9.2 SOILS Where the geoshpere and the bioshpere meet

Learning Targets 1.Discuss why soil is an important resource 2.Describe how soil forms from existing rocks 3.Describe the different textures and components of soil 4.Draw and describe a soil profile 5.Define 3 climate related soils: pedalfer, pedocal, and laterite.

Soils – Characteristic #1 Composition varies with climate a)Most important factor determining soil b)Deserts 100% inorganic c)Swamps 100% organic

Soils – Characteristic #1 Increased weathering  greater soil formation a)More rain  more chemical reactions b)Increased rainfall  Increase dissolved rock c)Increased temperature  Increase rate of chemical reactions d)Warmer regions  Faster plant & bacteria growth

Soils – Characteristic #2 Inorganic matter a)50% of most soils b)Sediments, water, air c)Determines porosity  drainage

Soils – Characteristic #3 Organic matter – Biological Activity a)50% of most soils b)Humus: rotting remains of dead organisms c)Increases water holding ability d)Increases fertility

Soils – Characteristic #4 Home to millions of species

Up to 3 billion organisms/gram

Soil Formation - Overview 1.Depends on: a)Climate: determines temperature, precipitation, and type of vegetation b)Source rock: determines type of inorganic material c)Topography: determines rate of erosion d)Local organisms: can speed up or slow down the process; determines type of organic matter

Identifying Soils Texture triangles are used to identify soil a)% sand b)% clay c)% silt d)Mixture of all 3 types  loam

Soil profiles As bedrock breaks down, layers of soil form: a)Horizon: one layer of soil b)Profile: all horizons from bedrock to topsoil

Soil profile 1.Depth varies widely from place to place 2.A Horizon a)Topsoil: organic matter, humus, roots, organisms 3.B Horizon a)Subsoil: clay, aluminum, iron 4.C Horizon a)Source rock: bedrock beginning to weather

Climate Related Soils 1.Every climate type has an associated soil 2.Most common climate related soils a)Pedalfer b)Pedocal c)Laterite

Pedalfer 1.Forests: a lot of rain 2.Trees that lose leave annually a)Deciduous trees 3.Al and Fe rich  ped-Al-Fe-r 4.Fertile 5.High clay content

Pedocal 1.Grasslands: dry seasons 2.Calcium rich  pedo-Cal 3.Less fertile 4.Low clay content 5.Soil forms very slowly; Why? a)Less vegetation and no annual leaf loss means less organic matter

Laterite 1.Tropical areas: hot, humid 2.Low nutrient content a)Nutrients get dissolved by constant rain 3.Very thick, but not very fertile

PedalferPedocalLaterite

Soil Conservation 1.Maintain plants a)Protects from wind and water erosion b)Provides organic matter 2.Good farming practices a)Low-till farming b)Proper irrigation  avoid salt accumulation c)Crop rotation d)Cover crops

Erosion control farming

Terracing

No erosion control