Give a detailed account of soil …

Soil is composed of distinct layers. The rotting matter in the soil is called humus. A vertical section through the soil showing the different layers of soil is called soil profile. Soil profile consists of three different layers of soil. Each layer of soil is called a horizon. The three layers of soil in the soil profile are:

1. A-horizon or Top-soil: The uppermost horizon is generally dark in colour as it is rich in minerals and humus. The humus makes the soil fertile and provides nutrients to growing plants. This layer is generally soft, porous and can retain more water. The plant roots grow in the top soil. This layer contains many living things like worms, rodents, and moles etc. Bacteria and fungi also occur in top soil. This layer contains lot of dead and decaying matter which makes it the most fertile layer. It is called the topsoil or the A-horizon.
2. B-horizon or Subsoil: The layer of soil which is just below the top-soil is called B-horizon. This layer has a lesser amount of humus but more of minerals. This layer is generally harder and more compact and made up of slightly bigger rock particles than that of top-soil. The subsoil is light in color compared to upper layer.
3. C-horizon or Sub-stratum: The third layer is the C-horizon, which is made up of small lumps of rocks with cracks and crevices. Below this layer is the bedrock, which is hard and difficult to dig with a spade.

The soil profile could be seen below the top surface by looking g at the sides of a recently dug trench or can be seen at the sides of a road on the hill or a steep river bank.