The granular material that forms the upper layer of the land surface on the earth is called soil. Soil is necessary for the plants to grow. Living beings cannot live without plants as the plants provide them food. Plants provide food to the living beings. Therefore, we can say that soil is a life giving source. Soil is composed of minerals, rocks, air, water and organic matter. Soil takes millions of years to form.
Do you know how soil is formed?
The soil existed in the form of rocks about millions of years ago. Since then, the natural forces like rain, heat, water, snow etc. have been interacting with the rocks to break them into smaller rock pieces. Further, the rock pieces were converted into sand by natural forces. This sand was converted into soil by carbonic acid, bacteria and other micro-organisms. The bacteria in the soil converted the bodies of dead animals and plants into soil over a period of time. After some time, organic matter or humus made the soil more fertile. The soil is divided into four layers. The topmost layer of the soil is called the A horizon or top soil. Most of the plants grow in the topsoil. The next layer of the soil is called the B horizon or the sub soil. It is rich in minerals. By ploughing the fields, the farmers mix both the soils. A third layer of the soil is called the C horizon and the last layer of soil is called the D horizon or the bed rock.