简介：TocomparethedevelopmentofphysicalcrustsinthreetypicalcultivatedsoilsofChina,ablacksoil(LuvicPhaeozem),aloesssoil(HaplicLuvisol),andapurplesoil(CalcaricRegosol)werepackedinsplashplateswithcoveredanduncoveredtreatments,andexposedtosimulatedrainfall.Meshescoveredabovethesurfacesofhalfofsoilsamplestosimulatetheeffectsofcropresidueoncrusting.Theresultsindicatedaprogressivebreakdownofaggregatesonthesoilsurfaceasrainfallcontinued.Thebulkdensityandshearstrengthonthesurfaceofthethreesoiltypesincreasedlogarithmicallyasrainfalldurationincreased.Duringthefirst30minofsimulatedrainfall,thepurplesoildevelopeda7-8mmthickcrustandtheloesssoildevelopeda3-4mmthickcrust.Theblacksoildevelopedadistinguishable,butstillunstable,crustafter80minofsimulatedrainfall.Soilorganicmatter(SOM)content,themeanweightdiameter(MWD)ofsoilaggregates,andsoilclaycontentwerenegativelycorrelatedwiththerateofcrustformation,whereasthepercentageofaggregatedispersion(PAD),theexchangeablesodiumpercentage(ESP),andthesiltandsandcontentswerepositivelycorrelatedwithcrusting.Mechanicalbreakdowncausedbyraindropimpactwastheprimarymechanismofcrustformationintheblacksoilwithmorestableaggregates(MWD25.0mm,PAD3.1%)andhigherSOMcontent(42.6gkg~(-1)).Slakingandmechanicaleluviationweretheprimarymechanismsofcrustformationinthepurplesoilwithlowclaycontent(103gkg~(-1)),cationexchangecapacity(CEC,228mmolkg~(-1)),ESP(0.60%),andSOM(17.2gkg~(-1)).MechanicalbreakdownandslakingwerethemostimportantintheloesssoilwithlowCEC(80.6mmolkg~(-1)),ESP(1.29%),SOM(9.82gkg~(-1)),andhighPAD(71.7%)andMWD(4.6mm).Simulatedresiduecoverreducedcrustformationinblackandloesssoils,butincreasedcrustformationinpurplesoil.

简介：PhyllostachyspraecoxC.D.ChuetC.S.Chao,afavoredbambooshootspecies,hasbeenwidelyplantedinrecentyears.Fourstandswithdifferenthistoricalmanagementpracticeswereselectedforthisstudytounderstandtheevolutionofsoilmicrobialecologybydeterminingtheeffectsofanewmulchingandheavyfertilizationpracticeonsoilqualityusingmicrobiologicalparameters.Comparedwiththetraditionalpractice(index1),microbialbiomasscarbon(MBC)andsoilmicrobialrespirationcarbon(MRC)withthenewmanagementpracticesignificantlydecreased(P＜0.01andP＜0.05,respectively)with1-2yearsofmulching(index2)andthenforcontinuedmulchingsignificantlyincreased(P＜0.05).TheratiosofMBC/TOC(totalorganiccarbon)andMRC/TOCalsosignificantlydiminished(P＜0.05)withmulching.Theaveragewellcolordevelopment(AWCD)andShannonindexdecreasedwithmulchingtime,andthesignificantdecrease(P＜0.05)inShannonindexoccurredfromindex2toindex3.Theresultsfromaprincipalcomponentsanalysis(PCA)showedthatthescoresofthefirstprincipalcomponentforindexes1and2weresignificantlylarger(P＜0.05)thansoilsmulched3-4yearsor5-6years.Also,thesecondprincipalcomponentscoresforindex1werelargerthanthoseforindex2,suggestingthattheabilityofsoilmicroorganismstoutilizesoilcarbonwasdecreasingwithlongeruseofthenewmanagementpracticeandcausingadeteriorationofsoilbiologicalproperties.

简介：在在哈萨克斯坦的南部的部分的Arys西域运河命令区域的荒谬的灌溉惯例与差的物理、化学的性质导致了土壤的形成。为了学习灌溉和沥滤的惯例或地下水上升是否在阳离子上贡献了Mg2+的累积，交换这些土壤的建筑群，当来源数据和视觉MINTEQ模型被使用在学习区域分析水和土壤的化学作文，在土壤和地下水质量的历史的变化被使用。强加的灌溉政体并且轻sierosem土壤沥滤导致了溶解并且从土壤侧面的固有的石膏和有机物的随后的沥滤。进一步，灌溉水里的酸式碳酸盐的支配支持了象方解石在场的碳酸盐矿物质捱过。与灌溉水里的Ca2+相比的Mg2+的更高的集中在阳离子交换建筑群上由Mg2+导致了Na+的代替。在命令区域的更低的部分，浅地下水在阳离子交换地点上贡献了Na+并且到Mg2+的大程度的累积。