The processes of eluviation and illuviation are the main forces in soil horizonation and give rise to the many layers of soil you see in a soil profile. The two processes combine to create a natural filtration system that changes soil at every level.
Eluviation
Eluviation is defined as the movement of dissolved or suspended substances away from the higher layers of the soil by rainwater that moves downward.It is the natural process in which rainwater moves downward through the soil, removing dissolved minerals, clay, and organic matter from the top layers.
It occurs in the A horizon and E horizon of the soil. Clay-sized particles, organic matter, iron, aluminium, etc., are washed away. There is coarse and light-colored soil left in the upper part of the soil.
Illuviation
Illuviation is defined as the accumulation of the washed material in the lower part of the soil. Water deposits substances as it slows at a certain layer.It happens mostly in the B horizon. The clay and humus are transported downward.This layer becomes dense and heavy in clay.
The role of climate
These processes depend highly on water. Water is a vital factor.
- Humid climate: Huge rainfall leads to very heavy processes of eluviation and illuviation.
- Dry climate: There is very little rainfall, and therefore, there is no significant soil horizon formation.
Readings:
Processes of Soil Formation
Factors Affecting Process of Soil Formation
What is Soil?: Definition, Composition, Types and Functions
