1. Soil Profiles and Soil Classification What processes result in the formation of soil horizons? What are the typical characteristics of O, E, A, B, C and K horizons? What is CEC? % base saturation? How do these vary among different soil types? What is the role of clay minerals in nutrient retention? How are soils classified? What are the characteristics of each of the following soil orders: oxisol, alfisol, spodosol, mollisol, aridisol

2. Soil Horizons: O – Organic(>50%) plus minerals (<50%) A – Eluvial; resistate minerals plus organics B – Illuvial; clays, oxides, active weaterhing K – Cemented (carbonates, silica, gypsum) C – Partially weathered parent material

3. Soil pH: Organic decay – carbonic and organic acids Mineral buffering capacity – carbonates – fast silicates – medium to slow Leaching –removal of buffer systems – wet climate soils more likely to be acidic; arid soils to be alkaline Acid – 6.0 or less Neutral – 6.0 to 7.5 Alkaline (basic) – 7.5 or greater

4. Alfisols

5. Alfisol

6. Aridisols

7. Aridisol with subsurface ‘calcrete’ (Bk) horizon

8. Inceptisols

9. Inceptisol

10. Mollisols

11. Mollisol

12. Mollisols

13. Mollisol

14. Spodosols

15. Spodosol