14 Soil Resources

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

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

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

Soil Organisms

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

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

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)

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

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

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

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

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

Soil Erosion, Desertification & Salinization

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

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

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

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

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