Soil Aggregate Stability(15)

土壤团聚体的经典文章

96JOURNALOFSUSTAINABLEAGRICULTURE

dryingeffectcycleshadaneffectonthestabilityofsoil’’Utomowasanddependentartificialaggregates,buttheDexteron(1982)theclaytype.

thetoexplaintheapparentinconsistenciesintroducedthementionedconceptofabove.‘‘equilibriumstatesofhistory,hypothesisstabletherethatforanygivensoilcompositionandphysicalTheyenvironmentintroducedumappropriatevaluemacro-aggregates.isanequilibriumwillincreasetheirSoilsproportion,whichproportionhaveorrangeofproportionsofwaterandlesssoilsthanwhichtheappropriateequilibri-thevaluewilldecreasetheirproportion.Theyalsohaveattributemorethanparttheofbiologicalinconsistenciestothefailuretodistinguishbetweenphysicalandmicro-encesHowever,aggregatingfactors.

aggregateinsoilsomeatsize,type,ofthecontradictoryresultsmayalsoarisefromdiffer-methodordifferencesandrateofwettinginexperimentalconditions,suchassoilexplainingthetimeofsampling.Wewilldiscusssomethesamples,andsoilwatercontenttheExperimentaltheapparentofthesepossiblereasonsforconditionsinconsistencies.

suchasthemethodgregatewettingratesinfluencetheeffectsofwetting-dryingofwettingcyclesandinparticular(Kemperstability.1996a).andRosenau,1986;Aggregateswettedveryslowlywillmaintaintheironmacro-ag-structureslowpletelyenough.However,Duringthewetting,wettingReichertprocessandtheaggregatescanNorton,bemayhighly1994;Amézketaetal.,eitherdisruptivedisintegrateifitiscom-notness(slaking)orremainintactwithonlylooseningatthepointsofweak-uniform(mellowing)shearordifferential(Barzegarhydrationetal.,and1996).Rapidwettingproduces:(1)non-betweenplanes;and(2)airentrapmentinsideswellingcapillaryofthepores.clayfraction,causingplanesdifferentstructuralunitsarestrongenoughtoovercomeWhenthethebondsshearsoil(McKenziematrix,andthereducingpressureofentrappedair,onlymicrocracksareformedintheOades,andDexter,the1985;cohesivenessLeofparticlesandhencethesoilstrengthtainproducesintact.1993;OnandtheBarzegarotherhand,etal.,when1995).Bissonnais,thebondsInthese1989;LeSouderetal.,1991;arecases,theaggregatesmain-smallerapressureexceedingtheircohesivestrength,weakaggregatesandtheentrappedslakeairGäthincreasesandstructuralFrede,units(KemperandRosenau,1986;GrantandDexter,1990;intoduringsoilfriability1995).andMellowingreducesisthedesirableenergyinofagriculturaldraftforcessoilsoftillagebecausetoolsitSomeStabilitycultivationalso(Barzegaretal.,1996).

creasingauthors1990a,soilwaterhavevariescontentfoundwiththatthesoilwatercontentatthetimeofsampling.(Gerard,macro-aggregate1987;Cootestabilityetal.,decreasedwithin-etal.,1994),c;Gollanyandetclayal.,dispersion1991;Rasiahincreasedetal.,1992;withCaron1988;Perfectetal.,increasingetal.,water1992b;content

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