There are two processes important in the evolution of the soil profile – eluviation and illuviation Eluviation: The downward transport process is called eluviation. It produces a distinct soil horizon from which matter has been removed. This is the A-horizon.
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Illuviation: Reverse of eluviation, in which matter accumulate in the underlying zone.
Water flowing down through the soil from the surface tenas to remove material from the upper part 0eluviation) and re-deposit it in the lower part {illuviation) of the soil. This action leads to the development of distinct layers of horizons.
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Details of the number of soil horizons are given below are distinctive horizontal layers identified in terms of physical and chemical composition, organic content or structure or combination properties.
i. Most horizons are visibly set apart on the basis of horizons.
ii. The soil column consists of the A and B horizons of the soil profile; these are the dynamic and distinctive layers of the profile.
iii. An Organic horizon designated by the letter Aoo lies on the A-horizon.
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iv. The C-horizon by contrast, is the parent matter.