(a) Humus: The rotting dead matter in the soil.

(b) Soil profile: A vertical section through different layers of the soil. (c) Horizon: Layers of the soil differs in texture colour, depth and chemical composition. These layers are referred to as horizons.

(d) Loam: Loam is a soil made of sand, clay, silt and humus. .

(e) Weathering: The process of breaking down of rocks by the action of wind, water and climate.

(f) Percolation: The process of movement of water into deeper layers of soil.