Types and Characteristics of Soils in India

Soils

Soil is the uppermost layer of the land surface, usually composed of minerals, organic matter, living organisms, air and water. Grains in the soil are of three categories namely, clay, silt, and sand. Soils are generally formed by the weathering of rocks under different conditions. Some soils are formed by the deposition of agents of denudation. Soils can vary greatly from one region to the other.

Types of Soils

The Indian Council of Agriculture Research (ICAR) set up in 1953 divides the soils of India into the following eight major groups. They are

1. Alluvial soil

2. Black soils

3. Red soils

4. Laterite soils

5. Forest and mountain soils

6. Arid and desert soils

7. Saline and alkaline soils

8. Peaty and marshy soils

Characteristics

Alluvial soil:

Khadar – light coloured, more siliceous.

Bhangar – the older alluvium composed of lime nodules and has clayey composition. It is dark in colour.

Formation - sediments deposited by streams and rivers when they slowly loose

Chemical properties - rich in potash, phosphoric acid, lime and carbon compounds but poor in nitrogen

Nature –Sandy-loam-silt-clay profile shows no marked differentiation

Black soils:

Formation - Derived from basalts of Deccan trap.

Colour - black colour, due to presence of titanium, iron.

Chemical properties - Consist of calcium and magnesium corbonates, high quantities of iron, aluminium, lime and magnesia.

Rich in potash lime, Aluminium calcium and magnesium poor in Nitrogen Phosphoric acid and humus

Nature - Sticky when wet High degree of moisture retentivity

Red soils:

Formation - decomposition of ancient crystalline rocks like granites and gneisses and from rock type

Chemical properties - rich in minerals such as iron and magnesium.

Deficient in nitrogen, humus, phosphoric acid and lime.

Nature - Light texture, porous friable presence of limited soluble salts Clay fraction of the red soils generally consists of Kaolinitic minerals.

Laterite soils:

Formation - formed in the regions where alternate wet and hot dry conditions prevail. It is formed by the process of leaching

Chemical properties - Composed mainly of hydrated oxides of iron and aluminium,

Nature - More acidic on higher areas poor in high level, cannot retain moisture while plains they consist of heavy loam and clay and easily retain moisture

Forest and mountain soils

Differ from region to region depending on climate.

Formation - due to mechanical weathering caused by snow, rain, temperature variation

Chemical properties - are deficient in potash, Phosphorus and lime.

Nature - light, sandy, thin and found with the pieces of rock. Their character changes with the parent rocks. Very rich in humus. slow decomposition makes it acidic

Arid and desert soils

Formation - Due to prevalence of the dry climate, hightemperature and accelerated evaporation, the soil is dry, it also lacks humus content due to the absence of vegetative cover

Chemical properties - Contain high percentages of soluble salts, alkaline with varying degree of calcium carbonate and are poor in organic matter; rich enough in phosphate though poor in nitrogen

Nature - light in colour, low humus,friable structure, low in moisture

Saline and alkaline soils

Formation - formed due to ill drainage which causes water logging, injurious salts are transferred from subsurface to the top soil by the capillary action, it causes the salinisation of soils

Chemical properties - liberate sodium, magnesium and calcium salts and sulphurous acid

Nature - Consists of an excess of sodium salts and mineral fragments which are weathering

Peaty and marshy soils

Formation - formed in humid regions from the organic matter. It is found in the areas of heavy rainfall and high humidity Peaty soils are black, heavyand highly acidic.

Chemical properties - deficient in potash and phosphate.

Nature - Contain considerable amount of Soluble salts and 10-40 per cent of organic matter; and high proportion of vegetable matter.