1. Weathering and Soils

3. Weathering Breakdown of Rock near the Surface Due to Surface Processes Chemical Alteration Solution & Leaching Biological Action Hydration Mechanical Impact Wedging: Frost, Plant Roots, Salt Crystal Growth, Expansion of Hydrated Minerals

4. Salt Crystallization, Utah

5. Never Safe From Weathering

6. Weathering Rates

7. Differential Weathering and Erosion

9. Surface Area and Weathering

10. Surface-Volume Effects

11. Spheroidal Weathering

12. Spheroidal Weathering and Exfoliation

13. Spheroidal Weathering

14. Joints and Spheroidal Weathering

15. Cavernous Weathering

16. What Determines Soil Type Climate Vegetation Drainage Time Parent Material – Residual - Transported – Least Important Factor for Mature Soils

17. Soil Formation Processes Leaching from Surface K, Mg, Na Ca Si Al, Fe Accumulation beneath Surface Al, Fe in Humid Climates Ca in Arid Climates

18. Soil Horizons and Profiles Soil Horizons Layers in Soil Not Deposited, but Zones of Chemical Action Soil Profile Suite of Layers at a Given Locality

19. Principal Soil Horizons O - Organic (Humus) Often Absent A – Leaching – K, Mg, Na, Clay Removed E - Bleached Zone - Present Only in Certain Soils B – Accumulation – Absent in Young Soils – Distinct in Old Soils – Al, Fe, Clay (Moist) – Si, Ca (Arid) C - Parent Material

20. Limits of Soil Formation Balance Between: Downward Lowering of Surface Downward Migration of Horizons If erosion rapid or soil evolution slow, soils may never mature beyond a certain point. Extremely ancient soils may have lost everything movable

21. Soil Classification This may be the most difficult classification problem in science because of the many factors involved. Varied Bases for Classification Parent Material Special Constituent Materials Maturity Structure Climate & Vegetation Multiple Objectives Scientific – Genesis & Evolution Agricultural – Fertility – Most Effective Use Engineering – Slope Stability – Expansion and Shrinkage – Stability of Excavations

22. "The 7th Approximation" U.S. Soil Conservation Service 12 Soil Orders

23. "The 7th Approximation" Degree of Weathering and B Horizon Development LittleSlightModerateLargeExtreme EntisolsAridisols InceptisolsAlfisols SpodosolsUltisols MollisolsOxisols Soils Defined by Special Constituent Materials AndisolsVolcanic Ash HistosolsPeat, Organic Matter Vertisols“Self-Mixing” Clay Soils GelisolsSoils on Permafrost

24. Soils of the U.S.

25. Typical Soil Profile (Spodosol)

26. Aridisol, Kuwait

27. Ultisols: Alabama Tennessee

28. Kaolinite, Georgia

29. Oxisol, California (a Paleosol)

30. No O Horizon

31. Paleosol, Scotland

32. Loess Silt-sized Derived from Glacial Outwash in U.S. Found in U.S., E. Europe, China Parent material of world’s prime agricultural soils – Available nutrients – Fine size – lots of surface area – Cohesive – good root support – Porous – retains water well – No Rocks!!!! Windblown silt is called loess

33. Loess, Wisconsin

34. Loess in the U.S. Loess is the raw material for many mollisols, the best agricultural soils

35. Loess in Europe Loess is the raw material for many mollisols, the best agricultural soils

36. Loess in China Loess is the raw material for many mollisols, the best agricultural soils

37. Impacts of Soil Loss Lessened agricultural productivity Respiratory hazards (wind erosion) Siltation of streams – Wetland loss – Destruction of fish habitat – Obstruction of navigation Eutrophication Chemical pollution

38. Controlling Soil Loss Windrows Retain vegetation cover Contour plowing Strip cropping No-till agriculture Sediment dams

39. Strip Cropping and Contour Plowing