Leaching is removal of materials in solution or suspension downwards as water move vertically through the soil body by force of gravity. Leaching results into movements of soluble and suspended materials in water percolation.
Leaching involves two forms:
- Elluviation – which is washing out of materials in solution or suspension from the overlying parts of the soil body; and
- Illuviation – which is the accumulation of materials taken from the overlying parts of the soil body.