1. 14
Soil Resources

2. A continuous process that takes thousands of years
Soil
Uppermost layer of earth’s crust that supports
plants, animals and microbes
Soil Forming Factors
Parent Material (Start with)
underlying geological material (generally bedrock) which is slowly broken down
Weathering process
Time
Climate
Organisms
Topography
A continuous process that takes thousands of years
P-COTT

3. Soil Composition - “typical soil”
Mineral Particles (45%)
Weathered rock
Organic Material (5%)
Litter, animal dung, dead remains of plants & animals
Water (25%)
Air (25%)
50% of soil is pore space
Air & water fill this space (good for plants)
Humus is a mix of many organic compounds
Helps to bind nutrients, minerals ions and hold water in the soil

4. Soil Horizons Organized into distinctive layers
- Rich in organic material
- Topsoil, dark and rich in humus
- Beneath the extent of most roots
Often saturated with water
Only Animals Expect Body CountS

5. Soil Organisms

6. Soil Organisms
There are millions of microorganisms in 1 tsp of fertile agricultural soil
Scientist have identified ~170,000 species
Ecosystem services - (bacteria & worms provide this)
Humankind benefits from a multitude of resources and processes that are supplied by ecosystems.
Decaying & cycling organic material
Breaking down toxic materials
Cleansing water
Soil aeration

7. Soil Properties Soil Texture
Relative proportion of sand, silt and clay
Gravel 2mm and up (Largest)
Sand: 2mm–0.05mm
Silt: 0.05mm–0.002mm
Clay: >0.002mm (smallest)
Know the smallest to largest or visa versa

8. Soil Properties Soil texture & pH affects soil properties
Coarse textured soil (sandy)
Excellent drainage
Fine textured soil (high in clay)
Poor drainage
Low oxygen levels in soil
Due to negatively charged surface, able to hold onto important plant nutrients (K+, Ca2+, NO2-)
Soil Acidity
Affects solubility of certain plant nutrients
pH of most soils range from 4–8
Optimum soil pH is 6–7 (nutrients are most available)

9. Accelerated by poor soil management practices
Soil Problems
Soil Erosion (Caused primarily by water and wind)
Loss in soil fertility
organic material & nutrients are eroded
Fertilizers must be used to replace nutrients lost
Desertification
relatively dry land region becomes increasingly arid
Salinization
Gradual accumulation of salt in the soil
Accelerated by poor soil management practices

10. Soil Problems - Soil Erosion
The wearing away or removal of soil top soil from the land
Causes
Most often caused by wind & water
Poor agricultural processes, removal of plant communities, unsound logging processes
Effects
Reduces plant growth
Causes loss of soil fertility
Requires additional fertilizer applications,
Leads to sediment and fertilizer deposition in waterways

11. Case in Point: American Dust Bowl
Great Plains
low precipitation and subject to drought
1930–1937 severe drought
extensive removal of native prairie grasses to plant crops
Overgrazing
unusually severe wind and storm conditions.
Winds blew soil as far east as NYC and DC.
Farmers went bankrupt

12. Soil Problems - Desertification
The process of fertile land transforming into desert inappropriate agriculture
Variety of factors
Deforestation**
Drought
Climate change 
And other human activities
Desertification has played a significant role in human history, contributing to the collapse of several large empires, such as Carthage, Greece, and the Roman Empire, as well as causing displacement of local populations
The world's most noted deserts have been formed by natural processes interacting over long intervals of time

13. Soil Problems - Salinization
Gradual accumulation of salt in the soil
due to improper irrigation techniques
Often in arid and semi-arid areas
Salt concentrations get to levels toxic to plants

14. Soil Erosion, Desertification & Salinization

15. Soil Conservation Conservation Tillage Crop Rotation Contour Plowing
Residues from previous year’s crops are left in place to prevent soil erosion
Crop Rotation
Planting a series of different crops in the same field over a period of years
Contour Plowing
Plowing around hill instead of up-down

16. Soil Conservation Strip Cropping Terracing
Alternating strips of different crops along natural contours
Terracing
Creating terraces on steep slopes to prevent erosion
Terracing

17. Soil Reclamation Two steps Best way to do this is shelterbelts
Stabilize land to prevent further erosion
Restoring soil to former fertility
Best way to do this is shelterbelts
Row of trees planted to reduce wind erosion of soil

18. Preserving Soil Fertility
Organic fertilizers
Animal manure, crop residue, bone meal and compost
Nutrient available to plants only when material decomposes
Composting is a natural fertilizer (small or large scale)
Inorganic fertilizers
Manufactured from chemical compounds
Soluble
Fast acting, short lasting
Mobile- easily leach and pollute groundwater

19. Soil Conservation Policies in US
Soil Conservation Act 1935
Authorized formation of Soil Conservation Service, now called Natural Resource Conservation Service (NRCS)
Assess soil damage & develop policies to improve soil
Food Security Act (Farm Bill) 1985
Farmers with highly erodible soil had to change their farming practices
Instituted Conservation Reserve Program
Pays farmers to stop farming highly erodible land