1. Chapter 15
Soil Resources

2. What is Soil? Composed of: mineral matter organic matter Modified by:
weather
water
organisms

3. What is Soil? How Soils are Formed From parent material
Formation time varies (200 – 1000 years)
Depth varies (thin film to 10 ft)

4. What is Soil?
Soil Composition

5. What is Soil?
Soil Composition
Other components:
Humus

6. What is Soil? Soil Composition Other components: Pore space (wet soil)
Pore space (dry soil)

7. What is Soil?
Soil Horizons

8. What is Soil?
Soil Organisms

9. What is Soil?
Nutrient Cycling

10. What is Soil? Nutrient Cycling Elements in organic matter in animals
Elements incorporated into organic matter in plants
Organic matter in soil
Decomposition
Minerals freed and available to plant
Plant roots absorb minerals from soil

11. Soil Properties and Major Soil Types
Soil Texture: Sand, Silt, and Clay

12. Soil Properties and Major Soil Types
Availability of nutrient minerals in clay

13. Soil Properties and Major Soil Types
Soil Properties Affected by Soil Texture

14. Soil Properties and Major Soil Types
pH scale
Soil Acidity
Pygmy Forest
Most soils (pH = 4-8) 7
Death Valley 14

15. Soil Properties and Major Soil Types
Major Soil Groups

16. Soil Properties and Major Soil Types
Major Soil Groups

17. Soil Properties and Major Soil Types
Major Soil Groups

18. Soil Problems
Soil Erosion
Caused by water, wind, and ice

19. Soil Problems
Case-in-Point: The American Dust Bowl

20. Soil Problems
Nutrient Mineral Depletion

21. Soil Problems Soil Problems in the United States
Iowa, Missouri, Texas, & Tennessee have greatest erosion
25% of agricultural lands lose more topsoil than formed

22. Soil Problems World Soil Problems
Mineral depletion in tropical rainforest soils
Degradation in the African Sahel

23. Soil Conservation and Regeneration
Conservation Tillage

24. Soil Conservation and Regeneration
Crop Rotation
ALFALFA
4th Year
OATS
3rd Year
CORN
1st Year
SOYBEANS
2nd Year

25. Soil Conservation and Regeneration
Contour Plowing, Strip Cropping, and Terracing
Terracing
Strip cropping & contour plowing

26. Soil Conservation and Regeneration
Preserving Soil Fertility
Organic fertilizers
e.g., manure, compost
+ slow release,
- nutrient content varies
Commercial inorganic fertilizers
+ known nutrient content,
- prone to leaching

27. Soil Conservation and Regeneration
Soil Reclamation
Shelterbelts