Answer: The Indian Council of Agricultural Research (ICAR) has classified Indian soils into eight types on the basis of their formation, color, composition, and location:

• Alluvial soil is depositional soil formed by silt deposited by Indo-Gangetic-Brahmaputra rivers. It varies in nature from sandy loam to clay. It is generally rich in potash but poor in phosphorus. The color varies from light grey to ash grey.
• Black soil is also known as the ‘Regur Soil’ or the ‘Black Cotton Soil’. It is generally clayey, deep, and impermeable. It shows a feature of ‘self-plowing’. It is rich in lime, iron, magnesia, and alumina and also contains potash. But they lack in phosphorous, nitrogen, and organic matter.
• Red and yellow soil wherein the soil develops a reddish color due to a wide diffusion of iron in crystalline and metamorphic rocks. It looks yellow when it occurs in a hydrated form. These soils are generally poor in nitrogen, phosphorous, and humus.
• Laterite soil develops due to intense leaching in areas with high temperatures and high rainfall. These soils are poor in organic matter, nitrogen, phosphate, and calcium, while iron oxide and potash are in excess. Hence, laterites are not suitable for cultivation; however, are widely used as bricks in house construction.
• Arid soils range from red to brown in colour. They are generally sandy in structure and saline in nature. Due to the dry climate, high temperature, and accelerated evaporation, they lack moisture and humus. Nitrogen is insufficient and the phosphate content is normal. These soils are poor and contain little humus and organic matter.
• Saline soil is also known as Usara soil. It contains a larger proportion of sodium, potassium, and magnesium, and thus, is infertile, and does not support any vegetative growth. Saline soils have more salts, largely because of dry climate and poor drainage. They lack nitrogen and calcium.
• Peaty soil is found in areas of heavy rainfall and high humidity, where large quantities of dead organic matter accumulate. This gives a rich humus and organic content which may go even up to 40-50 percent. These soils are normally heavy and black in colour.
• Forest soils vary in structure and texture depending on the mountain environment where they are formed. They are loamy and silty on valley sides and coarse-grained on the upper slopes.

Spatial distribution of these soils in India:

• Alluvial soil: It covers about 40 percent of the total area of the country and is mainly widespread in the northern plains and the river valleys. Also, in the peninsular region, they are found in deltas of the east coast and in the river valleys.
• Black soil: It covers most of the Deccan Plateau which includes parts of Maharashtra, Madhya Pradesh, Gujarat, Andhra Pradesh, and some parts of Tamil Nadu.

• Red and yellow soil: Red soil is found in the eastern and southern parts of the Deccan Plateau. Yellow and red soils are also found in parts of Odisha and Chhattisgarh and in the southern parts of the middle Ganga plain.
• Laterite soil: They are found in the higher areas of the peninsular plateau such as Karnataka, Kerala, Tamil Nadu, Madhya Pradesh, and the hilly areas of Odisha and Assam.
• Arid soil: These are characteristically developed in western Rajasthan, which exhibits characteristic arid topography.
• Saline soil: These are more widespread in western Gujarat, deltas of the eastern coast, and in Sunderbans of West Bengal.
• Peaty soil: It occurs widely in the northern part of Bihar, the southern part of Uttarakhand, and the coastal areas of West Bengal, Odisha, and Tamil Nadu.
• Forest soil: It is formed in the mountain ranges of the Himalayas, Purvanchal, Sahaydri etc. where sufficient rainfall is available.