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The loose material or the upper layer of the mantle rock (regolith—a layer of lose, heterogeneous material covering solid rock) consisting mainly of very small particles and humus which can support the growth of plants is known as soil. Soil mainly consists of mineral/rock particles, a certain proportion of decayed organic matter, soil water, soil air, and living organisms which exist in a complicated and dynamic relationship with each other. The naturally occurring soil is influenced by (i) parent material, (ii) relief, (iii) climate, (iv) physical, chemical and biological agents (micro-organisms) in it, (v) land use practices, and (vi) time. In general, soil is made up of four elements: (a) inorganic or mineral fraction (derived from the parent material), (b) organic matter (decayed and decomposed plants and animals), (c) air, and (d) water.