There are seven soil deposits in India. They are alluvial soil, black soil, red soil, laterite soil, arid soil, forest soil, mountainous soil, and marsh soil. These soils are formed by various geographical factors. They also have varied chemical properties. Sundarbans mangrove swamps are rich in marsh soil. The Deccan Plateau and the Chota-Nagpur Plateau are rich in red soil due to high igneous rock content from prehistoric volcanic activity.
Major soil deposits
Alluvial Soil The rivers deposit very fine particles of soil in different parts of India. This type of soil is widespread in the Northern Plains of India. Alluvial soils are rich in humus as they are deposited by three important rivers of the Himalayas, Indus River, Ganges and Brahmaputra River. They are found in the eastern coastal plains of India, particularly in the deltas of rivers Mahanadi, Godavari River, Krishna River and Kaveri. These are generally rich in Phosphoric acid, lime and potash, and is well known for its water holding capacity which makes it ideal for growing sugarcane, paddy, wheat and other cereal crops.colour of alluvial soil is light grey or ash grey due to the presence of high iron content.
Mountain soils Mountain soils are found in the valleys and hill slopes of the Himalayas at altitudes of 2500 m to 3000 m. These soils are often the vegetation cover helps in their classification. The carbon nitrogen ratio is very wide. They are silty loam to loam in texture and dark brown in colour.
Desert soils These soils are found in Thar Desert in the Indian state of Rajasthan and Gujarat. This soil is formed from arid condition with practically negligible rainfall. It contain a high percentage of soluble salts but have low moisture content and low water-retaining capacity. This type of soil is highly pervious and have a low density. It requires to increase its bearing capacity. Commonly recognised plants that grow in these soils are cactus.
Black soils
This type of soil is black in colour. These soils are also called as regur soils. In the north-western found Deccan Plateau. The soil is suitable for growing cotton, due to which it is also known as black cotton soil. It is believed that the climatic conditions along with the parent rock material are the important factors for the formation of black soil. This type of soil is typically of the Deccan trap region spread over Northwest Deccan plateau and is made from lava flows. They cover the plateaus of Maharashtra, Saurashtra, Malwa, Madhya Pradesh, Chhattisgarh and extend in South-East direction along Godavari and Krishna valleys. These soils contain essential clay minerals as montmorillonite. These soils cover an extensive area of 300,000 square kilometres. The engineering properties of such soils are as follows:
High compressibility Low bearing capacity Low shearing strength They are made up of clayey materials. These soils are renowned for their excellent water retention. They are rich in such materials as calcium carbonate, magnesium, potash and lime. During summer, and times of high heat and low moisture, this soil develops cracks. The formation of these cracks provides an excellent mechanism of self-aeration in the soil. The soil becomes very hard when dry and muddy when wet, and thus requires deep tilling to manage drainage.
Red Soils
Red soil is a type of soil that develops in the warm, temperate, moist climate under deciduous or mixed forest, having thin organic and organic-mineral layers overlying a yellowish-brown leached layer resting on an illuvium red layer. Red soils are generally derived from crystalline rock. They are usually poor growing soils, low in nutrients and humus and difficult to cultivate because of its low water holding capacity.
Laterite soils Laterite soils are formed from chemical decomposition of rocks, the name is derived from the latin root "later", meaning "brick". soils mainly contain iron oxide which gives them characteristic pink or red color. These soils are found in Central, Eastern and Southern India. These are residual soils is formed from basalt and have high specific gravity. These soils are mostly composed as calcite depositions. They are more suitable for crops like cashew nut.
Marine deposits These soils are found in a narrow belt near the south-west coast of India. These soils have low shearing strength and high compressibility. The marine clays are soft and highly plastic. They contain large amount of organic matter and are not suitable for construction of megastructures like buildings, cranes etc.
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