Soil-and-Its-Uses土壤及其利用

SoilandItsUsesOutline:SoilFormationSoilPropertiesErosionSoilConservationLand-Portionoftheworldnotcoveredbywater.Soil-Mixtureofminerals,organicmaterial,livingorganisms,air,andwater.SoilFormationSoilformationbeginswithfragmentationofparentmaterial.母岩-Ancientrocklayerswithrecentdepositsfromlavaorglacialflows.

熔岩或冰河流动Weathering

风化-Factorsbringingaboutfragmentation破碎orchemicalchangeofparentmaterial.MechanicalWeathering

物理风化,原生矿物Resultsfromphysicalforcesreducingsizeofrockparticleswithoutchangingthechemicalnatureoftherock.FreezingandThawingCyclesErosionfromWindandMovingWaterChemicalWeathering

化学风化，次生矿物-Involvesthechemicalalterationofrockinsuchamannerthatitismorelikelytofragmentorbedissolved.Rockfragmentsexposedtoatmospheremayoxidize,orotherwisechemicallychange.Humus-Decayingorganicmaterial.mixedwiththetoplayersofrockparticles,andsuppliessomeoftheneedednutrientstoplants.Increasethewater-holdingcapacityandinorganicnutrientsolubility(acidcond.)createscrumblysoilwhichallowsadequatewaterabsorptionanddrainage.Otherfactorsinfluencingsoilformation:Burrowinganimalsbringnutrientsupfromdeepersoillayers,improvingsoilfertility.PlantrootsBacteriaandFungi(decomposers)1cmsoilformation:15years(warm,humidclimate)tohundredsofyearsSoilPropertiesTexture

质地，矿物质机械组成：

Variousparticlesaremixedinmanydifferentcombination,resultinginsoilclassification.

Determinedbythesizeofsoilparticles.Gravel石砾,d>2mmSand砂粒,0.05-2.0mmSilt粉砂粒,0.002-0.05mmClay粘粒,<0.002mmToomanylargeparticlesleadstoextremeleaching.Toomanysmallparticlesleadstopoordrainage.Soilclassification:Clay粘土Silt淤泥Sand砂土

Loam壤土IdealforagricultureStructure-Referstothewayvarioussoilparticlesclumptogether. 土壤结构：土壤颗粒的空间排列方式及稳定程度，孔隙的分布及结合状况。Howtochange?Measuredby?Friability-Soil’sabilitytocrumble.vs

粘结性，结持性Ingoodsoils2/3oftheintra-soilspacescontainairaftertheexcesswaterhasdrained.Oxygenforrootcellsandsoilorganism.Protozoa,nematodes,earthworms,insects,algae,bacteria,andfungiaretypicalinhabitantsofsoil.SoilProfileSoilProfile

土壤质地剖面形态-Aseriesofhorizontallayersofdifferentchemicalcomposition,particlesize,andamountoforganicmatter.Horizon发生层-Eachrecognizablelayeroftheprofile.OHorizon-Litter-Un-decomposedorpartiallydecomposedorganicmaterial.AHorizon-(Topsoil)Uppermostlayer-containsmostofthesoilnutrientsandorganicmatter.BHorizon-(Subsoil)Underneathtopsoil.Containslessorganicmatterandfewerorganisms,butaccumulatesnutrientsleachedfromtopsoil.-Poorlydevelopedindryareas.CHorizon-Weatheredparentmaterial-verylittleorganicmaterial.RHorizon-BedrockMostcultivatedlandcanbeclassifiedaseithergrasslandorforestsoil.GrasslandSoils-UsuallyhaveadeepAHorizon-lowrainfalllimitstopsoilleaching.Ahorizonsupportsmostrootgrowth.ForestSoils-Topsoillayerisrelativelythin,buttopsoilleachateformsasubsoilthatsupportssubstantialrootgrowth.(Highrainfallareas)SoilErosion土壤侵蚀Erosion–Wearingawayandtransportationofsoil/topsoil

bywindandwater.Floodplain,delta,muddywaterafterstormEffect:leaveadegradedareaandburyvegetationwhereitsettles.Naturalprocessacceleratedbyagriculturalpractice.Worldwide25.4,China5Billiontons/yrMadeworsebydeforestationanddesertification.High-techagriculturalpracticesonpoorlandincreaseerosionandleadtothetransportofassociatedfertilizersandpesticides.Mostcurrentagriculturalareaslosetopsoilfasterthanitcanbereplenished.WinderosionMostcommonindry,treelessareas.Afterdesertification.SoilConservationWhentopsoilislost,fertilityisreducedordestroyed,thusfertilizersmustbeusedtorestorefertility.Raisesfoodcosts,andincreasessedimentloadsinwaterways.Watererosion–controlrunoffConservationPracticesContourFarming-Tillingatrightanglestotheslopeoftheland.Eachridgeactsasasmalldam.StripFarming-Alternatingstripsofcloselysowncropstoslowwaterflow.Terracing-Levelareasconstructedatrightanglestotheslopetoretainwater-goodforverysteepland.WinderosionWindbreaks-Plantingoftreesorotherplantsthatprotectbaresoilfromthefullforceofthewind.TillagePlowinghasmultipledesirableeffects:Weedsandweedseedsareburied/destroyed.Cropresidueisturnedunder-decaysfasterandhelpsbuildsoilstructure.Leached