Soil is formed over millions of years by weathering of rocks and minerals and also by natural agents like variation in temperature, climate, wind, glaciers and running water. The important factors that influence soil formation are Relief, Parent rock, Vegetation and other life forms and Time.
Soil is a natural, abiotic, renewable resource containing inorganic and organic matter, like humus. Soil is an essential resource that supports a majority of plant and animal life on the Earth. Based on their physical and chemical properties, age, texture, and colour, soils in India can be classified as: alluvial, black soil, red and yellow soil, laterite, arid and forest soil.
The northern plains of India are made of fertile alluvial soils, extending to Gujarat and Rajasthan, the Ganga and the Brahmaputra river systems. Alluvial soils are also found in the eastern coastal plains and deltas of the Godavari, the Mahanadi, the Krishna and the Kaveri.
Alluvial soil is a mixture of sand, silt and clay. The new alluvial soils called Khadar found in the Gangetic plains have small particles and a fine texture. The old alluvial soils called Bangar found near the river valleys are coarser and contain more pieces of rocks called Kanker. The fertile alluvial soils are rich in potash, phosphoric acid and lime and are ideal for growing sugarcane, wheat, rice, pulses and cereal crops.
Black soil (also called regur) is found in the Deccan plateau spread over Maharashtra, Saurashtra, Malwa, Madhya Pradesh and Chhattisgarh. Black soil is rich in calcium carbonate, potash, magnesium, lime and good water retention properties. It is ideally suited for the cultivation of cotton.
Red and yellow soils are found in southern and eastern parts of Deccan plateau, southern Gangetic plains, along the Western Ghats and some parts of Orissa and Chhattisgarh. The high iron content makes this type of soil good for cultivating various types of grams, groundnuts and castor seeds. Laterite soils are found in Kerala, Karnataka, Madhya Pradesh, Tamil Nadu and parts of Orissa and Assam. Laterite soil is good for cultivation of tea, coffee and cashewnuts.
Arid soil is found in western Rajasthan and parts of Kutch region in Gujarat that receive very little rainfall. Arid soil is low in moisture and organic content and has high salt content. Arid soil is being used for cultivation of bajra and wheat crops in some places of western Rajasthan where irrigation facility is available.
Forest soils are found in the mountainous regions of the Himalayas from Kashmir to Arunachal Pradesh. Wheat, rice, sugarcane, and oil seeds are cultivated in forest soils of many parts in Jammu and Kashmir and Arunachal Pradesh.