EES 1080 Lecture Notes - Lecture 12: Soil Texture, Intercropping, Silt
22 Jan 2018
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Physical weathering: (wind, rain, thermal expansion, and contraction, water freezing), chemical. Weathering (water and gases), and biological weathering (tree roots and lichens); parent. Material (rock) -----> smaller particles of parent material. Near the surface there is more organic material from the grass and surface materials. Air 25%, mineral particles 45%, water 25%, and organic matter 5% (organisms 10%, roots 10%, and. O- horizon: organic (litter layer): organic matter deposited by organisms. A-horizon: topsoil: some organic material mixed with mineral components. E-horizon: eluviated (leaching layer): minerals and organic matter tend to leach out of this horizon. B: horizon: subsoil: minerals and organic matter accumulate here. C: horizon: weathered parent material: initial step in soil formation. R: horizon: rock (parent material): bedrock, lava, etc. Soil texture is partly determined by particle size: soils are usually a mixture of clay, sand, silt. Clay: smallest particle size, type of mineral, retain moisture for a long time.
