Lecture Notes4

Silt medium particles silt 2 20 micrometers 2 20 clay

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Unformatted text preview: meters. 2-20 Clay (fine particles): <2 micrometers. Soil Texture: Proportion of Sand, Silt, & Clay Proportion Loam: Roughly equal Loam: sand, silt, & clay san Agriculturally ideal (p. 689) 20 % 80 S Si Cl ay % 20 lt Clay 50 SiC S-Clay S-C-Loam Clay Loam 50 SiCL 80 Loam Silt Loam Sandy Loam Silt 0 S LS 100 50 20 0 100 80 % Sand Soil Organic Matter: Soil Organic component (p. 689-690; 650) 650 Organic Living soil organisms: Invertebrates Bacteria & fungi Plant roots. Nonliving Organics: Decomposing dead Decomposing organic matter. organic Humus (highly Humus decomposed organic matter). matter). Gives dark colors to soil. Soil Pore Spaces (p. 689-690; p.. 652) p Soil Approximately > 50% of soil volume. Enables root penetration &Oxygen diffusion to Enables roots. roots. Air or water depending on conditions. Clay soils: Small pores hold water tightly. Sandy soils. Large pores: rapid drainage, little remains. Large Loam soils. Loam intermediate Soil Water (p. 691; p.. 652, Fig. 29-7) p Saturation: (flooding, rain). Field capacity: moisture content when excess has drained away. Permanent wilting point: soil is so dry plants cannot remove remaining water. Soil Chemical Factors Soil Cation Exchange Capacity Cation (p. 691; 653): Slight negative charge: holds + Slight ions (Ca++, Mg++, K+, NH4+, etc). ions NH Many plant nutrients are cations. High CEC = fertile soil! Clays. Organic matter. Soil pH Soil Acidity or alkalinity of soils. Affects availability of nu...
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