Soil is the upper most surface layer of the earth in which plants grow and on which directly or indirectly, all life depends. It is composed of rocks, minerals, organic matter, water and air. It did not take one or two days for the soil to form but millions of years. Do you know how soil is formed?

          Millions of years ago, soil existed in the form of rocks. Since then weather and other natural forces like wind, rain, snow, water, heat etc. had been interacting with the rocks to break them into smaller fragments. These forces further converted the rock-pieces into sand. Bacteria, carbonic acid and other micro-organisms converted this sand into soil. In course of time bacteria converted the bodies of dead plants and animals also into soil.

          Soil is classified according to its colour, texture, chemical properties and climate. Colours of soil range from yellow and red to black. Soils are also categorized as acidic, alkaline and neutral. Extremely acidic or alkaline soil does not support plants. 

          There are three main types of soil a) Pedalfers – associated with temperature, humid climate, contain iron and aluminium salts, b) pedocalo – associated with low rainfall regions, contain soluable substances such as calcium carbonate and other salts and c) Laterites – tropical red or yellow soils heavily leached and rich in iron and aluminium. Based upon soil classifications, modern farming and plantation are made to yield maximum returns.

          An organic matter called humus is constantly being added to the parent soil. Humus makes the soil more fertile.

          Deep, well developed soil is divided into four layers called horizons. The top layer, where most plants grow, is called the A-horizon or top soil. This layer is rich in organic material and contains some minerals. The next is called B-horizon or sub soil. It is rich in minerals, especially in clay, but with little or no organic matter. Farmers often mix the A-and B-horizons by ploughing. The third is called C-horizon and it is a layer of weathered and shattered rocks. It is called the fragmented rock. It is quite similar to parent soil. The last layer is D-horizon or bed rocks.