Question

Sketch the cross-section of soil and label the various layers.

Answer 1

Hint:-A straight section of soil composed of different layers from the soil surface downwards to the soil joins the underlying stone or rocks is known as the soil profile. Every layer of soil horizon has a different physical composition (like colour, texture etc.) and Chemical composition (like minerals and nutrients).

Complete Answer:-

O = Organic horizon, A = A horizon, B = B horizon, C = C horizon, D = Bedrock.
Organic horizon is also known as a surface layer and composed of loose and somewhat ruined organic matter. A-horizon is also known as Topsoil. It is dark in colour and composed of mineral matter and rich in humus and minerals. Humus provides the nutrient for the plant to grow by making the soil fertile. This layer is soft, porous and retains a large quantity of water.
B-horizon is also known as Subsoil. In this horizon, mineral content is high, but less humus. This layer is much tougher and more compact.
C-horizon is also known as substratum. It is composed of partially altered or weathered parent material means small slabs of rocks with cracks and crevices.
Bedrock is composed of the unweathered parent material. It is hard and tough to dig with the help of spade.

Note:- Out of the four horizons, A and B horizons are extremely significant for the growth of plants because this horizon consists of minerals and nutrients for plant growth. Based on the soil category horizon A can be divided further into A1, A2 and A0. The clays and materials which are washed down from the A-horizon accumulate and form B-horizon.