Basic Process of Soil Genesis

Basic Process of Soil Genesis

During soil formation, the unconsolidated weathered material under goes many changes. These changes are brought about by variations in the four basic soil forming processes. Time required for a soil to develop the distinct layers (horizons). Horizons tend to develop more rapidly under warm, humid and forested conditions where there is enough water to move clay, humus and other colloids downward. Under ideal conditions recognisable soil profile may develop within 200 years and under less favourable conditions the time may extend to several thousand years. These four basic processes often referred as soil forming or pedogenic processes. They are responsible of soil genesis under all kind of environments.

Addition

                Inputs of materials to the developing soil profile from outside sources are considered additions. For example, fallen plant leaves, dust, twigs, animal dung, salts or silica dissolved in groundwater and deposited near or at the soil surface when rising water evaporates.

Losses

                Materials are lost from soil profile by leaching to groundwater, erosion of surface material or other forms of removal. Leaching causes the loss of water and dissolved substances such as salts or silica weathered from parent materials. Grazing of animals or harvest by people can remove large amounts of both organic matter and nutrient element.

Transformation

                It involves the physical or chemical modification of soil constituents i.e. some materials are broken down and other are synthesized. For example, weathering of primary minerals results in disintegration and alteration of various kinds of silicate clays. As primary minerals decompose, the decomposition products recombine to form new minerals which include additional type of silicate clays and hydroxides of iron aluminium. The decomposition of organic residues gives rise to organic acids, humus and other products.

Translocation

                It involves the movement of inorganic and organic material laterally within a horizon or vertically from one horizon up or down to another. Water, either percolating down with gravity or rising up by capillary action is the most common translocation agent. The material moved within the profile includes dispersed clay particles, dissolved salts and dissolved organic substances.
Soil organisms also play a major role in translocation of soil material e.g. incorporation of surface organic matter into A and B horizons by certain earth worms, transport of B and C horizons to the surface by termites and rodents.



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