Soil Aggregate Stability(17)

土壤团聚体的经典文章

98JOURNALOFSUSTAINABLEAGRICULTURE

necessary(1996a)wasandforforclaysomedispersion.ofthesoilsForoftheEmersonthreesoils(1967)studiedthebyWattsetal.minimumclosetotheplasticlimit(PL).However,forothercriticalsoilstheminimumcriticalconcludedwasequaltoorthatmuchhigherthanthePL.Ontheotherhand,Rasiah(1994)greaterthethanmaximumclaydispersionoccurredatsoilwatercontentstheDryingofthesoilincreasessaturation.

tensionornegativepressureinthewater,andcreasingretreatingdryingmoleculescontinues,thenumbermeniscisolubleofpullcontactsmallcompoundspointssuspendedmineralparticlestogether,in-suchatwhichassilica,bondingcarbonates,cantakeplace.Astoareconcentratedintheliquidphase.Thissolutionphaseandcontractsorganicthesethe1986;contactimmediatepoints,vicinitystrengtheningofthecontactsandsolutesareprecipitatedaroundal.,of1992;KemperandLehrschetal.,1987;andBrown,Bullockthe1995).etcohesional.,1988;(KemperandRosenau,1984;Thus,Dexteraetal.,1988;Mullaetpointscolloidsandprecipitationofslightlysolublemineralscombinationaroundofthedepositioncontactsoilagecohesion.betweenDextersoilparticles(1988)andstabilizeOadestheaggregateswhendry,increasingageondevelopmentoccursdryinganddevelopscreatessoiltensilestructure,stressescreating(1993)whichaggregates.addthatinsomesoilsshrink-willeventuallyOndrying,leadshrink-totheCracksiswettest.

appearofwherecracksthealongsoilhasplaneslowoftensileweaknessstrengththuswhichcreatingiswhereaggregates.thesoilwettingOntheothergressivearedevelopmentnothand,entirelyHusseinofreversedandAdey(1995)reportedthatchangesduetostructuralonunitsdryingthroughandthissequentialhysteresisleadstopro-andLehrschetal.(1991),Edwards(1991),Mullaetal.(1992)wet/dryandcycles.Starickatosoilfreezing-thawingBenoit(1995)foundcycles,thatwhilemacro-aggregatePerfectetstabilitydecreasedinresponsecontentstabilityBenoitattheupontimeofthesefreezingcycles.theAggregateal.soil.Lehrschstability(1990b)etal.(1991),dependsfoundanandonincreasesoilwaterinwithfreezingincreasing(1995)observedtimeoffreezingaggregateswaterwasproducedcontentthatatmacro-aggregatestabilitydecreasedStarickalinearlyandgreaterthantheirfreezing.0.20disruptionBullockkgkg onlyet1ifal.the(1988)waterobservedcontentatthatthetweenFreezingaggregatesresultsintheexpansion.

oficecrystalsinporesbe-thebetweenaggregatesparticles,intobreakingsmallerparticle-to-particleaggregates.Duringbonds,thawingandlittleeffectivelysplitting(Kayetal.,micro-aggregates,andtheporescreatedbyexpandingbondingicecollapseexiststheThesoilproperties1985;Bullockisbrokenofupcompactedetal.,andloosened,clays1988).

therebytendtoraisingbeimproveddrainagebyandfrostventilation

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