A large number of processes are responsible for the formation of soils. This fact is evident by the large number of different types of soils that have been classified by soil scientists.
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However, at the macro-scale we can suggest that there are five main principal pedogenic processes acting on soils. These processes are laterization, podzolization, calcification, salinization, and gleization.
Laterization:
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It is a pedogenic process common to soil found in tropical and subtropical environments. High temperatures and heavy precipitation result in the rapid weathering of rocks and minerals. Movements of large amounts of water through the soil cause eluviation and leaching to occur.
Almost all of the byproducts of weathering, very simple small compounds or nutrient ions, are translocated out of the soil profile by leaching if not taken up by plants for nutrition. The two exceptions to this process are iron and aluminium compounds. Iron oxides give tropical soils their unique reddish colouring. Heavy leaching also causes these soils to have an acidic pH because of the net loss of base cations.
Podzolization:
It is associated with humid cold mid-latitude climates and coniferous vegetation. Decomposition of coniferous litter and heavy summer precipitation create a soil solution that is strongly acidic. This acidic solid solution enhances the processes of eluviation and leaching causing the removal of soluble basecations and aluminium and iron compounds from the A horizon. This proctcs creates a sub-layer in the A horizon that is white to grey in colour and composed of silica sand.
Calcification:
It occurs when evaportranspiration exceeds precipitation causing the upward movement of dissolved alkaline salts from the groundwater. At the same time, the movement of rain water causes a downward movement of the salts. The net result is the deposition of the translocated cations in the B horizon. In some cases, these deposits can form a hard layer called caliche. The most common substance involved in this process is calcium carbonate. Calcification is common in the prairie grasslands.
Salinization:
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It is a process that functions in the similar to calcification. It differs from calcification in that the salt deposits occur at or vary near the soil surface. Salinization also takes place in much drier climates.
Gleization:
It is a pedogenic prccoss associated with poor drainage. This process involves the accumulations of organic matter in the upper layers of the soil. In lower horizons, mineral layers are stained blue-grey because of the chemical reduction of iron.
