Soil Resources

1. 14 Soil Resources

2. 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 HorizonsOrganized 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. 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 • 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 • Strip Cropping • Alternating strips of different crops along natural contours • Terracing • Creating terraces on steep slopes to prevent erosion Terracing

17. Soil Reclamation • Two steps • 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