7. Soil: An Essential but Somewhat Neglected Natural Resource

Soil is an essential natural resource for the existence of life on Earth. The Science dealing with soil is Pedology. Soil is a complex aggregate of inorganic ± organic matter occurring at or close to the Earth’s surface. Soil is, however, defined differently for different purposes. Soil formed even in the Archean time, but was modified subsequently. The soil section starting from the surface layer to the protolith is called soil profile. Texturally, soil is referred to three end members: sand, soil, and clay. Major composition of the soil and their relative proportions are given as follows: O > Si > Al > Fe = C = Ca > K > Na > Mg > Ti > N > S. Soil essentially forms by the decomposition (with/without transport of the products) of the exposed rocks. Commonly organic matter is added to the upper horizons. The following factors play important roles in the formation of soil: climate, activity of organisms, nature of the protolith, topography, and duration of the exposure time. There are a number of systems of classification of soils, including one proposed by FAO. However, many countries prefer to use their own system(s), based on the ground reality. Soil erosion is the worst hazard in the case of soils. Erosion means removal of the upper fertile part of the soil, by natural or human interference. A grass cover is a natural protection for the soil. Despande and Sarkar (2009) estimated the different soil types of India as follows: alfisols 13.55%, inceptisols 39.74%, aridisols 4.3%, entisols, 28.1%, vertisols 8.5%, and ultisols 2.5%. Conditions of soil formation being different in different parts of the country, nature of soil in India varies widely from place to place.