clssifiction) Horotui silt lom (Typic Orthic Allophnic Soil) Wikiwi silt lom (Typic Firm Brown Soil) Tupo sndy lom (Immture Orthic Pumice Soil) Men initil Olsen P concentrtion (0-75 mm depth) (mg P/kg) (+/- 2.09) (+/- 2.60) (+/- 5.49) Tle 2. Nitrte-N nd mmonium-n concentrtions in lechte nd loss per lysimeter. The lest significnt difference t the P<0.05 level of significnce is given for the comprison of soil order y tretment men concentrtions. Men loss (mg/lys/yr) Men concentrtion (mg/l/yr) Soil Tretment NH 4 -N NO 3 -N NH 4 -N NO 3 -N Allophnic 0N & 0P N & ½ mintennce P kg N/h/yr & 0P kg N/h/yr & ½ mintennce P kg N/h/yr & ½ mintennce P kg N/h/yr & 0P Brown 0N & 0P N & ½ mintennce P kg N/h/yr & 0P kg N/h/yr & ½ mintennce P kg N/h/yr & 0P kg N/h/yr & ½ mintennce P Pumice 0N & 0P N & ½ mintennce P kg N/h/yr & 0P kg N/h/yr & ½ mintennce P kg N/h/yr & 0P kg N/h/yr & ½ mintennce P LSD 05 soil x trt

3 Using nitrogen fertiliser to decrese phosphorus loss from high... (R.J. Dodd, R.W. McDowell nd L.M. Condron) 123 Dry mtter (g/lysimeter) N & 0P 0N & 1/2P 150N & 0P 150N & 1/2P 300N & 0P 300N & 1/2P c d c c c DRP loss (mg P/lysimeter/yr) ) DRP loss 0N & 0P 0N & 1/2P 150N & 0P 150N & 1/2P 300N & 0P 300N & 1/2P Allophnic Brown Pumice 0.5 ) DOP loss Figure 1. Men totl psture DM yield from ech lysimeter. The letters denote differences etween tretments within ech soil order t the P<0.05 level of significnce determined vi Duncn s Multiple Rnge Test. Arevitions; 0N & 0P = zero N nd zero P fertiliser pplied, 0N & 1/2P = zero N nd hlf mintennce P ppliction, 150N & 0P = 150 kg N/h/yr nd zero P ppliction, 150N & 1/2P = 150 kg N/h/yr nd hlf mintennce P ppliction, 300N & 0P = 300kg N/h/yr nd zero P ppliction nd 300N & 1/2P = 300 kg N/h/yr nd hlf mintennce P ppliction. in plce in dedicted outdoor fcility, comprising n elevted nk of soil into which the lysimeters were set llowing dringe into collection ottles elow. Study conditions nd lechte collection. The 1-yer tril commenced in Ferury 2011, nd during this time there ws totl of 600 mm of rinfll. To supplement rinfll over the drier summer months irrigtion ws pplied to the lysimeters fortnightly, t depth of 12.5 mm during Ferury nd Mrch 2011 nd from Decemer to Ferury Nitrogen ws pplied s ure t three rtes, 0, 150 nd 300 kg N/h/yr, in split pplictions of 30 nd 60 kg/h/ yr cross the grss growing seson. Phosphorus ws pplied s superphosphte t two rtes, zero nd hlf mintennce P, in one ppliction t the strt of the tril. The hlf mintennce ppliction corresponded to n ppliction rte of 17, 14 nd 19 kg P/h/yr for the Allophnic, Brown nd Pumice soils respectively. In ddition, mintennce ppliction of sulphur (S) nd potssium (K), tking into ccount the S supplied y superphosphte, ws pplied to ech of the lysimeters t the strt of the tril, s potssium sulphte nd potssium chloride t n ppliction rte of 38, 32 nd 42 kg K/h/yr nd 3, 11 nd 10 kg S/h/yr for the Allophnic, Brown nd Pumice soils respectively. Psture ws cut every 30 dys during the grss growing seson. The clippings were removed nd psture DM determined. Lechte smples were collected under vcuum the dy following ech rinfll event. If the volume collected ws less thn 1L the lechte ws frozen DOP loss (mg P/lysimeter/yr) Allophnic Brown Pumice Figure 2: 2. Men totl Men ) DRP totl loss ) ) DOP DRP loss loss in lechte ) DOP from the loss lysimeters. in lechte The letters denote differences from etween the tretments lysimeters. within ech The soil letters order t denote the P<0.05 differences level of significnce determined etween y Duncn s tretments Multiple Rnge within Test. ech soil order t Arevitions; DRP = the Dissolved P<0.05 rective P, level DOP = Dissolved of significnce orgnic P, 0N & 0P determined = zero N nd zero P y fertiliser pplied, 0N & 1/2P = Duncn s zero N nd hlf Multiple mintennce P Rnge ppliction, Test. 150N & 0P = 150 kg N/h/yr nd zero P ppliction, 150N & 1/2P = 150 kg N/h/yr nd hlf mintennce P ppliction, 300N & 0P = 300kg N/h/yr Arevitions; DRP = Dissolved rective P, DOP = Dissolved nd zero P ppliction orgnic nd 300N P, & 1/2P 0N & = 300 0P kg = N/h/yr zero N nd nd hlf mintennce zero P fertiliser P ppliction. pplied, 0N & 1/2P = zero N nd hlf mintennce P ppliction, 150N & 0P = 150 kg N/h/yr nd zero P ppliction, 150N & 1/2P = 150 kg N/h/yr nd hlf mintennce P ppliction, 300N & 0P = 300kg N/h/yr nd zero P ppliction nd 300N & 1/2P = 300 kg N/h/yr nd hlf mintennce P ppliction. nd ulked together with susequent events, to rech 1L cumultive totl, to minimise nlyticl demnd. Lechte smples were immeditely filtered through 0.45 µm memrne nd stored elow 4 C efore nlysis the following dy. Lechte nlysis Filtered lechte smples were nlysed for dissolved rective P (DRP) nd totl dissolved P (TDP), fter cid persulphte digestions (Rowlnd & Hygrth 1997), using the molydte lue method of Wtne & Olsen (1965). Dissolved orgnic phosphorus ws clculted s the difference etween TDP nd DRP. For the first 2 months of the tril, nitrte nd mmonium concentrtions were determined using YSI Professionl Plus multi-prmeter meter with ion selective electrodes, clirted with flow injection nlysis (FIA) of selected smples. Therefter, concentrtions were determined vi FIA. Sttisticl nlyses A design with three soil orders nd six different fertiliser

4 124 Proceedings of the New Zelnd Grsslnd Assocition 74: (2012) tretments, three rtes of N or P fertiliser nd four replictes ws used s sttisticl model. The nutrient loss in the collected lechte nd totl DM yield were sujected to two-wy nlysis of vrince. Specific comprisons were mde with the lest significnt difference t P<0.05 (LSD 05 ). All sttisticl nlyses were crried out using the sttisticl pckge GenStt (GenStt Committee 2010). Results nd Discussion Over the course of the tril there were 14 smplings, evenly spced throughout the yer. Appliction of N fertiliser led to significnt increse in psture DM production (P <0.01) cross ll soil types, while ppliction of hlf mintennce P fertiliser did not led to significnt increse in production. This indictes tht nitrogen ws the limiting nutrient (Fig. 1). The increse in production ws ccompnied y significnt decrese in the mount of lechte collected (P<0.001) cross ll three soil orders nd, for the Brown (P = 0.033) nd Pumice soil orders, decrese in DRP loss s mg P/lysimeter/yer (P <0.001) (Figure 2) with no significnt difference etween the two ppliction rtes (150 nd 300 kg N/h/yr). The Allophnic soil order ppered to show decrese in DRP loss, ut this ws not significnt (P>0.05). Interestingly, for the Brown nd Pumice soil orders, ppliction of hlf mintennce P to the lysimeters receiving zero N ppliction, significntly decresed DRP loss compred to the zero N - zero P tretment (Figure 2). Furthermore, this decrese ws of similr mgnitude to tht following the ppliction of N. The resons for the decrese in P loss following low rte of P ppliction re uncler. While there ws no significnt difference in psture DM etween the zero P nd hlf mintennce P pplictions (Fig. 1), the ppliction of P my hve incresed primry production nd iotic P demnd leding to P eing sequestered into the microil P pool. Alterntively, the ppliction of P fertiliser my hve influenced the distriution of P within the different soil P pools, potentilly decresing the P vilility for loss. Further work is required to investigte this. There ws no significnt difference in DOP loss cross the different tretments. Furthermore, DOP concentrtion in lechte collected from ll of the lysimeters represented lrge portion of the TDP nd, with the exception of the zero N nd zero P tretments, the DOP loss ws of similr mgnitude to the DRP loss (Figure 2). There is growing recognition tht significnt portion of DOP cn e ioville to lge through enzymtic hydrolysis (Whitton et l. 1991), ut tht the proportion of ioville DOP in lechte cn e highly vrile (McDowell & Koopmns 2006; Toor et l. 2003). Further work to chrcterise the DOP frction in the lechte from the lysimeters is required to fully ssess the effectiveness of the proposed strtegy of incresing N dditions to decrese P loss. There ws no significnt difference in the nnul nitrte or mmonium loss s mg N/lysimeter/yr cross ll of the soil orders, nd no spike in N loss ws oserved following the ppliction of 150 or 300 kg N/h/yr compred to the zero N tretments (Tle 2). There ws significnt increse in men nitrte concentrtion collected in lechte from the Allophnic lysimeters receiving 300 kg N/h/yr compred to those receiving 0 or 150 kg N/h/yr, however due to decrese in the mount of lechte drining from the 300 kg N/h/yr tretment, presumly due to incresed evpotrnspirtion s result of incresed psture growth, this did not trnslte to n increse in nitrte loss. These results suggest tht, sed on cut nd crry system, the ppliction of N fertiliser does not increse N loss. Hence, further work is required to determine if the lrge N inputs from urine ptches hve similr effect on P loss s lower rtes of N vi ure. Conclusions The ppliction of incresed rtes of N fertiliser to the Brown nd Pumice soil orders decresed P loss in lechte, lrgely s DRP, nd incresed psture DM compred to soils receiving zero N. There ws no effect on nitrte or mmonium loss. No significnt tretment effect ws oserved for the Allophnic soil order, nd the ppliction of incresed nitrogen led to n increse in nitrte concentrtion in the lechte, ut not n increse in nitrte loss s mg N/lysimeter/yr. This study demonstrtes the potentil of incresing N fertilisers s strtegy to decrese P loss from high P soils within short timefrme while mintining yields when sed on cut nd crry system for Brown nd Pumice soil orders ut suggests tht the strtegy my not e suitle for Allophnic soil orders. Following the reduction in soil P concentrtions, grzing cn resume on this psture in ccordnce with est mngement prctices. REFERENCES Dodd, R.J.; McDowell, R.W.; Condron, L.M Predicting the chnges in environmentlly nd gronomiclly significnt phosphorus forms following cesstion of phosphorus fertiliser pplictions to grsslnd. Soil Use nd Mngement 28: , GenStt GenStt for Windows. 13th edn. VSN Interntionl Ltd, Oxford, UK. Gilert, N The disppering nutrient. Nture 461:

5 Using nitrogen fertiliser to decrese phosphorus loss from high... (R.J. Dodd, R.W. McDowell nd L.M. Condron) 125 Gillinghm, A.G.; Richrdson, S.; Power, I.L.; Riley, J Long term effects of withholding phosphte ppliction on North Islnd hill country: Whtwht Reserch Centre. Proceedings of the New Zelnd Grsslnd Assocition 51: Hewitt, A.E New Zelnd Soil Clssifiction. Lndcre Reserch Science Series No. 1. 3rd Edition. Koopmns, G.F.; Chrdon, W.J.; Ehlert, P.A.I; Dolfing, J.; Suurs, R.A.A.; Oenem, O.; vn Riemsdijk, W.H Phosphorus vilility for plnt uptke in phosphorus-enriched nonclcreous sndy soil. Journl of Environmentl Qulity 33: McCollum, R.E Buildup nd decline in soil phosphorus: 30-yer trends on Typic Umpruult. Agronomy Journl 83: McDowell, R.W.; Koopmns, G.F Assessing the iovilility of dissolved orgnic phosphorus in psture nd cultivted soils treted with different rtes of nitrogen fertiliser. Soil Biology nd Biochemistry 38: McDowell, R.W.; Monghn, R.M The potentil for phosphorus loss in reltion to nitrogen fertiliser ppliction nd cultivtion. New Zelnd Journl of Agriculturl Reserch 45: Morton, J.D.; Roerts, A.H Fertiliser use on New Zelnd sheep nd eef frms. New Zelnd Fertiliser Mnufcturers Reserch Assocition, Newmrket, New Zelnd. Perring, M.; Edwrds, G.; de Mzncourt, C Removing phosphorus from ecosystems through nitrogen fertiliztion nd cutting with removl of iomss. Ecosystems 12: Rolnd, A.P.; Hygrth, P.M Determintion of totl dissolved phosphorus in soil solutions. Journl of Environmentl Qulity 26: Shrpley, A.N.; Chpr, S.C.; Wedepohl, R.; Sims, J.T.; Dniel, T.C.; Reddy, K.R Mnging griculturl phosphorus for protection of surfce wters: issues nd opinions. Journl of Environmentl Qulity 23: Toor, G.S.; Condron, L.M.; Di, H.J.; Cmeron, K.C.; Cde-Menun, B. J Chrcteriztion of orgnic phosphorus in lechte from grsslnd soils. Soil Biology nd Biochemistry 35: Wtne, F.S.; Olsen, S.R Test of n scoric cid method for determining phosphorus in wter nd NHCO 3 extrcts from soil. Soil Science Society of Americ Proceedings 29: Whitton, B.A.; Gringerm S.L.J.; Hwley, G.R.W.; Simon, J.W Cell-ound nd extrcellulr phosphtse ctivities of cynocteri isoltes. Microil Ecology 21:

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