简介：Changesofsoilorganicnitrogenformsandsoilnitrogensupplyundercontinuousricecroppingsystemwereinvestigatedinalong-termfertilizationexperimentinJinhua,ZhejiangProvince,China.ThefertilizertreatmentsincludedcombinationofP-K,N-K,N-P,andN-P-Kaswellasthecontrol.Aftersixyearsofcontinuousdouble-ricecropping,totalsoilNandhydrolysableNcontentsremainedstableinplotswithNtreatments,whilethehydrolysableNcontentsweresubstantiallyreducedinthoseplotswithoutNapplication.Comparedtotheunbalancedfertilizationtreatments,PandKincreasedthepercentageofhydrolysableammoniumNinthetotalsoilNwiththebalancedapplicationofN,andalsomaintainedhigherricegrainyieldsandnitrogenuptake.GrainyieldwaspositivelycorrelatedwithtotalNuptake(r=0.875**),hydrolysableN(r=0.608**),hydrolysableammoniumN(r=0.560**)andthehydrolysableunknownN(r=0.417**).TotalNuptakewaspositivelycorrelatedwithhydrolysableN(r=0.608**),hydrolysableammoniumN(r=0.440**)andhydrolysableunknownN(r=0.431**).Soilnutrientdepletionand/orunbalancedfertilizationtoricecropreducedNcontentinsoilmicrobialbiomass,andthereforeincreasedC/Nratio,suggestinganegativeeffectonthetotalmicrobialbiomassinthesoil.

简介：Soilqualityassessmenthasbeensuggestedasaneffectivetoolforevaluatingsustainabilityofsoilandcropmanagementpractices.Theobjectiveofthisstudywastodevelopasensitivesoilqualityindex(SQI)basedonbulkdensity(BD),water-holdingcapacity(WHC),water-stableaggregates(WSA),aggregatemeanweightdiameter(AMWD),totalorganicC(TOC)andCinputtoevaluatetheimportantrice-wheatcroppingsystemonanInceptisolinIndia.Along-termexperimenthasbeenconductedfor18yearsattheIndianCouncilofAgriculturalResearch-IndianInstituteofFarmingSystemsResearch,Modipuram,India.Thetreatmentsselectedforthisstudywerecomprisedofano-fertilizercontrolandN,PandKfertilizers(NPK)combinedwithZnandSfertilizers(NPK+Zn+S),farmyardmanure(NPK+FYM),greengramresidues(NPK+GR)andcerealresidues(NPK+CR),laidoutinarandomizedcompleteblockdesignwiththreereplications.SoilsampleswerecollectedandanalyzedforBD,WHC,WSAandTOC.Correlationanalysisrevealedthatbothriceandwheatyieldssigni?cantlyincreasedwiththeincreasesinAMWD,TOCandCinput,butdecreasedwiththeincreaseinBD.TheSQIvalueswerethengeneratedbasedonregressionanalysisofBD,WSA,AMWD,TOCandCinputwithriceandwheatyieldsforthe0–15and15–30cmsoillayers,respectively.RegressionanalysesbetweencropyieldsandSQIvaluesshowedaquadratictypeofrelationwiththecoeffcientofdetermination(R~2)varyingfrom0.78to0.89.Withregardtosoilsustainability,applyingcropresiduestobothriceandwheatcouldmaintainsoilqualityforalongerperiod,whereasthehighestyieldsofboththecropswererecordedintheNPK+Zn+Streatment.Theregressionequationsdevelopedinthisstudycouldbeusedtomonitorsoilqualityinasubhumidtropicalrice-wheatcroppingsystem.