essa01 06.pdf - find more resources at oneclass.com Soil...

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SoilIntroduction: soil as resourceSOIL IS AN ABSOLUTELY CRITICAL RESOURCE1.EX: Mesopotamian culture decline and fall because of soil salinization.2.EX: Mayan Culture CANADA: 13% cropland; 54% forests and woodlands.CRITICALFUNCTIONS:1.Agriculture/support of plants2.Soil carbon storage  related to climate change.3.EcosystemSoil is a “system”Complex mixture of organic and inorganic component and full of various organisms:1.Bacteria2.Protists3.Fungi4.InvertebratesHow Does Soil Form?WEATHERING1.PHYSICAL (MECHANICAL)Glaciers, temperature change, freezing of water.2.CHEMICALa)Dissolution in acidb)Carbonic acid (H2CO3)c)Plant organic acidsd)Biological effect: bacteria, worms, lichens.Soil Forming Factors1.Climate: faster forming in warm, wet climates2.Organisms3.Topographical relief4.Parent material5.Timefind more resources at oneclass.comfind more resources at oneclass.com
Soil PropertiesSoil Horizons1.O:organic matter deposited by organisms(plants)2.A:top soil, upper mineral horizon mixed withorganicmatter3.B:mineral soil receiving leachate from Ahorizon 4.C:mostly weathered parent material5.R:pure parent materialSoil Characterization1.Colour  largely indicates composition2.Texture  controlled by size of particles3.Structure  indicates the organization or“clumpiness”of soil4.Chemistry: pH; Cation exchange rate.Soil order1.Based on the characterization, we can dividesoil into different soil orders: (different inAmerica and Canada)2.We have podzolic around (forest); find more resources at oneclass.comfind more resources at oneclass.com
Soil texture: related to soil moisture and ground water. Water retain in soil and used byplant by hydrogen bond. (what if the soil made of pure sand? Can it support plantgrowth? How about pure clay?)SoilChemistry: Cation Exchange
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2.More negatively charged surfaces on soil means more positively charged ions canbe held (clay and detritus particles are nagetive).3.Exchange: plant roots donate H+ to soil in return for cation nutrients4.Cation exchange capacity (CEC): expresses a soil’s ability to hold onto cations(i.e., not to be leached out).5.CECis a thus very important fertility parameterProblems Soil are FacingLand class: Class1 Land: flat, fertilized; Class2: fertilized, little slope; Class5: more topography,stones; Class7: not able to do agriculture.SoilDegradation ProblemsIdeal Soil: loamy mixture with neutral pH that is workable and can hold nutrients.1.Erosion2.Desertification3.Salinization4.Waterlogging5.Nutrient depletion6.Structural breakdown7.PollutionBiggest Issue: SOIL EROSION1.Allclimateand soil types2.Most agricultural techniques increase erosion rates by 10-100 X “natural” rates.3.Agentsoferosion: 3.a)Wind: flat, treeless terrainexposure; dependent on texture.3.b)Water: slope and rainfall ratesare critical; increased surface runo

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