Soil Structure in India

Indian Council of Agricultural Research (ICAR) has divided India Soils into eight major groups:

Alluvial Soil:

• They are by far the largest and the most important soil group of India. They are composed of sediments deposited by  rivers and the waves. Their chemical composition makes them one of the most fertile in the world. Usually deficient in nitrogen and humus (thus fertilizers are needed). 
• Occupy the plains (from Punjab to Assam) and also occur in the valleys of Narmada and Tapti in M.P. & Gujarat, 
• Mahanadi in the MP and Orissa, Godawari in A.R and Cauvery in T.N. 
• Can be divided into Khadar (new) and Bhangar (older, more clayey and kankary) alluvium. 

Black Soil:

• Also called Regur and is ideal for cotton crop. These soils have been formed due to the solidification of lava spread over large areas during volcanic activity in the Deccan Plateau, thousands of years ago. 
• They are black due to compounds of iron and aluminium (also because of titaniferous magnetite). 
• Mainly found in Deccan Plateau – Maharashtra, Gujarat, M.P, Karnataka, Andhra Pradesh, Tamil Nadu. 
• Apart from cotton cultivation, these fertile soils are suitable for growing cereals, oilseeds, citrus fruits and vegetables, tobacco and sugarcane. 
• They have high moisture retention level. 
• Lack in phosphorus, nitrogen and organic matter. 

Red Soil:

• They are mainly formed due to the decomposition of ancient crystalline rocks like granites and gneisses and from rock types rich in minerals such as iron and magnesium. The term ‘red soil’ is due to the wide diffusion of iron oxides through the materials of the soil. 
• Covers almost the whole of Tamil Nadu, Karnataka, Andhra Pradesh, S.E. Maharashtra, Chhatisgarh, parts of Orissa, Jharkhand and Bundelkhand. 
• Generally deficient in nitrogen, humus and phosphorus, but rich in potash. 
• Suitable for rice, millets, tobacco and vegetables (also groundnuts and potatoes at higher elevations). 

Laterite Soil:

• Found in typical monsoon conditions – under conditions of high temperature and heavy rainfall with alternate wet and dry periods. The alterations of wet and dry season leads to the leaching away of siliceous matter and lime of the rocks and a soil rich in oxides of iron and aluminium compounds is left behind.
• Found in parts of Western Ghats, Eastern Ghats, Rajmahal hills, Maharashtra, Karnataka, Kerala, Orissa, West Bengal, Assam, Tamil Nadu, etc. 
• Poor in nitrogen and minerals. 
• Best for tea, coffee, rubber, cinchona, coconut and suitable for rice and millet cultivation if manured. 

Forest and Mountain Soils:

• Such soils are mainly found on the hill slopes covered by forests. The formation of these soils is mainly governed by the characteristic deposition of organic matter derived from forest growth. 
• In the Himalayan region, such soils are mainly found in valley basins, depressions and less steeply inclined slopes. Apart from the Himalayan region, the forest soils occur in higher hills in south and the peninsular region. 
• Very rich in humus but are deficient in Potash, phosphorous and lime and needs fertilizers. 
• Plantation of tea, coffee, spices and tropical fruits. 

Arid and Desert Soils:

• A large part of the arid and semi-arid region in Rajasthan and adjoining areas of Punjab and Haryana lying between the Indus and the Aravallis receiving less than 50 cm of annual rainfall is affected by desert conditions. 
• This area is covered by a mantle of sand which inhibits soil growth. 
• The phosphate content of these soils is as high as in normal alluvial soils. Nitrogen is originally low but its deficiency is made up to some extent by the vailability of nitrogen in the form of nitrates. Thus the presence of phosphates and nitrates make them fertile soils wherever moisture is available. 
• The changes in the cropping pattern in the Indira Gandhi Canal Command Area are a living example of the utility of the desert soils. 

Saline and Alkaline Soils:

• In the drier parts of Bihar, Up Haryana, Punjab, Rajasthan and Maharashtra, are the salt-impregnated or alkaline soils. Known by different names: Reh, kallar, USAR, etc. 
• Some of the salts are transported in solution by the rivers and canals, which percolates in the sub-soils of the plains. 
• The accumulation of salts makes the soil infertile and renders it unfit for agriculture. 

Peaty and Marshy Soils:

• Originate in the humid regions as a result of accumulation of large amounts of organic matter in the soil. They contain considerable amounts of soluble salts and 10 – 40% of organic matter.
• Peaty soils are found in Kottayam and Alappuzha districts of Kerala, where it is called Kari.
• Marshy soils, high in vegetable matter, are found in northern Bihar, coastal parts of Orissa, Tamil Nadu and West Bengal and parts of UP.