Soil is the upper layer of earth. It is one of the three major natural resources besides air and water. It is formed by weathering of rocks into very small and minute fragments. It can be of different colours such as yellow, red, black or dark brown. It is composed of a mixture of organic remains (decayed plant and animal parts), clay and rock particles. The soil which is suitable for plant growth has more of minerals and decayed organic matter and less of rock particles. Other types of soil are sandy, clayey and stony.