Soil&TillageResearch
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Impactsof9yearsofanewconservationalagriculturalmanagementonsoilorganiccarbonfractionsWangQuanyinga,WangYangb,WangQicuna,LiuJingshuanga,*aKeyLaboratoryofWetEcologyandEnvironment,NortheastInstituteofGeographyandAgroecology,ChineseAcademyofSciences,Changchun130102,ChinabKeyLaboratoryofMollisolsAgroecology,NortheastInstituteofGeographyandAgroecology,ChineseAcademyofSciences,Changchun130102,ChinaARTICLEINFOABSTRACTArticlehistory:
Received9July2013Receivedinrevisedform5May2014Accepted7May2014Keywords:ConservationalagriculturalmanagementsystemConventionalagriculturalmanagementsystemCornLabilesoilorganiccarbonSoilorganiccarbonLabilesoilorganiccarbonpoolsarewidelyregardedasvaluableindicatorsofchangesinsoilCsequestrationpoolsanddynamicsinducedbydifferentsoilmanagementpractices.Theobjectiveofthisstudywastoevaluatehowanewconservationalagriculturalmanagement(NCAM),whichhasbeenprovedtobeaneffectivepatterntoincreasecornyield,affectssoilorganicC(SOC)andlabileSOCpoolsaftera9-yearexperimentinNortheastChina.Narrow-widerow(1.70mwiderowand0.30mnarrowrow,cornissowedinthenarrowrowwithtwolines),no-till,residueretention,changeofridgedirection,andfallowareadoptedforNCAM.Soilunderconventionalagriculturalmanagement(CAM)wasalsostudiedtobeasacomparison.Soilsamplesweretakenfrom0–20to20–40cmdepths.TheresultsshowedthatnosignificantdifferencewasfoundforSOCbetweenthetwomanagementsforbothdepths,indicatingthatSOCisatoogrossmeasurement.SoillabileorganicCfractions:microbialbiomassC,hot-waterextractableorganicCandpermanganateoxidizableC(KMnO4–C)contentsweresignificantlyhigherunderNCAMcomparedtoCAMforbothdepths,reflectingthebuild-upoflabileCpoolsunderNCAM.Inaddition,ofthethreeCfractions,KMnO4–CwasthemostsensitiveindicatorofchangesinSOCinducedbydifferentagriculturalmanagementregimes.OurresultsimpliedthattheapplicationofNCAMisimportanttosoilCsequestrationandimprovingsoilquality.ß2014ElsevierB.V.Allrightsreserved.1.IntroductionItiswidelyknownthatthehighlevelsofsoilorganicC(SOC)arelinkedtotheimprovementsofnutrientsupplytocrops.Thus,theenhancementofSOCinagriculturalsoilscouldnotonlyimprovesoilqualitybutalsocouldincreasecropproductivity(Lal,2004).SoilmanagementsystemscanaffectSOCintheagriculturalecosystem(Planteetal.,2006).However,itisdifficulttodetectthechangesintotalSOCintheshort-andmedium-termbecauseofthelargebackgroundamountsofrelativelystableSOC(Gregorichetal.,1994).Meanwhile,SOCisrecognizedtoconsistofvariousfractionsvaryingindegreeofdecomposition,recalcitrance,andturnoverrate.LabileSOCpoolsarevaluableindicatorsofearlychangesinSOCstocks,and(hence)changesinsoilCsequestrationpoolsanddynamicsinducedbychangesinsoilmanagementpractices(Haynes,2000;Weiletal.,2003).Thus,itwouldbeusefuliflabileSOCfractionsareidentified.Additionally,sincesoilisa*Correspondingauthor.Tel.:+8643185542296;fax:+8643185542298.E-mailaddress:liujingshuang@neigae.ac.cn(J.Liu).http://dx.doi.org/10.1016/j.still.2014.05.0040167-1987/ß2014ElsevierB.V.Allrightsreserved.complexsystem,themeasurementofasinglelabileSOCfractiondoesnotadequatelyreflectmanagement-inducedchangesinsoilquality.SoilmicrobialbiomassC(SMBC),hot-waterextractableorganicC(HWEOC)andpermanganateoxidizableC(KMnO4–C)havebeenwidelyrecognizedaslabileSOCpoolsandimportantindicatorsofsoilquality(Ghanietal.,2003;Chenetal.,2009).SMBC,asthelivingcomponentofsoilorganicmatter(SOM),hasplayedacriticalroleinnutrientcyclingandSOMdecompositionandtransformation.ThehotwaterextractionmethodisthoughttoextractthesolubleorganicCwhichoriginatesfromsoilmicrobialbiomass,rootexudates,andlysates(Ghanietal.,2003).KMnO4oxidationsimulatesmicrobialdecomposition,andthereforeKMnO4–CpartlyreflectstheinsituenzymaticdecompositionoflabileSOM(Loginowetal.,1987).The‘‘JilinCornBelt’’(408–428N,1258–1288E)coversanareaof60,000km2,andithasplayedaveryimportantroleinfoodsupplyinChina.ThesustainabilityofagricultureinthisregioncouldaffectChina’sfoodsecurity.Soilhasbeenintensivelyusedinanimproperwayinthisareasincethereclamation,especiallyinthelatest50years,i.e.conventionalagriculturalmanagement(CAM)(Yangetal.,2003).Underthiscultivationsystem,tillageandresidue2Q.Wangetal./Soil&TillageResearch143(2014)1–6improvedunderstandingoftheeffectsofNCAMonsoilquality,researchesaboutSOCpoolsareneeded.TheobjectivesofthisstudyweretoinvestigatetheeffectsofNCAM(aftera9-yearperiod)onlabileSOCpoolsincludingSMBC,HWEOC,andKMnO4–C,andtheirsensitivitytomanagement-inducedchanges.Forcomparison,theeffectsofCAM,whichisadominantagriculturalmanagementinthisarea,onlabileSOCpoolswerealsostudied.2.Materialsandmethods2.1.SiteinformationThisstudywasconductedattheAgriculturalExperimentStationofBlackSoil(448120N,1258330E),NortheastInstituteofGeographyandAgroecology,ChineseAcademyofSciences,DehuiCounty,JilinProvince,China.Themeanannualtemperatureis4.48C,andthemeanannualprecipitationis520mm.ThesoilisclassifiedasMollisolsaccordingtoUSDASoilTaxonomy,withamollicepipedon0–50cm.Theaveragesoiltexturewas36.0%clay,24.5%siltand39.5%sand.Inthespringof2004,partofthefieldunderCAMwasconvertedtoNCAM.TheareaofCAMandNCAMis10,000m2,respectively.CornissowninAprilandharvestedinSeptember.Afterharvest,thecornstrawkeeps30–35cmstubblestandforCAMandNCAM.TheCAMincludestheprocessesoftillageandremoveofcropresidues.Thetillagetreatmentisperformedbyastubblecleaner,andthistoolissimilartoashallowploughbutundercutsandmixesonlytheuppersoillayer(10cm).TomaketheridgedirectioncoincidencewiththedirectionofsunlightradiationinsummerinDehuiCounty,theridgedirectionwaschangedfromthenorth-southtothesouth-west20degreesunderNCAM.A‘‘30cm+170cm’’narrow-widerowwasadoptedfortheNCAM.UnderNCAM,thesoilisvirtuallyleftundisturbedexceptfortheopeningwheretheseedisplaced.TheresidueretentionisperformedforNCAM,andthecornstrawisjustleftinthenarrowrowsasawhole.UndertheCAM,thedistancebetweentheplantsis25cm,whilethedistanceis16.7cmunderNCAM.Thus,thenumbersofthecornareboth6.4plantsmÀ2forthetwodifferentmanagements.Thecornisplantedwithself-madeno-tillplanterunderNCAM.TheapplicationratesofN,PandKarethesameforthetwomanagements.Eachyear,N,PandKfertilizerswereappliedtocornat100,45.5and78kghaÀ1respectivelyasstarterfertilizers.Thetypesofthesefertilizerswereurea,ammonium,dibasicphosphate,andpotassiumsulfate.Addition-al,50kgNhaÀ1wastopdressedatthesixthleafstageofmaize.MorespecificinformationaboutNCAMcanbefoundinTable1andFig.1.2.2.SoilsamplingSoilsampleswerecollectedfromtwodepths(0–20and20–40cm)inOctober2012.ThreetillagerotationcycleshavefinishedfortheNCAM.TwelvesoilsampleswerecollectedfromeachFig.1.Thesketchesoftheconventionalagriculturalmanagementandthenewconservationalagriculturalmanagement.(a)conventionalagriculturalmanagement;(b)newconservationalagriculturalmanagement.Underthenewconservationalagriculturalmanagement,theridgedirectionisthesouth-west15–20degrees,anda2.0msuperwiderowisadopted.Thesuperwiderowiscombinedbyawiderowwithadistanceof1.7mandanarrowrowwithadistanceof0.3m.Thewiderowisseparatedintofiveparts,with37cmforparts2,4and6,while30cmforparts3and5,respectively.Thecornissowninpart1withtwolinesforthefirstyearandtherestpartsareleftfallow.Then,thecornissowninparts3and5forthesecondyearandthethirdyear,respectively.Forthefourthyear,thecornissowninpart1again.Thus,therotationcycleperiodisthreeyearsforthenewconservationalagriculturalmanagement.removalpracticesareadopted.Consequently,thisagriculturalstrategyhasresultedinseriousenvironmentalproblems,suchasthedecreaseofSOCcontent(Wangetal.,2007).Inordertomakethecornutilizethesunlightfullyduringthegrowthandtoincreasecropyieldsinthisarea,wehaveproposedanewconservationalagriculturalmanagement(NCAM).UnderNCAM,narrow-widerow,no-till,residueretention,changeofridgedirection,andfallowareadopted(Fig.1;Liuetal.,2006).Accordingtotheresultsofa9-yearfieldexperiment,thecornyieldhasincreasedabout15–17%undertheNCAMcomparedtotheCAM.BecauseSOMisanimportantindicatorofsoilfertilityandproductivity,themaintenanceofSOCisnecessaryforsustainableagroecosystems(Gregorichetal.,1994;Haynes,2005).ManystudieshaveindicatedthatvarioustillagesystemshavedifferenteffectsonSOC,dependingonregionalclimate,soiltype,residuemanagementpractice,andcroprotation(Chanetal.,2002;PugetandLal,2005;Qinetal.,2010).Moreover,thedifferencesinamountsoflabileorganicCfractionsresultingfromdifferentmanagementpracticescanprovidevaluableinformationaboutmechanismsofCsequestration(Sixetal.,2002).Hence,foranTable1Plantingpatternsofthetwoagriculturalmanagements.CAM,conventionalagriculturalmanagement.NCAM,newconservationalagriculturalmanagement.RowspacingCAM65cmRowdirectionNorth–southResidueretentionTillageWithoutcropresiduesNotillRotationPlantdistanceTillage(mixesonlytheupper20cmlayer)Rotation(therotationcycleperiodisthreeyears)16.7cm(6.4plantsmÀ2)Meancornyield(kghmÀ1yearÀ1)No25cm(6.4plantsmÀ2)8500NCAM‘‘30cm+170cm’’narrow-widerowSouth–west20degreeResidueretention(thecornstrawisjustleftinthenarrowrowsasawhole)11,000Q.Wangetal./Soil&TillageResearch143(2014)1–63
agriculturalsystemusingtheSystematicGridSamplingMethod.Eachsamplewasacompositeofsixsubsamples.Soilsubsamplesweretakenfromthemiddleofthenarrowrowsatdepthsof0–20and20–40cm.Subsampleswerebulkedtomakeacompositesoilsample(approximately1kg).Soilsamplesweredividedintotwoportions.Oneportionwasair-dried,groundwithwoodenblocksandpassedthrougha2-mmsieveforphysicalandchemicalanalysis,andtheremainingportionwassievedthrougha2-mmsieveandfrozenforbiochemicalanalysis.2.3.Analysisofsoilproperties2.3.1.SoilorganiccarbonTotalSOCwasdeterminedbyK2Cr2O7oxidationat170–1808Cfollowedbytitrationwith0.10molLÀ1FeSO4.2.3.2.LabilesoilorganiccarbonfractionsSoilmicrobialbiomassCwasanalyzedbythefumigationextractionmethod(Vanceetal.,1987).Eachreplicatewasdividedintotwoequivalentportions.Oneportionwasfumigatedfor24hwithethanol-freechloroformandtheotherportionwasastheunfumigatedcontrol.Bothfumigatedandunfumigatedsoilswereshakenfor30minwith0.50molLÀ1K2SO4(1:4soil:extractionratio).CarbonintheextractswasdeterminedimmediatelyafterextractionusinganautomatedtotalorganicCanalyzer(MultiN/C3000,AnalyticJena,Germany).Hot-waterextractableorganicCwasdeterminedbyamodifiedmethodofGhanietal.(2003).Briefly,10goffreshsoilswereextractedwith40mlofdistilledwaterin50mlpolypropylenecentrifugetubes.Thetubeswereshakenfor30minonanend-over-endshakerandthenwereleftinahot-waterbathfor18hat808C.Thetubeswerethenshakenfor10mintoensurethattheextractedCwasfullysuspended.Thetubeswerecentrifugedfor15minat8000revminÀ1,andthesupernatantswerevacuumfilteredthrough0.45mmfilters.ExtractswereanalyzedfortotalorganicContheMulti3000N/CtotalorganicCanalyzer(AnalytikJena,Germany).EasilyoxidizableCwasexpressedasKMnO4–C.TheKMnO4–CwasdeterminedaccordingtothemethoddevelopedbyVieiraetal.(2007).Finelygroundair-driedsoilsamples(equivalentto15mgofSOC)wereoxidizedby25mlof333mmolLÀ1KMnO4.Thesuspensionswerehorizontallyshakenat60revminÀ1for1handcentrifugedat2000revminÀ1for5min.Thesupernatantsweredilutedandmeasuredat565nmwithaspectrophotometer.Allsoilsampleswereanalyzedintriplicate.2.4.CalculationsandstatisticalanalysisTheSensitivityIndex(SI)wascomputedusingthefollowingformula,accordingtoBangeretal.(2010):CfractioninsoilofagiventreatmentÀCfractioninSI¼referencesoilCfractioninreferencesoilTheSIwasusedtocomparethemagnitudeofchangesindifferentlabilesoilorganiccarbonCfractionrelativetothereferencesoil.ThesoilunderCAMwasusedasareferencesoilinthisstudy.AllstatisticalanalyseswerecarriedoutwiththeprogramSPSS16.0forWindows.Differencesinsoilpropertiesbetweendifferentdepthsordifferentmanagementsweretestedbymeansofaone-wayanalysisofvariance(ANOVA).FisherLeastSignificantDifference(LSD)testwasperformedtodeterminesignificantdifferencesamongthesites.Statisticalsignificanceisacceptedwhentheprobabilityoftheresultassumingthenullhypothesis(p)islessthan0.05.Table2SoilorganicC(gkgÀ1)for0–20and20–40cmdepthsundertheconventionalagriculturalmanagement(CAM)andthenewconservationalagriculturalmanage-ment(NCAM).ManagementCAMNCAM0–20cm18.6aA19.3aA20–40cm16.3aB16.4aBMeanvaluesbydifferentlowercaselettersinthesamelinearesignificantly(p<0.05)differentbetweenmanagements,andmeanvaluesbydifferentcapitallettersinthesamecolumnaresignificantly(p<0.05)differentbetweentwodepths.3.Results3.1.SoilorganiccarbonTheeffectsofdifferentmanagementsonSOCareshowninTable2.At0–20cm,SOCcontentdidnotdifferbetweenthemanagements,withvaluesvaryingfrom18.6to19.3gkgÀ1.Thesimilartendencywasalsofoundforthe20–40cmdepth,withvaluesvaryingfrom16.3to16.4gkgÀ1.Inaddition,higherSOCcontentsinthesurfacesoil(0–20cm)ascomparedtosubsurfacesoil(20–40cm)werefoundforboththetwomanagements.3.2.LabilesoilorganiccarbonfractionsThedifferentagriculturalmanagementssignificantlyaffectedsoillabilesoilorganicCfractionsat0–20cmand20–40cmdepths(Fig.2).AverageconcentrationsofSMBC,HWEOCandKMnO4–Cdecreasedwithsoildepthforbothmanagementsrespectively.Furthermore,allSMBC,HWEOCandKMnO4–CvaluesweresignificantlylowerunderCAMthanthatunderNCAM.SMBCvaluesvariedfrom415.3mgkgÀ1(0–20cm)to267.5mgkgÀ1(20–40cm)forCAM,andfrom480.8mgkgÀ1(0–20cm)to350.0mgkgÀ1(20–40cm)forNCAM,respectively.TheHWEOCvalueschangedfrom336.4mgkgÀ1(0–20cm)to216.8mgkgÀ1(20–40cm)forCAM,andfrom485.0mgkgÀ1(0–20cm)to317.9mgkgÀ1(20–40cm)forNCAM,respectively.TheKMnO4–Cvaluesvariedfrom3.17gkgÀ1(0–20cm)to1.38gkgÀ1(0–20cm)forCAM,andfrom7.31gkgÀ1(0–40cm)to6.55gkgÀ1(0–40cm)forNCAM,respectively.3.3.IndicesofsensitivityofthelabilecarbonfractionstomanagementchangesTheSIvaluesfortheKMnO4–Cwere0.65and4.23for0–20cmand20–40cmdepths,andthevaluesforHWEOCwere0.08and0.94for0–20cmand20–40cm,whilethevaluesforSMBCwere0.16and0.31for0–20cmand20–40cm,respectively(Table3).4.DiscussionThesitesusedforthisstudyhadthesamemanagementpriortotheestablishmentofNCAM,andthusthesoilsunderCAMandNCAMaredevelopedfromthesameparentmaterial.Assuch,differencesinsoillabileorganicCfractionsamongthesitesareassumedtobetheresultsofdifferentagriculturalmanagements.4.1.EffectsofmanagementsonsoilorganiccarbonTherewasastrongdepth-dependencyofSOCcontentsunderthetwomanagements.HigherSOCcontentsinthetopsoilsofthetwomanagementsmaybeexplainedbythefactsthatSOCcontentsarestronglyrelatedtorootCinputsandcropresiduesareoftenaccumulatedinthesurfacesoils(Qinetal.,2010).NumerousstudieshavereportedthegreaterstorageoforganicCinsoilsunder4Q.Wangetal./Soil&TillageResearch143(2014)1–6Fig.2.Labilesoilorganiccarbon:(a)soilmicrobialbiomassC,(b)hot-waterextractableorganicC,and(c)permanganateoxidizableC(KMnO4–C),asaffectedbydifferentmanagementsat0–20and20–40cmdepths.CAM,conventionalagriculturalmanagement;NCAM,newconservationalagriculturalmanagement.Errorbarsrepresentstandarddeviation.Valuesfollowedbydifferentlowercaseletterswithinthesamedeptharesignificantlydifferentbetweenmanagements(p<0.05).no-tillthanintilledsoils,especiallywithdifferencesintillageintensityandresidueretention(Sixetal.,2004;Wrightetal.,2005).However,thetotalSOCcontentdidnotdifferbetweenCAMandNCAMforbothdepthsinthisstudy.Infact,tillagesystemsdonotusuallyproducesignificantchangesintotalSOC.ChangestothequantityoftotalSOCgenerallyoccurslowly(oftheorderofseveraldecades)unlessthesoilissubjecttoseveredisturbancesuchasintensivetillageorerosion(Mann,1986).Inaddition,thetillagetreatmentforCAMinthisstudyisregardedasonepatternofthereduced-till,andtheeffectsoftillageonthetotalSOCmaybelimited.Moreover,thelackofasignificantimpactofsurfaceresiduesontotalSOChasalreadybeenreportedbyHaronetal.(1998),andSOCmaybeinfluencedtoagreaterextentbyrootmaterialratherthansurfacelitterintheshort-ormedium-termcultivation.Thus,therateoforganicCadditionviastrawmaybeinsufficienttoinduceasufficientchangeinthetotalSOCpoolwithin9yearsunderthelocalclimaticcondition.Ontheotherhand,smallchangesintotalSOCcanbedifficulttomeasureintheshorttomediumterm(uptoseveralyears)duetonaturalvariability,andchangeinmanagementismorelikelytoaffectlabilefractionsofSOMintheshorttomediumterm(Powlsonetal.,1987).Therefore,thepotentiallong-termimpactsofNCAMafter9yearscultivationaredifficulttoquantifyusingSOConly.4.2.EffectsofmanagementsonlabilesoilorganiccarbonfractionsThelabileorganicCfractionsonlyaccountforasmallfractionofSOM,butareusedbythesoilmicrobialcommunityasanenergysourceformetabolicactivity(Janzenetal.,1992).RelativesizesoflabileorganicCpoolsinvariousecosystemsandtheirresponsestodisturbancecouldhaveimportantimplicationsinunderstandingSOCstability.Also,identificationofsuchfractionsmayserveasanindicatororevenasaverificationtoolforSOCchangesintermsofaccountingforCstocks(Chanetal.,2002;Yangetal.,2009).IthasbeenwidelyacceptedthatconservationmanagementpracticeslikenotillandcropresiduemulchcouldincreaselabileorganicCintheuppersoilprofile(Jacobsetal.,2009,2010).Inthisstudy,thevaluesofSMBC,HWEOCandKMnO4–CalsorevealedacleardeclinewithsoildepthnotonlyforNCAMbutalsoforCAM.GreaterlabileorganicCfractionsinthesurfacelayercanbeattributedtotheincorporationofcroprootand/orcropresiduesTable3SensitivityindexofthelabilesoilorganicCfractionsfor0–20and20–40cmdepthsunderthenewconservationalagriculturalmanagement.Management0–20cm20–40cmSMBC0.16a0.31aHWEOC0.08b0.94bKMnO4–C0.65c4.23cSMBC,soilmicrobialbiomassC;HWEOC,hot-waterextractableorganicC;KMnO4–C,permanganateoxidizableC.Meanvaluesbydifferentlowercaselettersinthesamelinearesignificantly(p<0.05)differentbetweendifferentparameters.Q.Wangetal./Soil&TillageResearch143(2014)1–65
(Galeetal.,2000;Murageetal.,2007).Inthisresearch,higherSMBC,HWEOCandKMnO4–Cvaluesatthe0–20and20–40cmdepthsunderNCAMcomparedtoCAMwerefound,reflectingtheimpactofdifferentagriculturalmanagementpractices.ThefirstexplanationofthedifferencesbetweenCAMandNCAMistheresultoftillagepractices(Chenetal.,2007).FrequenttillageunderCAMmaybreakdownaggregatesandexposesprotectedorganicmattertomicrobialdecomposition,therebyincreasinglossoflabileorganicC.AsecondexplanationemergesfromthedifferentquantityofresiduesretainedbetweenCAMandNCAM.PlantresiduemightenterthelabileorganicCpools,providesubstrateforsoilmicroorganisms,andcontributetotheaccumulationoflabileorganicC.Inaddition,residuemulchinNCAMsystemcanimprovesoilphysicalandchemicalqualitythroughincreasedinfiltration,aggregatestability,thusaffectthechangesinsoillabileorganicCfractions(Govaertsetal.,2007).Therefore,ourresultsindicatedthattheapplicationofNCAMcanhavebeneficialeffectsonthebuild-upoflabileCpoolsbothatthetopandthesubsurfacelayerswhencomparedtotheCAM(Chenetal.,2009).Inaddition,sinceSMBC,HWEOCandKMnO4–Caresensitivetothedifferentmanagementpracticesandarealsoimportantparametersofsoilhealth,theycanbeimportanttoolsindeterminingthesustain-abilityofagroecosysteminthisstudy.4.3.SensitivityoflabileorganiccarbonfractionsforevaluatingchangesinsoilorganiccarbonTheresultsofpresentstudyshowthatSMBC,HWEOCandKMnO4–CaresensitiveindicatorsofdetectingchangesinSOCafteraperiodof9-yearcultivationunderNCAM.However,themagnitudeofchangesinthelabileorganicCfractionsdifferedfromeachother.Comparisonofthesensitivitytomanagementchanges,KMnO4–CisprovedtobeamoresensitiveindicatoroftheeffectsofsoilmanagementonSOCthanHWEOCandSMBCinthisstudy.Blairetal.(1995)havealreadyshownthattheKMnO4–CismoresensitivetoconversionfromgrasslandtoarableagriculturethantheotherlabileorganicCfractions.ThelowersensitivityofSMBCandHWEOCcomparedtoKMnO4–Cmightbeduetotheirsmallersizes,highlylabilenature,andthemobility(Janzenetal.,1992;Chenetal.,2009).5.ConclusionsAlthoughnosignificantdifferencewasfoundfortotalSOCbetweenNCAMandCAMforboththe0–20cmand20–40cmdepths,theNCAMcouldleadtoincreasesinsoillabileorganicCfractionsaftera9-yearperiodofcultivationcomparedtotheCAM.Moreover,amongthethreelabileorganicCfractions,KMnO4–CwasthemostsensitivefractiontotheapplicationofNCAM.Therefore,NCAMisaneffectiveoptionforincreasingcropyieldandmaintainingsoilsustainabilityin‘‘JilinCornBelt’’.Acknowledgements
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