1. 9.2 SOILS Where the geoshpere and the bioshpere meet

2. 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.

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

4. 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

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

6. 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

7. Soils – Characteristic #4 Home to millions of species

8. Up to 3 billion organisms/gram

10. 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

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

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

15. 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

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

19. 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

20. 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

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

22. PedalferPedocalLaterite

23. 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

24. Erosion control farming

25. Terracing

26. No erosion control