1. Soil http://www.youtube.com/ watch?v=qajjl3esi5E (intro sent out via kmail)

5. What is topsoil made of?

6. Topsoil  Soil is the topmost portion of the earth's crust; it supports life.  Soil is composed of minerals and organic material.  Composition is based on "parent" material (in the lower crust).

7. How Soil Forms  Residual Soil : parent material is bedrock beneath the soil  EX:  Transported Soils : soil is made from deposits left by wind, rivers and glaciers  EX:

8. Soil Formation  How long can take to make topsoil? (see next page)

9.  SOIL FORMATION  It can take 1,000 yrs to form topsoil.  A soil forms as parent material is weathered away.  Organic material (dead plants and animals) are mixed with weathered rock)

10. Soil composition  Every soil is a mixture of clay, silt, and sand  Clay : Very fine/small particle, tiny space between particles, dense  Silt : Too light, blown away (found in floodplains)  Sand : course, big spaces between particles

11. Soil composition Cont’d  Perfect soil for plants is Loam  LOAM: mixture of sand (40%), silt (40%), and little clay (20%)

12. Soil Horizons (fill in)  A Horizon:  B Horizon:  C Horizon:

13. Stalinization of soils  Build up of salts in soil—toxic for plants (can’t take up water)  Associated with excessive irrigation of water  Problem associated with poorly drained soils (CA, Colorado River Basin)  Treatment: flush soils with lots of water  Extreme cases: salt crust too thick to be flushed

14. Check In  1. Which zone contains weathered parent rock?  2. Which zone contains inorganic materials that have been washed from A horizon?  3. Which zone contains microorganisms that breakdown material into nutrients?

15. Soil Types  11 major categories  What affects soils composition ? (read)

16. Soil Composition  Parent material  Plants and animals  Topography---flow of water  Climate  Heavy rains wash away nutrients  Rainfall/high temp result in high clay

17. Soil is an ecosystem

18. BRAINSTORM: What would happen if we lost soil? How DO we loss soil?

19. Soil loss  Erosion: soil lost by water or wind  Chemical contamination  Salinization  Compacting by cattle hooves/machinery  40% of cropland is degraded

20. Stalinization of soils  Build up of salts in soil—toxic for plants (can’t take up water)  Associated with excessive water application/irriga6tion of water  Problem associated with poorly drained soils (CA, Colorado River Basin)  Treatment: flush soils with lots of water  Extreme cases: salt crust too thick to be flushed

21. Soil Horizons  A Horizon : (topsoil)humus, inorganic particles, microorganisms decompose organic compounds into nutrients  B Horizon : (subsoil) inorganics (iron, clay, calcium) that have been washed down into the B- horizon  C Horizon : slightly weathered parent material—rock fragments  Bedrock

22. Extension: Soil Scientists  Some things to think about:  What do scientists do?  What type of schooling do they have?  Do we need soil scientists?  http://www.youtube.com/watch?v=53pNG EO08ck&feature=related http://www.youtube.com/watch?v=53pNG EO08ck&feature=related

23. Why is soil an important resource?

24. Soil as a Resource  Countless living organisms and numerous species live in soil  Chemical processes by these organisms enable food to grow.  Soil provides the fertility for food to grow.  Soil is a very important part of an ecosystem

25. Questions?