ISSN 1392-3196 ŽEMDIRBYSTĖ=AGRICULTURE Vol. 98, No. 3 (2011) 251 ISSN 1392-3196 Žemdirbystė=Agriculture, vol. 98, No. 3 (2011), p. 251–258 UDK 631.582:631.811.1/.3:633.11“321”]:631.559 Biomass production and nutrient binding of catch crops Liina TALGRE, Enn LAURINGSON, Arvo MAKKE, Ruth LAUK Estonian University of Life Sciences Institute of Agricultural and Environmental Sciences Kreutzwaldi 1, Tartu, Estonia E-mail: [email protected]Abstract The trials were carried out during the 2008–2010 growing seasons at the Estonian University of Life Sciences’ Department of Field Crop Husbandry. The experiments were performed to measure the amount of biomass produced by catch crops and how effectively they bind the soil nutrients. The ex- periment was performed four times on a Stagnic Luvisol (LVst). The catch crops were white mustard, fodder radish, faba bean, winter oil rape, winter oil turnip, Italian ryegrass, pea, rye and phacelia. The amount of biomass that catch crops produced differed significantly from year to year. Sowing time had a great effect on biomass production, with August having the greatest sum of effective temperatures. The best nutrient binders were pea and beans. In better growth years these crops bound 50–100 kg ha -1 N, 7–10 kg ha -1 P, 40–60 kg ha -1 K. Of Brassicaceae, white mustard and fodder radish produced the highest biomass, used up to 9 kg ha -1 P and up to 82 kg ha -1 K (2010, fodder radish) in the biological cycle of organic matter. The catch crops did not reduce soil NO 3 -N and NH 4 -N content compared to the control fields without catch crops variant. Key words: catch crops, biomass, nitrogen, potassium, phosphorus, C:N ratio, spring wheat yield. Introduction In recent years, many research groups from various countries have taken an interest in finding new ways of reducing the loss of plant-accessible soil nut- rients during vegetation-free periods. It is known that the mineralization of organic matter takes place in pe- riods before or after growing seasons (Powlson, 1993; Vos, Van der Putten, 2001); autumn ploughing also in- creases the risk of reducing nitrogen amounts because of leaching (Davies et al., 1996). One way to reduce nitrogen leaching is to use a crop rotation system which leaves some of the fields covered with plants for the winter. Along with grow- ing winter cereals or perennial grasses, one could also grow intermediate crops, i.e. catch crops. The research interest in growing catch crops and green manures is not new, but the use of such crops has decreased (Renius, Entrup, 2002). A catch crop may absorb residual N up to 200 kg ha -1 N and thus reduce N available for leaching and denitrifica- tion. The N uptake by the catch crop may depend on plant species, sowing date (determined by the harvest time of the previous crop), amount of available soil N and weather conditions (Van Dam, 2006). In addition to reducing nutrient leaching, catch crops improve soil quality by adding organic matter (Lord, Mitchell, 1998), avoiding topsoil ero- sion (Thorup-Kristensen et al., 2003), reducing the loss of organic matter, inhibiting pest/disease infesta- tion and reducing weeds. Plants from the Brassicaceae family are able to produce glycosinolates (both in their roots as well as their above-ground parts), which in- hibit root rot (Ilumäe et al., 2007). Therefore growing catch crops in a crop rotation system with cereals is of great importance, because it reduces the environmental stress on the soil and disrupts the disease development cycles. However, when choosing catch crops, it is im- portant to avoid growing biologically similar species together too often, to prevent transferring common pests and diseases. Recently, it has also been specu- lated that catch crops may influence the degradation potential of the soil for pesticides (Thorup-Kristensen et al., 2003). The most common catch crops are Brassicace- ae: fodder radish, white mustard, oilseed rape and tur- nip, but also cereals (rye), Italian ryegrass and phacelia. These catch crops are able to bind free nitrogen in the soil. Leguminous plants, which have the added advan- tage of binding nitrogen from the air, are also grown as catch crops. The efficiency of binding air nitrogen depends on the length of the growing season, crop rota- tion system and manuring (Peoples et al., 2001).
AbstractThetrialswerecarriedoutduringthe2008–2010growingseasonsattheEstonianUniversityofLifeSciences’ Department of Field Crop Husbandry. The experiments were performed to measure theamountofbiomassproducedbycatchcropsandhoweffectivelytheybindthesoilnutrients.Theex-perimentwasperformedfourtimesonaStagnic Luvisol(LVst).Thecatchcropswerewhitemustard,fodderradish,fababean,winteroilrape,winteroilturnip,Italianryegrass,pea,ryeandphacelia.Theamountofbiomassthatcatchcropsproduceddifferedsignificantlyfromyeartoyear.Sowingtimehadagreateffectonbiomassproduction,withAugusthavingthegreatestsumofeffectivetemperatures.Thebestnutrientbinderswerepeaandbeans.Inbettergrowthyearsthesecropsbound50–100kgha-1N,7–10 kgha-1P,40–60kgha-1K.OfBrassicaceae,whitemustardandfodderradishproducedthehighestbiomass,usedupto9kgha-1Pandupto82kgha-1K(2010,fodderradish)inthebiologicalcycleoforganicmatter.ThecatchcropsdidnotreducesoilNO3-NandNH4-Ncontentcomparedtothecontrolfieldswithoutcatchcropsvariant.
Theresearchinterestingrowingcatchcropsand green manures is not new, but the use of suchcropshasdecreased (Renius,Entrup,2002).AcatchcropmayabsorbresidualNupto200kgha-1Nandthus reduceNavailable for leachinganddenitrifica-tion.TheNuptakebythecatchcropmaydependonplantspecies,sowingdate(determinedbytheharvesttimeofthepreviouscrop),amountofavailablesoilNandweatherconditions(VanDam,2006).
In addition to reducing nutrient leaching,catch crops improve soil quality by adding organicmatter (Lord,Mitchell, 1998), avoiding topsoil ero-
sion (Thorup-Kristensen et al., 2003), reducing thelossoforganicmatter,inhibitingpest/diseaseinfesta-tionandreducingweeds.PlantsfromtheBrassicaceae familyareabletoproduceglycosinolates(bothintheirrootsaswellas theirabove-groundparts),whichin-hibitrootrot(Ilumäeetal.,2007).Thereforegrowingcatchcropsinacroprotationsystemwithcerealsisofgreatimportance,becauseitreducestheenvironmentalstressonthesoilanddisruptsthediseasedevelopmentcycles.However,whenchoosingcatchcrops,itisim-portanttoavoidgrowingbiologicallysimilarspeciestogether too often, to prevent transferring commonpestsanddiseases.Recently, ithasalsobeenspecu-lated that catchcropsmay influence thedegradationpotentialofthesoilforpesticides(Thorup-Kristensenetal.,2003).
ThemostcommoncatchcropsareBrassicace-ae:fodderradish,whitemustard,oilseedrapeandtur-nip,butalsocereals(rye),Italianryegrassandphacelia.Thesecatchcropsareabletobindfreenitrogeninthesoil.Leguminousplants,whichhavetheaddedadvan-tageofbindingnitrogen from the air, are alsogrownas catchcrops.Theefficiencyofbindingairnitrogendependsonthelengthofthegrowingseason,croprota-tionsystemandmanuring(Peoplesetal.,2001).
252 Biomass production and nutrient binding of catch crops
The catch crops are ploughed into the soilshortlybeforethegroundfreezes.Afterincorporationof the crop into the soil,Nmineralization starts, sothat,withgoodtiming,partofthemineralizedNmaybecomeavailableforthenextmainseasoncropallow-ingreductionoftheNapplicationforthatcrop(Vos,Van der Putten, 2001). Some researchers (Stenberget al.,1999)havefoundthatlateautumnploughingorspringploughingreducestheriskofNleaching.
Experiments were performed in the trialfieldstostudytheamountofbiomassformedbycatchcrops,howtheybindnutrientsandtheireffectontheplantavailableNinthesoil.ThepurposewastofindthemostoptimalcatchcropspeciesforEstoniancon-ditions.
Materials and methodsThetrialswerecarriedoutduringthe2008–
2010growingseasonsintheDepartmentofFieldCropHusbandryattheEstonianUniversityofLifeSciences(EMU), Institute ofAgricultural and EnvironmentalSciences(58°23′N,26°44′E).ThetrialwasrepeatedfourtimesonaStagnic Luvisol(LVst)(byWRBclas-sification), thehumuslayerofwhichhasthefollow-ingcharacteristics:Corg1.1–1.2%,Ntot0.10–0.12%,P110–120mgkg-1,K253–260mgkg-1,pHKCl5.9,soilbulkdensity1.45–1.50Mgm-3,thedepthofploughinglayerwas27–29cm.SoilanalyseswerecarriedoutatthelaboratoriesoftheDepartmentofSoilScienceandAgrochemistry,EMU.
Barleycv. ‘Inari’wasusedas theprecedingcrop. The field was prepared and catch crops weresownwithaKongskildesowingmachine(rowwidth12.5cm)immediatelyafterthebarleyharvesting:on25Augustin2008,14Augustin2009and2Augustin2010.
massofcatchcropsandtherootmassweremeasuredbeforeploughing.Samplesofabove-groundbiomassweretakenfrom1m-2andtherootmassfrom0–30 cmdepth (4 replications). The samples were dried andweighed.Accordingtothelengthofthegrowingpe-riod, the catch cropswere ploughed into the soil inthe2nd–3rdten-dayperiodofOctober.Ploughingdepthwas22–24cm.Beforeploughing,thecatchcropswereneithergroundnorcrushed.
Theeffectof catchcropswasmonitoredbygrowingspringwheatcv.‘Mooni’(2009,2010).Plantanalyses were conducted at the Department of SoilScience andAgrochemistryofEMU.Aciddigestionbysulphuricacidsolution(Methodsofsoil…,1986)was used to determineP andK content in the plantmaterial.Totalnitrogen,carbonandsulfurcontentofoven-dried samples (separately in undeground andabovegroundbiomass)weredeterminedbydrycom-bustion method on a “vario MAX CNS” elementalanalyzer(“Elementar”,Germany).
Researchdatawasprocessedbyusinganaly-sis of variance and correlation analysis. The differ-encesbetweentreatmentsareshownasstandarderror.To describe the growth period, the sum of effectivetemperatures (above 5°C) and precipitation average(mm)wasused(Table1).
Table 1. The sum of effective temperatures andprecipitationduringcatchcrops’growthperiod
YearSumofeffectivetemperatures,degree-days
Precipi-tationmm
Growthperiod/days
2008 352 134 72
2009 427 207 60
2010 602 225 72
Results and discussionSince cereals are prevalent in modern crop
Fromyear toyear, thereweregreatfluctua-tionsinthequantityofcatchcropbiomassproducedand depended on the sum of effective temperaturesduringthegrowingseason(R=0.63).Especiallysig-nificant positive correlations were detected betweenbiomass of fodder radish and sum of effective tem-peratures(R=0.88).In2008,becauseoftheweatherconditions, thecropwasharvestedat theendofAu-gust.As the sum of effective temperatureswas low
inAugustandSeptember(about30ºClowerthantheaverage from1948–2007), the catch cropsproducedamodest amount of biomass.The rather long dura-tionofthegrowingperiod(untiltheendofOctober)didnotcompensateforthelowtemperatures.Theto-talbiomassofcatchcropsvariedfrom570kgha-1forwinteroil rape to1720kgha-1 for fababean,whichbound13–52kgha-1N(Fig.1).Infodderradish,39%ofthetotalbiomassconsistedofroots;forothercropstherootshadasmallershareintheresultingbiomass.Previous research (Thorup-Kristensen, 2001) hasshownthatfodderradishformsastrongtaprootwithawell-spreadsystemofsideroots,whichenablesitto
ThedecompositionoforganicmatterdependslargelyontheC:Nratioandtheiroverallamount.ThesmallertheC:Nratiooforganicmatterandthegreateritsnitrogencontent,themorenitrogenismineralisedintosoilfromgreenmanure(Kumar,Goh,2002).TheC:Nratiooftheappliedorganicmattervariedfrom13(bean)to18(whitemustardandwinteroilseedrape).When organic matter is decomposed by microorga-nismsintheconditionslikethese,nosoilnitrogenisusedinthedecompositionprocessandnitrogenisim-mediatelyavailableforthemain(following)crop.
Note.Verticalbarsdenotestandarddeviation.
Figure 1.Biomassofcatchcrops,NandC:Nratioin2008
The ability of catch crops to bind P andKnutrientsforthemaincrophasbeenlessstudied.Al-though both catch crops and greenmanure have aneffect on nitrogen loss and its availability for catchcrops,longtermstudiesofcatchcropsandgreenma-nureinthecontextofnutrientdepletionhaveshownthattheycannotimproveaccesstophosphorusandpo-tassiuminpoorersoils(Pedersenetal.,2005;Jensenetal.,2006).Thismaybearesultofsmallerbiomassproductionbycatchcropsonpoorsoils.Nevertheless,it has been shown (Thorup-Kristensen et al., 2003),thatcatchcropsandgreenmanurestakeupsoilPandthusconvertitfrominorganictoorganicform.SomespeciesmayhaveespeciallyhighPuptakecapability,e.g.,byformingparticularlylongroothairs.Uponin-corporationoftheresiduesintothesoiltheplantPisreleasedslowlyand isnotassusceptible to leachingandprecipitationasinorganicPfertilizers.
In 2008, field bean was the most effectivebinderofphosphorusandpotassiumintheexperiment–4.5kgha-1Pand33kgha-1K(Fig.2).Thephospho-rusandpotassiumamountsdidnotchangesignificant-lyandwere1.8–2.1kgha-1Pand10.8–11.6kg ha-1K,accordingly.
Pand21–45kgha-1Kwhengrownascatchcrops,iftheirbiomasswas400to900kgha-1.Biggerbiomassenablesthemtobindmorenutrients.ThelevelsofPandKinaplantdependonspecies,growthstageandpart of theplant.There ismorepotassium inyoungpartsandmorephosphorusinabovegroundpartsthanintheroots.
In2009,fieldbeanhadthelargestbiomass–2160kgha-1(35%wasroots)butpeabiomasswasnotsignificantlysmaller(20%roots).Fodderradish(38%roots) and white mustard (28% roots) had an equalbiomass–1600kgha-1.Winteroil turniphadabio-massof1395kgha-1(40%roots).ThebiomassofItal-ian ryegrass was significantly smaller.Brassicaceae returnedintosoil28–37kgha-1N.Legumesthatareabletobindnitrogenfromtheairaswell,deliverabout67 kgha-1Nintosoil(Fig.3),buttheirdisadvantagewashighseedrateandprice.
TheC:Nratiointhebiomassthatwasploughedtothesoilvariedfrom13(beanandpea)to33(Ital-ianryegrass).Dependingoncroptypeandamountofbiomass,in2009catchcropsreturnedtothenutrientcyclefrom12(Italianryegrass)to51kgha-1K(bean)and7.3kgha-1P(pea).In2009,Italianryegrasswasthe least effective in binding phosphorus (total bio-massonly620kgha-1)–1.6kgha-1P(Fig.4).
In2009,thesulfurlevelsinplantswerealsomeasured. Sulfur is known to have a positive effectonnitrogenuptakeandplantviability.Plantswithsuf-ficient sulfur give bigger yields with better quality.SulfurdeficiencyhasbecomeanimportantfeatureofmostNorthEuropeanarablecroppingsystems,duetothegreatlyreducedsulfuremissionsfromfossilfuels.Sulfur behavesvery similarly to nitrogen in the soilsystem, and it can easily be lost by leaching in theformofsulfate.Fewstudieshavefocusedspecificallyon theeffectsof catchcropson sulfur retentionandavailability(Thorup-Kristensenetal.,2003).
Eriksen andThorup-Kristensen (2002) havefoundthatBrassicaceae species,whichusuallyhaveahighplantSconcentration,showedhighuptakesof22–36kgha-1S,comparedtoonly8kgha-1StakenupbyItalianryegrass.Datafromthecurrentexperimentdoesnotsupporttheseresults.Thebiggestuptakeofsulfurwasbypea7.8kgha-1S.Althoughbeanbio-masswasrelativelylarge,theamountofsulfuruptakewassimilartothatofBrassicaceaecatchcrops.Bio-massfromItalianryegrassreturnedonly1.5kgha-1 S tothesoil(Fig.4).
crops quite early. The growing period for the catchcropswas72days,withatotalsumof602degreesofeffective temperatures, resulting in thebiggest catchcropbiomassforthewholeexperiment.
In 2010, the total biomass of catch crops(abovegroundparts+ roots)added from930(Italianryegrass and rye) to 3550 kg ha-1 (fodder radish) oforganicmattertothesoil.Althoughinpreviousyearswhite mustard produced about the same amount ofbiomassasfodderradish,theresultsweredifferentin2010.Whitemustardisalong-dayplant;ifitissownearly (in the beginning ofAugust), it quickly startsflowering.Floweringreducesrootactivityandnutri-entuptake.
entfromthewheatyieldaftergrowingBrassicaceae catchcrops.In2010,thecatchcropdidnotaffectgrainyieldssignificantly(Fig.7).AnexperimentcarriedoutinSwedenalsoshowedthatthecatchcropdidnotre-duce grain yields significantly in any of the studiedyears(Stenbergetal.,1999).Mulleretal.(1989)foundanegativeeffectofthecatchcroponthebiomasspro-ductionofthefollowingcrop.
Soil ammonium and nitrate N content mayvary greatly, influenced by soil type andmeasuringtimeandcannotbeconsideredareliableindicatorofsoil fertility(Kärblane,1996).ThesoilcannotretainNO3-,whichisthereforesusceptibletoleaching.Catchcrops should be able to bind available nutrients andbiologicallyusablenitrogenshouldnotleachoutdur-ingvegetation-freeperiods.Inallsoilsamples,NO3-N andNH4-Ncontentwaslowwhenmeasured.
Thenitrateandammoniumnitrogencontentthatwasmeasuredwhilethecatchcropsstillgrewwasrelativelysimilarforallthecatchcrops,butwassig-nificantlydifferentforthecontroltreatment.Accord-ing to literature (Thorup-Kristensen,Nielsen, 1998),catchcropsbindsoilnitrogen,whichshoulddecreasemineralnitrogencontent.Conversely,Stenbergetal.(1999)havefoundthatifthegrowthofcatchcropsis
hindered,nitrateconcentrationsat60cmwerehigherthanthoseexpectedinthecatchcroptreatments.Af-tercatchcrops, theconcentrationofavailablesoilNis normally higher in the topsoil layers,with higheramountsof inorganicN in theuppermostsoil layersandlessinthedeepersoillayers(Thorup-Kristensen,VandenBoogaard,1999).Inthecurrentexperiment,catchcropsdidnotdecreasesoilNO3-andNH4-con-tent,comparedtothecontroltreatment(Table2).
Thereducingeffectofacatchcroponnitrate-Nleachingisassociatedwiththeamountofnitrogenaccumulatedinthecatchcrops(Vos,VanderPutten,2004).Macdonaldetal.(2005)havefoundthatcatchcropsaremost likelytobeeffectivewhengrownonfreely drained sandy soils where the risk of nitrateleachingisgreatest.
2. Of all the Brassicaceae catch crops, themosteffectivewerefodderradishandwhitemustard,whichproducedthemostbiomassandthereforedrovemorenutrientsintothesoil.
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