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Explain briefly about soil and classification of soil.
Soil is a natural body consisting of layers (soil horizons) that are primarily composed of minerals, mixed with at least some organic matter, which differ from their parent materials in their texture, structure, consistency, color, chemical, biological and other characteristics. It is the unconsolidated or loose covering of fine rock particles that covers the surface of the earth. Soil is the end product of the influence of the climate, relief (slope), organisms, parent materials (original minerals), and time.

Soil types are classified according to many more factors. They are classified on the basis of colour, depth, pH, productivity, texture and process of formation.

    Soil types according to depth are as follows:
1) Shallow Soil - Soil depth less than 22.5cm. Only shallow rooted crops are grown in such soil, e.g. Paddy, Nagli.
2) Medium deep soil - Soil depth is 22.5 to 45cm. Crops with medium deep roots are grown in this type of soil e.g. Sugar cane, Banana, Gram.
3) Deep soil - Soil depth is more than 45cm. Crops with long and deep roots are grown in this type a soil e.g. Mango, coconut


The main types of soil in India are as follows:
1) Red soils
2) Laterites and lateritic soil
3) Black soil
4) Alluvial soils
5) Forest & hill soils
6) Peaty and marshy soils

1)Red soils

Red soils have two broad classes:


a) Red loam with cloddy structure and allow content of concretionary materials; and
b) Red earths with loose, Permeable top soil and a high content of secondary concretions. Generally these soils are light textured with porous and friable structure and there is absence of lime Kankar and free carbonates. They have neutral to acidic reaction and are deficient in nitrogen humus, phosphoric acid and lime.

2) Laterites and Lateritic soils

These soils are red to reddish yellow in colour and low in N, P, K, lime and magnesia. These soils are formed in-situ under conditions of high rainfall with alternation dry and wet periods. On account of heavy rainfall there is an excessive leaching of soil colloids and silica hence the soils are porous.

3) Black soils

These are mostly clay soils and form deep cracks during dry season. An accumulation of lime is generally noticed of varying depths. They are popularly known as “Black cotton soils” because of their dark brown colour and suitability for growing cotton. These are also known as Indian regurs.These soils are deficient in nitrogen, phosphoric acid and organic matter but rich in calcium, potash and magnesium.
4) Alluvial soils

These soils occur along rivers and represent the soil materials that have been deposited by the rivers duing flood. Usually they are very productive soils but many are deficient in nitrogen, humus and phosphorus.
5) Forest and hill soils

These soils occur at high elevations as well as at low elevations, where the rainfall is sufficient to support trees. These soils are very shallow, steep, stony, and infertile for the production of field crops. However, they serve a very useful purpose by supplying forest product such as timber and fuel.
6) Desert soils

These are mostly sandy soils that occur in the low rainfall track. They are well supplied with soluble salts but are low in nitrogen and organic matter and have a high pH value. These are quite productive. These are often subjected to wind erosion.
7) Saline & Alkaline soils

These soils occur in areas having a little more rainfall than the areas of desert soils. They show white incrustation of salts of calcium & Magne sium and sodium on the surface. These are poor in drainage and are infertile.
8) Peaty and Marshy soils

These types of soils are found in Kerala, coastal track of Orissa, Sunderban area of W.B. When the vegetation growing in such wet places dies, it decomposes very slowly dues to excessive wetness of soils and after several hundreds of year a layer of partly decayed organic matter accumulates on the surface, giving rise to such peaty and marshy soils. These are black coloured, heavy and highly acidic soils. When properly drained and fertilized, these soils produce good crops of rice.


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