Weed Suppression with Cover Crops and Undersown Crops in Modern Cropping Systems

Transcription

1 University of Hohenheim Institute for Phytomedicine Deprtment of Weed Science (360) Weed Suppression with Cover Crops nd Undersown Crops in Modern Cropping Systems Disserttion Sumitted in fulfilment of the requirements for the degree Doktor der Agrrwissenschften (Dr.sc.gr. / Ph.D. in Agriculturl Sciences) to the Fculty of Agriculturl Science University of Hohenheim y Jochen Brust Born: 26. April 1983 in Stuttgrt-Bd Cnnsttt, Germny Decemer 2014

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3 This thesis ws ccepted s doctorl disserttion in fulfilment of the requirements for the degree Doktor der Agrrwissenschften (Dr. sc. gr. / Ph. D. in Agriculturl Sciences) y the Fculty of Agriculturl Sciences t University of Hohenheim on Jnury 23rd, Dte of orl Exmintion: April 16th, 2014 Exmintion Committee: Vice-Den Prof. Dr. M. Rodehutscord Hed of the Committee Prof. Dr. R. T. Vögele Supervisor nd Review Prof. Dr. R. Gerhrds Co-Reviewer Prof. Dr. W. Clupein Additionl Exminer Prof. Dr. E. Kndeler

4 Für Angeliki

5 Contents List of Figures List of Tles Arevitions nd Acronyms III IV V 1 Generl Introduction Actul sitution in Germn griculturl systems Benefits of cover crops Benefits of undersown crops Ojectives of this thesis Pulictions Wrum Untersten und Zwischenfrüchte wieder Bedeutung zur Unkrutregulierung in Europäischen Ackerusystemen ekommen Growth nd weed suppression ility of common nd new cover crops in Germny Lopsided ot (Aven strigos) s new summer nnul cover crop for weed suppression in Centrl Europe Evlution of Three Potentil Cover Crops for Weed Suppression in Centrl Europe Introduction Mterils nd Methods Results nd Discussion Mngement of undersown crops influences their competitiveness with cerels nd weeds Introduction I

6 Contents Mterils nd Methods Results Discussion Generl Discussion Growth of new cover crop species in Centrl Europe Weed suppression y cover crops Requirements for weed suppression y cover crops Weed suppression during vegettion of cover crops Weed suppression fter vegettion of cover crops in erly spring Mngement of undersown crops in cerels Weed suppression y undersown crops Improvement for further reserch Possile topics of further reserch Cover Crops Undersown crops Summry 71 5 Zusmmenfssung 77 Biliogrphy 83 Curriculum Vite 97 Erklärung 99 Dnksgung 101 II

7 List of Figures 1 Soil coverge of cover crops Shoot nd root dry mtter of cover crops Shoot nd root dry mtter s well s the density of weeds in plots of cover crops nd the weedy control Shoot nd root dry mtter of cover crops in pots/plots of forge rpe nd nnul ryegrss nd shoot nd root dry mtter of forge rpe nd nnul ryegrss in pots/plots of cover crops nd the weedy control Dry mtter of undersown crops in the field experiment 2009, nd Dry mtter of cerel crops in the experiments Grin nd strw yield of whet in the field experiment Weed density of Chenopodium lum nd Veronic persic t flg lef stge nd hrvest, in the field experiment Weed density in the field experiment III

8 List of Tles 1 Averge climtic conditions, soil properties nd mount of soil minerl nitrogen in oth experiments Air temperture nd precipittion during the growing sesons nd the 20-yer monthly verge t Hohenheim (Institute of Phytomedicine nd Meiereihof), Ihinger Hof nd Trossin Weed density per squre meter in plots of cover crops nd the weedy control in spring Agronomic detils, culturl prctices nd dtes of oservtions in field- nd pot experiments Tempertures nd rinfll during the growing sesons nd the long-time verge t Hohenheim nd Ihinger Hof Undersown crop dry mtter in the field nd pot experiment IV

9 Arevitions nd Acronyms % Percent = Equlity sign Less thn or equl to C E N Benth. C 4 Css. cm DAP dt. e.g. et l. Fig. g Gertn. h HH IHO Degrees Celsius Degree est/longitude Degree north/ltitude Benthm Plnts with C 4 cron fixtion de Cssini Centimetre Dys fter plnting Decitonne For exmple Et lii (nd others) Figure Grm Gärtner Hectr Hohenheim Ihinger Hof V

10 List of Tles kg Kilogrmm L. Linné Lm. Lmrck L.f. Linneus the Younger ltm. Longtime monthly m Metre m 2 mg MV N N min NO 3 Poir. Schre. scop. SD STD t T 50 T. TR USA Vill. WAP α Squre metre milligrm Men vlue Nitrogen Soil ville minerl nitrogen Nitrte Poiret von Schreer Scopoli Stndrd devition Stndrd devition Ton Time until 50 percent emergence Tle Trossin United Sttes of Americ Villrs Weeks fter plnting Proility VI

11 1 Generl Introduction 1.1 Actul sitution in Germn griculturl systems Sustinility nd the production of high yields re the most importnt purposes of every cropping system. However, the resilience nd yield stility of cropping systems decreses if crop diversity within the cropping system is reduced (Smith et l., 2008). In the lst decde, only smll numer of csh crop species were grown in Germn griculturl systems due to economic constrints nd regionl circumstnces. In 2011, the fll seeded crops winter whet, winter rley nd winter rpe were grown on 47.7 % of the entire rle lnd in Germny. Considering dditionlly the cultivtion of silge corn, four different crop species were cultivted on 65 % of Germn fields (Sttistisches Bundesmt, 2013). However, the proportion of these crops in crop rottions is not uniformly distriuted cross Germny due to different soil nd climtic conditions. Therefore, in mny cropping systems only one spring seeded crop occurs within period of three or even four yers. Especilly in low diverse cropping systems with no periodiclly chnge etween spring nd fll seeded crops ecome pests, diseses nd especilly weeds more nd more n importnt prolem (Blckshw et l., 1994; Brust nd King, 1994; Guo et l., 2005). To minimize crop injury y pests, diseses nd weeds in those cropping systems, incresed ppliction of pesticides nd intensive tillge with the moldord plow re required (Kegode et l., 1999; Légère et l., 1997). However, tillge with the moldord plow is cost expensive, time consuming, dmges the soil structure, reduces the wter infiltrtion, increses the risk of soil erosion nd hrms the soil iology (Gehrdt 1

12 1 Generl Introduction et l., 1985). Therefore, frmers chnged their cultivtion mngement nd used less intensive tillge equipment like chisels plows nd disc hrrows or they even omitted soil tillge. Although reduced tillge nd conservtion griculture improve the stility of cropping systems ginst environmentl fctors, the comintion with monotonous crop diversity results in incresed occurrence of pests, diseses nd weeds (Anderson et l., 1998). Resons for the incresing weed popultion in those cropping systems re the sty of weed seeds in soil lyers from which they cn emergence nd furthermore the sence of lternting growth conditions which preserves the repeted propgtion of weed species with well dpted life cycle to the occurring gronomic prctice (Benvenuti et l., 2001; Liemn nd Dyck, 1993). To control the incresing weed popultion frequent ppliction of hericides during vegettion of the csh crop ut lso during fllow periods re necessry to prevent weeds from seed dispersl (Ghosheh nd Al-Hjj, 2005). Especilly the seed dispersl of weeds during fllow periods increses the weed seednk nd results in higher weed emergence in the following yers (Crdin et l., 2002; Muluget nd Stoltenerg, 1997). Even if fllow periods re too short for seed dispersion or if reduced weed growth occurs like in winter months, the ppliction of urn down hericide is common prctice prior seeding of the following csh crop, especilly in cropping systems with reduced tillge. Reson therefore is the fct tht most hericides re not le to control mture weeds without dmging growth or yield formtion of the crop. However, lso with frequently ppliction of hericides, weed density is still high in such griculturl systems. Furthermore, n incresed development of hericide resistnces cn e oserved due to the repeted ppliction of hericides with identicl mode of ction (Chuvel et l., 2009; Price et l., 2011). To void or t lest reduce these prolems of conservtion tillge nd low csh crop diversity, cultivtion of cover crops nd undersown crops cn cn e possile solution to increse the sustinility of those cropping systems. 2

13 1.2 Benefits of cover crops 1.2 Benefits of cover crops Cover crops re plnts which grow etween two csh crops nd provide multiple enefits to the groecosystem (Hrtwig nd Ammon, 2002). Among others, cover crops re le to prevent soil erosion y wind nd wter, reduce leching of wter solule nutrients, improve the soil structure nd uild verticl mcro pores which increse wter infiltrtion (De Bets et l., 2011; Hooker et l., 2008; Prlk nd Özsln Prlk, 2010; Stirzker nd White, 1995). Due to shding of the soil surfce in summer months, cover crops re le to reduce the temperture of the upper soil lyer, which is eneficil for the microil community (Levy et l., 2007). Cultivted in fll insted of fllow, cover crops re lso le to suppress growth of weeds nd volunteer crops y competition for light wter nd nutrients or through the relese of llelopthic sustnces (Bezuidenhout et l., 2012; Cremer et l., 1996). If summer nnul cover crops suppress weeds nd volunteer crops during their vegettion in fll nd freeze in frosty winter nights, they my provide seeded without living plnts in spring. Therefore, successful cultivtion of cover crops cn void tillge or the ppliction of urn down hericide like glyphoste in fll nd prior to csh crop seeding in spring. To chieve these eneficil effects, cover crop should offer the following growth chrcteristics: long period of possile seeding dtes in fll. fst germintion nd emergence even under dry nd unfvorle soil conditions. fst soil coverge within few weeks fter sowing. long time of vegettive growth to produce high mount of shoot nd lso root dry mtter. no development of fertile seeds to prevent growth of weedy cover crops in the next csh crop. enough frost tolernce to void erly frost kill efore the end of the vegettion period in fll. 3

14 1 Generl Introduction In the lst yers, only few summer nnul cover crop species were cultivted in Germny (Sttistisches Bundesmt, 2007). Minly yellow mustrd, oilseed rdish nd phceli were cultivted, ecuse there re esy to mnge nd well dpted to growth conditions in fll. Seeded efore mid of August, yellow mustrd, oilseed rdish nd phceli offer only short period of vegettive growth due to long-dy photoperiodism, which highly reduces their eneficil effects. However, compred to seeding dtes t end of August, cover crops provide in generl more enefits if there were plnted in summer immeditely fter hrvest of the previous csh crops. Due to n erly seeding dte, cover crops chieve longer time for vegettion during wrm nd sunny dys t the end of summer, which results in higher ove nd elow ground dry mtter production (Fourie et l., 2001). Therefore new cover crops species re required which get long with erly seeding dtes immeditely fter hrvest ut lso with cool nd riny growth conditions in fll. One of those potentil new cover crop species could e trtry uckwhet (Fgopyrum ttricum (L.) Gertn.) ecuse it hs fst youth growth nd the ility of rpid soil coverge due to its rod leves (Cmpell, 1997). Another potentil new cover crop species for Centrl Europe is forge rdish (Rphnus stivus L. vr. longipinntus), which is lredy cultivted s cover crop in in the Mid-Atlntic region of the USA (White nd Weil, 2010). Forge rdish is le to cover the soil surfce within few weeks fter sowing. Furthermore it hs the ility to penetrte even through compcted soil lyers with its vigorous tproot (Lwley et l., 2011). Lopsided ot (Aven strigos Schre.) nd red ot (Aven yzntin K. Koch) re lso potentil cover crop species for Centrl Europe. Lopsided ot is populr cover crop in no-till cropping systems in south Americ (Derpsch et l., 1986). It is chrcterized y rpid growth nd high iomss production, which re suitle chrcteristics for cover crop. Red ot is minly cultivted for forge nd grin production in south Brzil nd is lso used s cover crop in no-till systems (Mrtinez et l., 2010). The suitility of red ot s cover crop hs only een exmined in reduced extend. However, due to its close reltion to common ot (Aven stiv L.), which is lso suitle cover crop successful cultivtion s summer nnul cover crop could e possile. 4

15 1.3 Benefits of undersown crops A further potentil cover crop species is niger (Guizoti yssinic (L.f.) Css.), n nnul herceous plnt from the Astercee fmily. Niger hs rod leves, fst growth within the first few weeks fter sowing nd the ility to uild up huge mount of dry mtter. Its origin is Ethiopi, where it is cultivted s n oilseed crop (Ydv et l., 2012). Niger grows on wide rnge of soil types ut needs tempertures etween 15 C nd 23 C for good growth (Getinet nd Shrm, 1996). Sorghum (Sorghum icolor L. Moench) is summer nnul C 4 grss which offers est growth in wrm nd sunny environments (Snpp et l., 2005). It is le to close the soil surfce rpidly nd produces lrge mount of dry mtter (Ngoujio et l., 2003). Sorghum hs high ility for weed suppression y competition for min growth fctors nd lso due to the relese of llelochemicls from living nd decomposing plnt tissue (Bicksler nd Msiuns, 2009). The lst potentil new cover crop species is grin mrnth (Amrnthus cruentus L.) which ws only tested s cover crop in few studies until now. But due to its rod nd shllow ngled leves nd fst growth it could e well suited s cover crop (Boer et l., 2008; Mennn et l., 2009). If successful cultivtion of those new cover crop species in Centrl Europe is possile, frmers get more opportunity for cover crop cultivtion, which my result in more stle cropping system nd reduced ppliction of pesticides. 1.3 Benefits of undersown crops Undersown crops re plnts which re seeded either together with, or shortly fter csh crops, which re clled min crops if they re cultivted together with undersown crops. Undersown crops re grown s living ground cover during nd lso fter the growing seson of the min crop (Hrtwig nd Ammon, 2002). Like summer or fll seeded cover crops, undersown crops re le to reduce erosion, enhnce the soil microil ctivity, nd could increse the soil orgnic mtter, which improves the storge of plnt nutrients nd wter (Brndsæter et l., 2012; Brelnd, 1995; Känkänen nd Eriksson, 2007; Nkmoto nd Tsukmoto, 2006). Furthermore, undersown crops hve the ility to suppress or prevent the germintion nd growth of weeds during nd fter the vegettion of the min crop (Bllré nd Csl, 2000; Kruk et l., 2006). 5

16 1 Generl Introduction However, not ll plnts hve the ility to hndle the previous mentioned ims. For usge s undersown crop, plnt species should e esy to rodcst in lredy growing plnt stocks, germinte even under dry nd unfvorle seeded conditions nd should offer n dequte growth under limited light conditions. After estlishment, no negtive interference on yield formtion of the min crop should occur neither y competition out limited growth fctors nor due to relese of llelopthic sustnces (Bezuidenhout et l., 2012; Crof et l., 2007; den Hollnder et l., 2007; Liedgens et l., 2004; Putnm nd DeFrnk, 1983). Also smll shoot growth is eneficil to prevent competition out spce nd light or interruption t hrvest (Hively nd Cox, 2001). Furthermore, the undersown crop should not e host for pests nd diseses or ecome weed in the susequent crop due to seed propgtion or regrowth. Especilly forge nd grsslnd plnts chieve these requirements in most cses. Therefore, memers of the Pocee nd Fcee plnt fmily re minly used s undersown crops. In Germny mny undersown crop species re ville which re well dpted to locl conditions. Beside others, perennil ryegrss (Lolium perenne L.), Itlin ryegrss (Lolium multiflorum Lm.) nd red fescue (Festuc rur L.) re commonly used grss species (Kunelius et l., 1992). From the fce fmily, primrily white clover (Trifolium repens L.), red clover (Trifolium prtense L.) nd suterrnen clover (Trifolium suterrneum L.) re populr undersown crops (Deguchi et l., 2007; Echtenkmp nd Moomw, 1989; Ilnicki nd Enche, 1992). The min dvntge of legume undersown crops is their ility to fix tmospheric nitrogen, due to symiosis with Rhizoium cteri, which cn e trnsferred to the min crop or is ville in the susequent crop (Boller nd Nöserger, 1987; Burity et l., 1989; Jensen, 1996; Mllrino et l., 1990). Due to their shllow ngled leves, legumes hve fster soil coverge thn grsses, which is n importnt fctor for the suppression of weeds. While legumes hve tproot with reltively smll mount of fine roots, grss species offer firous root system, which llows n enhncement of the soil structure nd intensive depletion of wter nd nitrogen(brelnd, 1995; Crine et l., 2003). Undersown crops re minly cultivted in cerels nd corn, ecuse in those crops no growth nd yield decrese or interference during the 6

17 1.3 Benefits of undersown crops hrvest process occurs if dpted mngement strtegies re relized. To prevent the min crop from yield reduction, while dequte growth of undersown crops (e.g. for weed suppression) is still possile, it is importnt to hrmonize the undersown crop nd the min crop either y selecting suitle plnt species or y culturl prctice. By the vrition of culturl prctice frmers cn dpt certin undersown crop to n otherwise unsuitle min crop y djusting plnt density, irrigtion, fertiliztion nd the time of undersown crop estlishment. Especilly, the sowing dte hs huge influence on the growth nd competition ility of undersown crops. The possile period of undersown crop estlishment depends on the growth nd competition ility of the undersown crop species nd the min crop. Due to dpted comintion of undersown crop species, min crop nd sowing dte it cn e possile to cultivte even highly competitive undersown crop species in sensitive min crop stnds without yield decrese. On the other hnd it is lso possile to rech good growth of low competitive undersown crop species in fst growing min crops. With hrmonized mngement strtegy it cn e possile to chieve good growth of different undersown crop species under mny environmentl situtions, which is required for sustinle weed suppression. Due to weed suppression with undersown crops it could e possile to reduce the mount of pplied hericides especilly in cropping systems with n reduced mount of tillge. 7

18 1 Generl Introduction 1.4 Ojectives of this thesis The ojectives of this thesis were: to evlute the suitility of new cover crop species for cultivtion in Centrl Europe. to evlute the ility of common nd new cover crop species for suppression of weeds nd volunteer grin under Germn growing conditions fter hrvest of grin cerels in fll. to determine if cultivtion of cover crops in previous fll cn reduce the weed density in spring prior seeding next crop. to sses if mngement of undersown crops influences the growth nd yield formtion of the min crop. to sses if mngement of undersown crops influences their ility to suppress weeds. 8

19 2 Pulictions The pulictions relted to this work re listed s follows: Reviewed pulictions: Wrum Untersten und Zwischenfrüchte wieder Bedeutung zur Unkrutregulierung in Europäischen Ackerusystemen ekommen Growth nd weed suppression ility of common nd new cover crops in Germny Conference proceedings: Lopsided ot (Aven strigos) s new summer nnul cover crop for weed suppression in Centrl Europe Sumitted (in review): Evlution of Three Potentil Cover Crops for Weed Suppression in Centrl Europe Mngement of undersown crops influences their competitiveness with cerels nd weeds A riefly description of the pper content is given in the front of every section. Plese note tht only the strcts of the pulictions re included due to the coprights of the pulishers, except where sumitted versions were not yet pulished. 9

20 2 Pulictions 2.1 Wrum Untersten und Zwischenfrüchte wieder Bedeutung zur Unkrutregulierung in Europäischen Ackerusystemen ekommen Section 2.1 gives n overview out resons why cover crops nd undersown crops re importnt for weed suppression in Europen cropping systems. The section includes three field experiments which show the successful suppression of weeds y cover crops nd undersown crops. The cover crop section of the pper descries the suppression of weeds nd volunteer grin in fll y different cover crop species nd gives rief introduction out the underlying mechnisms. The undersown crop section of the pper descries the growth of different undersown crop species during vegettion nd fter hrvest of the min crop. Furthermore, the undersown crop section shows tht growth nd yield formtion of the min crop not necessrily were influenced y the different undersown crop species. 10

21 Wrum Untersten und Zwischenfrüchte wieder Bedeutung zur Unkrutregulierung in Europäischen Ackerusystemen ekommen / Why Undersown nd Cover Crops Become Importnt Agin for Weed Suppression in Europen Cropping Systems Jochen Brust, Rolnd Gerhrds, Theodor Krnis, Luci Ruff nd Alexndr Kipp Originlly pulished in: Gesunde Pflnzen (ISSN: ) Volume 63, Numer 4, Pges , 2011 DOI: /s Springer, Berlin/Heidelerg, Germny Institute of Phytomedicine, University of Hohenheim, Otto-Snder-Strße 5, Stuttgrt, Germny

22 2 Pulictions Zusmmenfssung Die positiven Wirkungen von Zwischenfrüchten und Untersten uf ds Agrrökosystem sind ereits vielfch elegt. In europäischen Ackerusystemen ht sich der Anteil n Winterungen strk erhöht, weshl Zwischenvegettionszeiten für den Anu von Zwischenfrüchten verkürzt sind. In dieser Studie wurde untersucht, o Zwischenfrüchte und Untersten uch Unkräuter in solchen Anusystemen effektiv unterdrücken können. Hierzu wurden in den Jhren 2008 is 2010 n der Universität Hohenheim drei Feldversuche durchgeführt. Weißklee (Trifolium repens) und Deutsches Weidelgrs (Lolium perenne) konnten ls Unterst in Weizen und Dinkel die Dichte und Trockenmsse der Unkräuter verringern ohne die Bestndesdichte oder den Kornertrg des Getreides negtiv zu eeinflusst. Nch der Getreideernte ildete sich innerhl von zwei Wochen us der Unterst ein dichter Pflnzenestnd. Im dritten Feldversuch wurden Gelsenf (Sinpis l), Phceli (Phceli tncetifoli), Sndhfer (Aven strigos) und eine Gemenge us Alexndrinerklee (Trifolium lexndrinum), Stwicke (Vici stiv), Ttrischer Buchweizen (Fgopyrum ttricum) und Rmtillkrut (Guizoti yssinic) unmittelr nch der Weizenernte etliert. Die Zwischenfrüchte liefen schnell uf und verringerten die Anzhl und Biomsse der uflufenden Unkräuter. Gelsenf verringerte die Sprossmsse der Unkräuter um 93 %. Sndhfer reduzierte die Wurzelmsse der Unkräuter um 97 % und die Unkrutdichte um 90 %. Vorussetzung hierfür ist jedoch ein rsches oersowie unterirdisches Wchstum der Zwischenfrüchte, verunden mit einer intensiven Beschttung der Unkräuter. Die Untersuchungen elegen dss Zwischenfrüchte und Untersten, uch in intensiven Ackerusystemen, einen Beitrg zur nchhltigen und umweltschonenden Bewirtschftung leisten können. Schlüsselwörter: Untersten, Zwischenfrüchte, Unkrutregulierung 12

23 2.1 Untersten und Zwischenfrüchte zur Unkrutregulierung Astrct Cover crops nd under-sown crops influence the groecosystem in mny positive wys nd hve the ility to suppress weeds. However, the proportion of winter nnul cerels in Europen cropping system hs strongly incresed, which consequently reduced the time for cover crop cultivtion. In this study, it ws investigted if cover crops nd undersown crops hve the ility to reduce weed infesttions lso in rottions with high percentge of winter nnul cerels. Therefore, three field experiments were conducted t the University of Hohenheim from 2008 until Trifolium repens nd Lolium perenne reduced weed density nd iomss in Triticum estivum nd Triticum spelt, when they were cultivted s under-sown crops. Both under-sown crops hd no negtive effect on yield of cerels. Until 14 dys fter hrvest, under-sown crops estlished dense plnt cnopy. In the third experiment, Sinpis l, Phceli tncetifoli, Aven strigos nd mixture of Trifolium lexndrinum, Vici stiv, Fgopyrum ttricum nd Guizoti yssinic were cultivted directly fter hrvest of winter whet. The cover crops emerged fter few dys nd were le to reduce the density nd iomss of weeds. Sinpis l reduced ove-ground weed iomss y 93 %. Aven strigos suppressed root growth of weeds y 97 % nd weed density y 90 %. To chieve high weed suppression, it is necessry for cover crops to emerge quickly nd grow rpidly until complete soil coverge. The results underline the cpility of under-sown nd cover-crops to promote sustinle nd environmentl friendly cropping system. Key words: Cover crops, Under-sown crops, Weed control, Weed suppression 13

24 2 Pulictions 2.2 Growth nd weed suppression ility of common nd new cover crops in Germny Section 2.2 dels with the growth nd weed suppression ility of common nd new cover crop species in Germny. This study evlutes the suitility of trtry uckwhet, forge rdish, red ot nd grin mrnth for cultivtion in Germny nd compre it to the common cover crops yellow mustrd, oilseed rdish nd phceli. Results presented in this section were collected in four field experiments t three loctions in south-west nd estern Germny during the yers 2010, 2011 nd Beside the growth chrcteristics of cover crops, which included emergence, soil coverge nd dry mtter ccumultion, the weed suppression ility of cover crop species in fll nd the weed density in spring were mesured s well. 14

25 Growth nd weed suppression ility of common nd new cover crops in Germny Jochen Brust, Wilhelm Clupein nd Rolnd Gerhrds Originlly pulished in: Crop Protection (ISSN: ) Volume 63, Pges 1 8, Septemer 2014 DOI: /j.cropro Elsevier Inc., Phildelphi, Pennsylvni, USA Institute of Phytomedicine, University of Hohenheim, Otto-Snder-Strße 5, Stuttgrt, Germny Institute for Crop Production nd Grsslnd Reserch, University of Hohenheim, Fruwirthstrße 23, Stuttgrt, Germny

26 2 Pulictions Astrct Cover crops re le to provide multiple enefits for the groecosystem nd frmers. Cover crops re le to suppress weeds during fll nd winter, which is min requirement for the reduction of tillge nd hericides. However, only few cover crop species re currently grown in Germny. Therefore, four new cover crop species (trtry uckwhet, forge rdish, red ot nd grin mrnth) were compred with common cover crop species (white mustrd, oilseed rdish nd phceli) regrding their soil coverge, dry mtter production nd weed suppression ility. White mustrd emerged fster thn ll other cover crops nd uild the most shoot dry mtter t oth loctions in southwest Germny twelve weeks fter plnting (WAP). Only oilseed rdish ws le to reduce the weed dry mtter t ll loctions eight WAP. Phceli reduced weed density y 77 % t Meiereihof twelve WAP. Trtry uckwhet provided the highest soil coverge four WAP, offered the most shoot dry mtter eight WAP nd ws le to reduced weed dry mtter y more thn 96 % t Meiereihof nd Ihinger Hof twelve WAP. Forge rdish showed est root growth nd reduced the weed density in spring y more thn 81 % t ll loction. Red ot nd grin mrnth emerged slower, produced reduced mount of iomss thn the other cover crops nd were not le to suppress weeds. The results suggest tht trtry uckwhet nd forge rdish re well suited for cultivtion s cover crops in Germny due to their fst growth nd good suppression of weeds. Keywords: Root growth, Weed suppression, Weed crop interctions, Volunteer crops 16

27 2.2 Lopsided ot s new cover crop in Centrl Europe 2.3 Lopsided ot (Aven strigos) s new summer nnul cover crop for weed suppression in Centrl Europe Section 2.3 descries the growth nd weed suppression ility of lopsided ot to evlute its suitility for cultivtion s new summer nnul cover crop in Centrl Europe. Therefore, emergence, shoot nd lso root growth of lopsided ot were mesured in pot nd field experiment nd compred to common cover crop species. Additionlly the ility of lopsided ot to suppress weeds in fll nd spring ws mesured in the field experiment. 17

28 Lopsided ot (Aven strigos) s new summer nnul cover crop for weed suppression in Centrl Europe / Ruhfer (Aven strigos) ls neue Zwischenfrucht zur Unkrutunterdrückung in Mitteleurop Jochen Brust nd Rolnd Gerhrds Originlly pulished in: Proceedings 25 th Germn Conference on Weed Biology nd Weed Control Mrch 13-15, 2012, Brunschweig, Germny Julius-Kühn-Archiv 434/1 (ISSN: ) Pges: DOI: /jk Institute of Phytomedicine, University of Hohenheim, Otto-Snder-Strße 5, Stuttgrt, Germny

29 2.3 Lopsided ot s new cover crop in Centrl Europe Astrct Lopsided ot (Aven strigos) is common summer nnul cover crop in Brzil since mny yers. Two experiments were crried out in Stuttgrt- Hohenheim in 2010 to compre the growth nd weed suppression ility of lopsided ot with yellow mustrd (Sinpis l), phceli (Phceli tncetifoli) nd cover crop mixture. The emergence nd dry mtter production of the cover crop species were nlyzed in pot experiment. Lopsided ot uild 20.7 dt h 1 of shoot- nd 5.5 dt h 1 of root dry mtter twelve weeks fter plnting. A field experiment ws estlished fter hrvest of winter whet in summer. The soil ws prepred with disc hrrow nd cover crops were sown the next dy. At four week intervls, dry mtter nd plnt density of cover crops, weeds nd volunteer whet were mesured. Twelve weeks fter plnting, 17.8 dt h 1 of shootnd 6.2 dt h 1 of root dry mtter ws uilt y lopsided ot. Lopsided ot ws le to reduce the shoot dry mtter of weeds nd volunteer whet y 98 %, which ws the est result of ll cover crops. Cover crops were le to reduce the root dry mtter of weeds nd volunteer whet y 55 % to 97 %. While density of 54.5 plnts m 2 ws mesured in the weedy control plots, only 5.5 plnts m 2 were counted in plots of lopsided ot. The results suggest tht lopsided ot could e well suited for the suppression of weeds nd volunteer whet in utumn. Furthermore, its cultivtion would lso increse the numer of cover crops in Centrl Europe. Keywords: Competition, Field experiment, Pot experiment, Root, Shoot, Volunteer whet 19

30 2 Pulictions Zusmmenfssung Ruhfer (Aven strigos) wird vor llem in Brsilien ls Zwischenfrucht ngeut. Um die Eignung von Ruhfer zur Unterdrückung von Unkräutern/Ausfllgetreide mit Gelsenf (Sinpis l), Phceli (Phceli tncetifoli) sowie einer Zwischenfruchtmischung zu vergleichen wurden im Jhre 2010 zwei Versuche in Stuttgrt Hohenheim durchgeführt. Auflufen sowie Wchstum der Zwischenfrüchte wurden in einem Topfversuch estimmt, ei welchem Ruhfer eine Spross- sowie Wurzel- Trockenmsse von 20,7 dt h 1 und 5,5 dt h 1 zwölf Wochen nch Ausst ildete. Ein Feldversuch wurde nch Winterweizen etliert um Anzhl und Trockenmsse der Zwischenfrüchte, der Unkräuter und des Ausfllgetreides zu messen. Die Ausst erfolgte unmittelr nch der Weizenernte im Anschluss n eine c. 5 cm tiefe Bodenereitung mit einer Kurzscheienegge. Ruhfer konnte nch zwölf Wochen eine Sprossund Wurzel-Trockenmsse von 17,8 dt h 1 und 6,2 dt h 1 ilden. Ds Spross-Wchstum der Unkräuter und des Ausfllgetreides konnte von Ruhfer um 98 % reduziert werden, der höchste gemessene Wert. Die Zwischenfrüchten konnten die Wurzel-Trockenmsse der Unkräuter und des Ausfllgetreides zwischen 55 % und 97 % reduziert. Während in den Kontrollprzellen 54,5 Unkräuter m 2 wuchsen wurden in den Ruhfer- Przellen nur 5,5 Unkräuter m 2 gemessen. Die Ergenisse der Versuche legen nhe dss Ruhfer sehr gut Unkräuter sowie Ausfllgetreide unterdrücken knn. Der Anu von Ruhfer würde zu einer Bereicherung des isherigen Spektrums n Zwischenfrüchten in Mitteleurop führen. Stichwörter: Ausfllgetreide, Feldversuch, Konkurrenz, Spross, Topfversuch, Wurzel 20

31 2.3 Evlution of Potentil Cover Crops for Weed Suppression 2.4 Evlution of Three Potentil Cover Crops for Weed Suppression in Centrl Europe Section 2.4 includes the evlution of the three potentil cover crop species, nmely niger, sorghum nd lopsided ot, for cultivtion nd weed suppression in Centrl Europe. The section includes results from five fieldnd two pot experiments which were conducted in south-west nd estern Germny from 2010 to Different growth chrcteristics, which re importnt for the successful cultivtion of cover crops like soil coverge, ove nd elowground dry mtter ccumultion were mesured during the study. Furthermore, the ility of the three potentil cover crops to suppress common weed community in fll nd prticulr the control of mono nd dicotyledonous weeds were evluted. 21

32 Evlution of Three Potentil Cover Crops for Weed Suppression in Centrl Europe Jochen Brust, Wilhelm Clupein nd Rolnd Gerhrds Sumitted to: Weed Technology ISSN: Allen Press Inc., Lwrence, Knss, USA Institute of Phytomedicine, University of Hohenheim, Otto-Snder-Strße 5, Stuttgrt, Germny Institute for Crop Production nd Grsslnd Reserch, University of Hohenheim, Fruwirthstrße 23, Stuttgrt, Germny

33 2.4 Evlution of Potentil Cover Crops for Weed Suppression Summry Cover crop cultivtion offers lots of dvntges to groecosystems. However, currently only few cover crop species re cultivted in Centrl Europe. To enlrge this numer, two experiments were conducted in 2010 nd 2011 t four loctions in southwestern nd estern Germny, to evlute the growth nd weed suppression ility of niger, lopsided ot nd sorghum. In the cover crop evlution experiment, niger nd sorghum show comprle soil coverge nd dry mtter production s white mustrd, common cover crop in Centrl Europe. Lopsided ot offered vrile results regrding its soil coverge nd dry mtter ccumultion. Niger hd high competitive ility nd ws le to reduce shoot dry mtter of weeds t ll loctions. Sorghum could reduce the shoot dry mtter of weeds y 69 % t Meiereihof nd 88 % t Ihinger Hof. Until spring, lopsided ot ws le to reduce weed density y 97 % t Ihinger Hof nd 99 % t Trossin. In the competition experiment, niger nd sorghum were le to suppress growth of oth weed species t Ihinger Hof, however, t Hohenheim, they were not le to suppress root growth of nnul ryegrss. Lopsided ot hd prolems to reduce growth of nnul ryegrss t oth loctions. The results suggest tht ll plnt species my hve the potentil for suitle cultivtion s cover crops in Centrl Europe. Nomenclture: niger, Guizoti yssinic (L.f.) Css.; lopsided ot, Aven strigos Schre.; sorghum, Sorghum icolor L. Moench; forge rpe, Brssic npus L.; nnul ryegrss, Lolium multiflorum Lm. Key words: Niger, Sorghum, Lopseded ot, Weed dry mtter, Weed density, Root growth 23

34 2 Pulictions Introduction Cover crops re n importnt prt of griculturl systems to sve nd improve soil nd crop qulity. Cover crops re le to reduce soil erosion y wind nd wter (De Bets et l., 2011), enhnce wter infiltrtion (Gulick et l., 1994), increse soil orgnic cron (Kuo et l., 1997), prevent the leching of nitrte into groundwter (Logsdon et l., 2002), reduce soil compction nd uild mcro pores for the susequent csh crop (Willims nd Weil, 2004). Another importnt property of cover crops is the suppression of weeds nd volunteer crops fter hrvest. Cover crops re le to suppress weeds y competition for min growth fctors (light, wter nd nutrients) or the relese of llelochemicls from living nd decomposing plnt tissue (Bezuidenhout et l., 2012; Cremer et l., 1996; Dhim et l., 2006). Tody, only smll numer of cover crop species re grown in Centrl Europe. Especilly white mustrd (Sinpis l L.) is cultivted, ecuse it is esy to mnge nd well dpted to fll growth conditions. However, white mustrd requires reltively high mounts of soil wter, moderte tempertures nd short dy-length for high dry mtter production nd good weed suppression. Therefore, other cover crops re required, which rpidly cover the soil nd produce high mount of dry mtter for good weed control, even under dry nd unfvorle conditions directly fter summer hrvest. In Centrl Europe, successful cultivtion of sutropicl plnt species s summer nnul cover crops seems to e possile, ecuse they only grow short period of time during reltively wrm months t the end of summer. In most yers, this is enough time for good vegettive growth, ut not for flowering nd mturing of seeds. Another chrcteristic of sutropicl plnts, which could e enefit for frmers, is their poor frost resistnce. This ensures tht cover crops re killed y frost over winter nd do not grow s weed in the following csh crop. One of these potentil new cover crops is niger (Guizoti yssinic (L.f.) Css.), n nnul herceous plnt which elongs to the Astercee fmily. Tody, niger is cultivted s n oilseed crop in mny prts of Est Afric, Indi nd Pkistn (Ydv et l., 2012). Depending on plnt density, the shoot is modertely- to well- rnched nd could rech height etween 24

35 2.4 Evlution of Potentil Cover Crops for Weed Suppression 0.5 nd 1.5 m. Its leves re cm long, 3-5 cm wide, nd with shllow lef ngle oppositely rrnged t the shoot. Niger grows on wide rnge of soil types, even t low ph-vlue. However, for good growth, tempertures etween 15 C nd 23 C nd moderte mount of rinfll re required (Getinet nd Shrm, 1996). Lopsided ot (Aven strigos Schre.) is n importnt cover crop for conservtion-tilled soyens in southern Brzil nd Prguy. For few yers now, lopsided ot hs lso een grown in conservtion griculture systems in the southestern USA nd southwestern Austrli (Buer nd Reeves, 1999; Flower et l., 2012). Lopsided ot seems to e well suited s cover crop, due to rpid growth nd high iomss production. It is le to suppress weeds y direct competition nd llelopthy (Price et l., 2008). Sorghum (Sorghum icolor L. Moench) is summer nnul C 4 grss which is well dpted to dry, wrm nd sunny environments (Snpp et l., 2005). Commonly, it is cultivted for grin production or s forge crop. Used s cover crop, sorghum rpidly closes cnopy, produces lrge mount of dry mtter, immoilizes lechle nutrients nd is le to reduce soil compction (Ngoujio et l., 2003). Sorghum is strong competitor nd le to suppress even perennil weeds like Cnd thistle (Cirsium rvense (L.) Scop.) due to physicl interference nd the relese of llelochemicls (Bicksler nd Msiuns, 2009). The ojectives of this study were to determine the growth chrcteristics nd the weed suppression ility of niger, lopsided ot nd sorghum to evlute their suitility for cultivtion s cover crops in Centrl Europe Mterils nd Methods Experimentl sites. A cover crop evlution- nd competition experiment were conducted t four loctions in southwestern nd estern Germny. The cover crop evlution ws crried out in 2010 in pots t the University of Hohenheim (48 70 N, 9 20 E, 407 m ltitude) to study growth of cover crops in fll. In 2011, the cover crop evlution ws conducted under field conditions t 25

36 2 Pulictions the experimentl sttion Meiereihof (48 71 N, 9 21 E, 435 m ltitude), Ihinger Hof (48 74 N, 8 92 E, 478 m ltitude) nd Trossin (51 61 N, E, 120 m ltitude) to mesure dditionlly the weed suppression in fll nd spring. The competition experiment ws done in 2011, in pots t the University of Hohenheim nd under field conditions t Ihinger Hof to study the interction of cover crops with dicotyledonous nd monocotyledonous model weed. Soil used in pots t Hohenheim in 2010 ws from Ihinger Hof, while in 2011, it ws from the experimentl sttion Heidfeldhof (48 71 N, 9 20 E, 430 m ltitude). Climte nd soil chrcteristics of the experimentl sites re presented in Tle 1. Tle 1: Averge climtic conditions, soil properties nd mount of soil minerl nitrogen (N min) in oth experiments. Cover crop evlution Competition experiment Ihinger Hof Trossin Hohenheim Meiereihof Hohenheim Ihinger Hof Av. Temp. ( C) Av. Percep. (mm) Soil texture Cly Lom Sndy Cly Lom Soil type - Hplic Luvisol Cly Lom Hplic Luvisol Sndy Lom Sndy Cly Lom Cly Lom Cmisol - Hplic Luvisol N min (kg h 1 ) Experimentl Design nd Tretments. The experimentl design in oth experiments ws rndomized complete lock with four replictions. Plots t ll loctions hd size of 2 m y 10 m. The cover crop evlution t Meiereihof nd Ihinger Hof ws conducted susequent to winter whet (Triticum estivum L.), while t Trossin cover crops were cultivted fter winter rley (Hordeum vulgre L.). Immeditely fter hrvest of the previous crop, strw ws removed nd the soil ws tilled with disc t depth of 5 cm. The field used in the competition experiment t Ihinger Hof ws cultivted s grsslnd until 2010, nd plowed in Jnury Before sowing, the seeded ws prepred with drill hrrow. Cover crops were seeded using 26

37 2.4 Evlution of Potentil Cover Crops for Weed Suppression plot seeder with doule disk openers nd row spcing of 11 cm to depth of 2 cm. At Hohenheim, pots were cultivted outdoors, to chieve comprle plnt growth s under field conditions. Pots hd size of 20 cm y 20 cm, height of 25 cm nd were filled with crushed nd sieved soil to llow dequte root growth. Cover crops were sown into pots y hnd t depth of 2 cm to ensure uniform plnt rrngement. Every pot ws irrigted using dripper irrigtion system to provide dequte wter supply without encrusting the soil surfce. No further fertilizer ws pplied neither in pots nor plots t ny loction, to see how cover crops respond to nutrient deficient soils. Used plnt species in the cover crop evlution t ll loctions were white mustrd, niger, lopsided ot nd sorghum with seeding rte of 12.7 kg h 1, 11.1 kg h 1, kg h 1 nd 44.9 kg h 1, respectively. White mustrd ws included s n dditionl tretment to compre the potentil new cover crops with common cover crop. To estimte the influence of cover crops on weed growth, weedy control tretment dditionlly occurred in the cover crop evlution experiment t Meiereihof, Ihinger Hof nd Trossin. Cover crops were seeded on August 12 th 2010, August 10 th 2011, August 4 th 2011 nd July 16 th 2011 t Hohenheim, Meiereihof, Ihinger Hof nd Trossin, respectively. In the competition experiment, niger, lopsided ot nd sorghum were seeded with the sme seeding rte s in the cover crop evlution. Used model weeds were nnul ryegrss (Lolium multiflorum Lm.) nd forge rpe (Brssic npus L.), which were seeded together with cover crops nd in single stnd with seeding rte of 21.6 kg h 1 nd 2.9 kg h 1, respectively. Cover crops nd oth weeds were seeded on July 7 th 2011 t Hohenheim nd on July 6 th 2011 t Ihinger Hof. To determine only the interference etween cover crops nd oth weeds, other plnts were removed y hnd. Dt Collection. Soil coverge ws mesured in the cover crop evlution t Hohenheim four nd eight weeks fter plnting (WAP), t Meiereihof nd Ihinger Hof four, six nd eight WAP, nd t Trossin eight WAP. To determine soil coverge, pictures were tken with digitl cmer from n re of 12 m 2 in the field nd from single pots t Hohenheim. Afterwrds, imges were nlyzed using ImgeJ Version Imges were converted into 27

38 2 Pulictions HSB-formt nd the green color of plnts ws seprted from re soil using the procedure Color Threshold. If required, leves of weeds were digitlly msked y hnd to seprte them from cover crops. Finlly, the msked green res were estimted with the Anlyze Prticles procedure. Dry mtter smplings were tken in the cover crop evlution experiment four, eight nd twelve WAP t Hohenheim, Meiereihof nd Ihinger Hof nd eight WAP t Trossin. Shoot nd root dry mtter smplings were collected from n re of 0.04 m 2, 0.25 m 2, 0.5 m 2 nd 0.25 m 2, t Hohenheim, Meiereihof, Ihinger Hof nd Trossin, respectively. In the competition experiment, plnt smples were hrvested twelve WAP from smplings size of 0.04 m 2 t Hohenheim nd 0.5 m 2 t Ihinger Hof. To mesure the shoot nd root dry mtter of cover crops nd weeds in pots nd plots, the complete soil monolith ws removed from the pot or plnts were excvted until depth of 30 cm. Roots of cover crops nd weeds were clened from soil with wter nd then crefully seprted y hnd. Afterwrds, roots were cut from shoots nd dried for three dys t 80 C. To determine the weed density, the numer of weeds ws counted with 0.1 m 2 frme t four rndomly selected plces in the plots t Meiereihof, Ihinger Hof nd Trossin, eight WAP nd t mid-mrch Sttisticl Anlysis. For sttisticl nlysis, the sttisticl lnguge R version 2.15 ws used (R Core Tem, 2012). Anlysis of vrince ws used to compre the sttisticl significnce of soil coverge, dry mtter of cover crops nd weeds, s well s weed density. To verify the requirements for sttisticl nlysis, the Shpiro-Wilk-test for normlity nd the Levene-test for homogeneity of vrince were used. If required, dt were trnsformed using squre-root or log trnsformtions to chieve the sttisticl ssumptions. Afterwrds, multiple comprison tests were conducted with the Tukey test t significnce level of α

39 2.4 Evlution of Potentil Cover Crops for Weed Suppression Results nd Discussion Wether Conditions. In 2010, climtic conditions were chrcterized y cool nd cloudy wether during Septemer nd Octoer which ws unfvorle for cover crop growth (Tle2). The second growing seson strted with cool tempertures nd high mounts of precipittion in July. However, from the eginning of August, good conditions for cover crop growth occurred. Especilly Septemer nd Octoer were dominted y wrm nd sunny wether in comintion with dequte supply of rinfll t ll loctions. During Novemer 2011, wether ws wrm t Meiereihof nd Ihinger Hof, while lmost no rinfll occurred t ll loctions. Tle 2: Air temperture nd precipittion during the growing sesons nd the 20-yer monthly verge t Hohenheim (Institute of Phytomedicine nd Meiereihof), Ihinger Hof nd Trossin. Loction Air temperture ( C) Precipittion (mm) Jul. Aug. Sept. Oct. Nov. Jul. Aug. Sept. Oct. Nov. Hohenheim Hohenheim Hohenheim ltm.-verge Ihinger Hof Ihinger Hof ltm.-verge Trossin Trossin ltm.-verge Cover crop evlution. Soil Coverge. No difference etween the soil coverge of white mustrd, niger nd sorghum could e mesured t ll loctions eight WAP (Figure 1). Niger ws le to cover the soil eight WAP y 88 % t Hohenheim nd 93 % t Meiereihof. Lopsided ot showed eight WAP lower soil coverge thn white mustrd nd niger t ll loctions expect Trossin. In contrst to the other cover crops, soil coverge of lopsided ot eight 29

40 2 Pulictions WAP vried in wide rnge etween 38 % t Hohenheim nd 85 % t Meiereihof. Sorghum covered the soil in lower mount thn white mustrd t Meiereihof four WAP, however, t Hohenheim nd Ihinger Hof, no difference could e mesured. The soil coverge of plnt is minly influenced y the the growth rte nd the lef morphology, in prticulr y the ngle nd re of leves. White mustrd nd niger re plnt species with rod nd shllow ngled leves, which llow them to completely cover the soil surfce within period of six WAP (De Bets et l., 2011). On the contrry, plnt species like lopsided ot show reduced soil coverge, especilly the first few WAP, due to their smll nd steeper ngled leves. As result of this lef morphology, it is necessry for such plnt species to produce high numer of leves or tillers for complete soil coverge in lter growth stges. Similrly to lopsided ot, sorghum hs steeper lef ngle tht cuses delyed soil coverge. However, due to its roder leves nd higher lef re, sorghum is le to cover the soil like rodlef cover crops. Soil coverge (%) Hohenheim 4 WAP 8 WAP Meiereihof c 4 WAP 6 WAP 8 WAP White mustrd Niger Lopsided ot Sorghum 0 White mustrd Niger Lopsided ot Sorghum Soil coverge (%) Ihinger Hof 4 WAP 6 WAP 8 WAP Trossin 8 WAP 0 White mustrd Niger Lopsided ot Sorghum 0 White mustrd Niger Lopsided ot Sorghum Figure 1: Soil coverge of cover crops. Brs represent men vlues ± stndrd devition. Within ech loction, nd mesurement dtes, significnt differences (α 0.05) re indicted y rs topped with different letters. 30

41 2.4 Evlution of Potentil Cover Crops for Weed Suppression Cover Crop Dry Mtter. At Meiereihof, dry mtter of white mustrd, niger nd sorghum ws more thn two times greter thn t the other loctions which ws minly result of higher N min content (Figure 2). Niger showed similr shoot nd root dry mtter s white mustrd t ll loctions eight WAP. At this mesurement dte, lopsided ot produced the lowest shoot dry mtter t Meiereihof nd Ihinger Hof. However, t Trossin, lopsided ot offered the est shoot growth. This vrile growth ws lso oserved in the southern USA, where lopsided ot offered dry mtter vlues etween 132 g m 2 nd 625 g m 2 (Price et l., 2006; Reeves et l., 2005). Lopsided ot hd etter root growth thn white mustrd nd niger t Hohenheim nd Ihinger Hof four WAP. This fst initil root growth from memers of the Pocee fmily compred to other plnt species ws lredy known from previous studies (White nd Weil, 2010). Sorghum offered similr shoot growth s white mustrd t Hohenheim, Meiereihof nd Trossin eight WAP while t Ihinger Hof lower dry mtter ws mesured. Sorghum produced higher root dry mtter thn white mustrd t Hohenheim nd Ihinger Hof eight WAP. Shoot dry mtter of sorghum, which rnged etween 101 g m 2 t Hohenheim nd 405 g m 2 t Meiereihof twelve WAP, ws smller thn reported y other scientists, which oserved vlues etween 520 g m 2 nd 870 g m 2 (Butler et l., 2012; Cremer nd Bldwin, 2000; Ngoujio nd Mennn, 2005). This ws minly result of Centrl Europen growth conditions with shorter nd cooler dys in fll, which my hve prevented higher dry mtter production of the C 4 -species sorghum. Niger ws the plnt species with the lowest frost tolernce of ll cover crops nd died due to slight frost t the end of Octoer t Meiereihof, Ihinger Hof nd Trossin, while sorghum grew until Decemer t Meiereihof. Lopsided ot ws le to survive short frost nights in fll, nd provide growth nd soil coverge up until long nd hevy frost periods in winter. The higher frost tolernce of lopsided ot is eneficil for cover crop cultivtion ecuse frosty nights with tempertures slightly elow 0 C occur reltively often in Centrl Europe lredy from mid-septemer, while dequte growing conditions for cover crops re possile until mid-octoer. 31