GEOG 317 Lecture Notes - Sustainable Organic Integrated Livelihoods, Starch, Aeration
16 Dec 2012
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Document Summary
Organic matter- humus- complex and resistant to decay. Water retention is higher than for mineral soils. Has chemical and physical properties of great significant to soils and plants. Sources- plant residues, animals, compost and manures, sewage sludge. Has dry matter- 25%, rest is water- 60-90% Dry matter has mostly cellulose, with other protein and lignin etc elements such as mostly carbon and oxygen with hydrogen. Rates of decomp based on how complex the molecular structure is : Sugars, starch and proteins quick decomp, fats and waxes- slow decomp. Bulk of organic material undergoes an enzymatic oxidation- called respiration: essential elements such as nitrogen, phosphorous and sulfur are mineralized or immobilized, compounds relatively resistant to microbial action are formed- soil humus. Mineralization- conversion of an element from organic to inorganic form as a result of microbial decomp. Immobilization- conversion of an element from inorganic to organic form in microbial tissues, making element unavailable to plants.
