Soil is the mixture of rock debris and organic materials which develop on the earth’s surface. The major factors affecting the formation of soil are relief, parent material, climate, vegetation and other life-forms and time. Besides these, human activities also influence it to a large extent. Components of the soil are mineral particles, humus, water and air. The actual amount of each of these depends upon the type of soil. Some soils are deficient in one or more of these, while there are some others that have varied combinations.

It consists of three layers which are called horizons. ‘Horizon A’ is the topmost zone, where organic materials have got incorporated with the mineral matter, nutrients and water, which are necessary for the growth of plants. ‘Horizon B’ is a transition zone between the ‘horizon A’ and ‘horizon C’, and contains matter derived from below as well as from above. It has some organic matter in it, although the mineral matter is noticeably weathered. ‘Horizon C’ is composed of the loose parent material.

This layer is the first stage in the soil formation process and eventually forms the above two layers. This arrangement of layers is known as the soil profile. Underneath these three horizons is the rock which is also known as the parent rock or the bedrock.

Earlier, the soil was classified based on its fertility. The soil was either ‘Urvara,’ i.e. fertile or ‘Usara’ meaning non-fertile or sterile; but in modern-day, various characteristics are taken into consideration, and the soil type is classified based on its texture, colour, or moisture content, etc. In the year 1956, Soil survey of India, an institution was established by the Government of India to study soil and its characteristics