简介:Excessivenitrogen(N)fertilizerapplicationtowinterwheatisacommonproblemontheNorthChinaPlain.TodeterminetheoptimumfertilizerNrateforwinterwheatproductionwhileminimizingNlosses,fieldexperimentswereconductedfortwogrowingseasonsateightsites,inHuiminCounty,ShandongProvince,from2001to2003.TheoptimumNrateformaximumgrainyieldwasinverselyrelatedtotheinitialsoilmineralNcontent(Nmin)inthetop90cmofthesoilprofilebeforesowing.TherewasnoyieldresponsetotheappliedNatthethreesiteswithhighinitialsoilmineralNlevels(average212kgNha-1).TheaverageoptimumNratewas96kgNha-1forthefivesiteswithlowinitialsoilNmin(average155kgNha-1)beforesowing.ResidualnitrateNinthetop90cmofthesoilprofileafterharvestincreasedwithincreasingfertilizerNapplicationrate.TheapparentNlossesduringthewheat-growingseasonalsoincreasedwithincreasingNapplicationrate.TheaverageapparentNlosseswiththeoptimumNrateswerelessthan15kgNha-1,whereasthefarmers'conventionalNapplicationrateresultedinlossesofmorethan100kgNha-1.Therefore,optimizingNuseforwinterwheatconsiderablyreducedNlossestotheenvironmentwithoutcompromisingcropyields.
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:到环境因素的空间的全体的土壤氮(N)同位素作文和时间的规模和他们的关系的模式说明N周期并且N采购原料,并且是到全球变化的陆上的N周期和它的反应的综合指示物。这研究的目的是:我)15N(15N)在Qinghai西藏的高原上在不同生态系统类型和土壤侧面珍视调查土壤N内容和自然许多的模式;ii)珍视在土壤N内容和土壤15N的模式上检验气候的因素和土壤特征的效果;并且iii)介绍越过生态系统和土壤测试在土壤15N价值和土壤C/N比率之间的关系。土壤侧面沿着二横断在51个地点被取样在长度的1875km和200km分开并且在Qinghai西藏的高原上的森林,草地和大草原里分布式。每个地点被取样从0~40厘米和每件样品的土壤深度的每10厘米为土壤N内容和15N价值被分析。我们的结果比的显示在草地的土壤N和15N价值(040厘米)高得多在荒芜的大草原。当沿着土壤侧面的土壤15N价值的变化不要不是土壤15N价值趋于与土壤深度增加的山草地,低地草地,和适度的大草原在大多数生态系统之中是统计上重要的时,土壤N为每个生态系统与土壤深度减少了。在土壤15N价值和吝啬的年度降水之间的寓言的关系显示土壤15N价值与在荒芜的大草原增加降水直到500公里增加了,然后与越过所有另外的生态系统增加降水减少了。而且,在15N价值之间的寓言的关系和吝啬的年度温度在所有单个生态系统类型存在。土壤N和15N价值(040厘米)随土壤淤泥和泥土内容的增加增加了。而且,大约11的C/N比率的阀值把在土壤15N价值和土壤C/N比率之间的寓言的关系划分了成积极(C/N<11)并且否定(C/N>11)分开,它越过所有生态系统和土壤侧面是有效的。为土壤15N价值的土壤C/N比率的大解释力量建议了那C和N集中,被降水和温度�
简介:PotexperimentswerecarriedouttoestimateN2fixationbyvetch,milkvetch,sicklealfalfaandbroadbeaninpurestandusinga^15N-labelledsoil.Winterwheatwasusedasthenon-fixingcontrol.The15N-labelledsoilusedwaspreparedbygrowingcorn-wheat-cornsuccessivelyonanearlyorganic-matter-freeXiashuloesssupplementedwithadequateamountsof(15NH4)2SO4,P,Kandmicronutrients,thenincorporatingthese15N-labelledplantmaterialsintothesoilaftereachhavest,andallowingtheplantmaterialstobedecomposedaerobicallyfor410dafterincorporationoftheplantmaterialofthethirecrop.The15Nenrichmentofwheatplant-Nvariedslightlywithorgans,withamaximumdifferenceof9.8%,Basedon15NenrichmentofsoilNinferredfromthemeanvalueofthe15Nenrichmentindifferentorgansofwheat79%-91%oftotalNinthetopsand67%-74%oftotalNintherootsoflegumesstudiedwerederivedfromatmosphere.EstimatebyisotopedilutionmethodwasingoodagreementwiththatbytheconventionaldifferencemethodprovidedvaluesobtainedbythelatterwerecorrectedforseedN,andalsowiththatfromthemeasurementofNaccumulatedinthetopsofthelegumes.
简介:Elevatedatmosphericnitrogen(N)depositionhasbeendetectedinmanyregionsofChina,butitseffectsonsoilNtransformationintemperateforestecosystemsarenotwellknown.WethereforesimulatedNdepositionwithfourlevelsofNadditionrate(N0,N30,N60,andN120)for6yearsinanold-growthtemperateforestinXiaoxing’anMountainsinNortheasternChina.WemeasuredgrossNtransformationratesinthelaboratoryusing15NtracingtechnologytoexploretheeffectsofNdepositiononsoilgrossNtransformationstakingadvantageofNdepositionsoils.NosignificantdifferencesingrosssoilNtransformationrateswereobservedafter6yearsofNdepositionwithvariouslevelsofNadditionrate.ForallNdepositionsoils,thegrossNH4+immobilizationrateswereconsistentlylowerthanthegrossNmineralizationrates,leadingtonetNmineralization.Nitrate(NO3-)wasprimarilyproducedviaoxidationofNH4+(i.e.,autotrophicnitrification),whereasoxidationoforganicN(i.e.,heterotrophicnitrification)wasnegligible.Differencesbetweenthequantityofammonia-oxidizingbacteriaandammonia-oxidizingarchaeawerenotsignificantforanytreatment,whichlikelyexplainsthelackofasignificanteffectongrossnitrificationrates.GrossnitrificationratesweremuchhigherthanthetotalNO3-consumptionrates,resultinginabuild-upofNO3-,whichhighlightsthehighriskofNlossesviaNO3-leachingorgaseousNemissionsfromsoils.ThisresponseisoppositethatoftypicalN-limitedtemperateforestssufferingfromNdeposition,suggestingthattheinvestigatedold-growthtemperateforestecosystemislikelytoapproachNsaturation.
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简介:Fivehumicfractionswereobtainedfromauniformly^15N-labelledsoilbyextractionwith0.1molL^-1Na4P2O7,0.1molL^-1NaOH,andHF/HCl-0.1molL^-1NaOH,consecutively,andanalyzedby^13Cand^15NCPMASNMR(crosspolarizationandmagicanglespinningnuclearmagneticresonace).Comparedwiththoseofnativesoilshumicfractionsstudiedasawholecontainedmorealkyls,methoxylsandO-alkyls,being27%-36%,17%-21%and36%-40%,respectively,butfeweraromaticsandcarboxyls(bein14%-20%and13%-90%,respectively),Amongthosehumicfractions,thehumicacid(HA)andfulvicacid(FA)extractedby0.1molL^-1Na4P2O7containedslightlymorecarboxylsthancorrespondinghumicfractionsextractedby0.1molL^-1NaOH,andtheHAextactedby0.1molL^-1NaOHaftertreatmentwithHF/HClcontainedtheleastaromaticsandcarboxyls.Thedistributionofnitrogenfunctionalgroupsofsoilhumicfractionsstudiedwasquitesimilartoeachotherandalsoquitesimilartothatofhumicfractionfromnativesoils.Morethan75%oftotalNineachfractionwasinamidefrom,with9%-13%presentasaromaticand/oraliphaticaminesandtheremainderasheerocyclicN.
简介:ExperimentswerecarriedoutonavegetablefieldwithPekingcabbage(Brassicapekinensis(Lour.)Rupr.),cabbage(Brassicachinensisvar.OleiferaMakinoandnemoto),greencabbage(BrassicachinensisL.),spinach(SpinaciaoleraceaL.)andrape(BrassicacampestrisL.)tostudytheeffectsofNformsandNratesontheirgrowthandnitrateaccumulation.Theresultsindicatedthatapplicationofammoniumchloride,ammoniumnitrate,sodiumnitrateandureasignificantlyincreasedtheyieldsandnitrateconcentrationsofPekingcabbageandspinach.Althoughnosignificantdifferencewasfoundintheyieldsafterapplicationofthe4Nforms,nitrateNincreasednitrateaccumulationinvegetablesmuchmorethanammoniumN.ThevegetableyieldswerenotincreasedcontinuouslywithNrateincrease,andoversupplyofNreducedtheplantgrowth,leadingtoayielddecline.Thistrendwasalsotruefornitrateconcentrationsinsomevegetablesandatsomesamplingtimes.However,asawhole,thenitrateconcentrationsinvegetableswerepositivelycorrelatedwithNrates.Thus,additionofNfertilizertosoilwasthemajorcauseforincreasesinnitrateconcentrationsinvegetables.Nitrateconcentrationsweremuchhigherinroots,stemsandpetiolesthaninbladesatanyNrate.