Classification of Soils

The major types of soils found in India are:

Laterite Soil: The term is derived from the word ‘Later’ which means ‘brick’. Laterite soil is found in those regions of the country which receive heavy rainfall with an alternate dry and wet period – mainly, near the coasts. This kind of soil becomes soft when wet and hardens when dry. In these climatic conditions, leaching of soil takes place, which is a process in which a fertile portion of the soil gets washed away by heavy rains. They are formed from the decomposition of rocks and contain iron oxide, which gives them red or pink colour. This type of soil is ordinarily deficient in nitrogen and is weak in lime content; it is acidic soil. It is found in several parts of the country mainly Western and Eastern Ghats, Vindhyas, Malwa plateau and Satpuras. The states where this type of soil can be found are West Bengal, Andhra Pradesh, Bihar, Meghalaya, Assam, Odisha, to name a few. Laterite soil supports crops like Rice, Ragi, Sugarcane, rubber, coconut, tea, coffee and Cashew nuts.

Mountain Soils: Mountain soils are formed due to the accumulation of organic matter which is derived from the forest growth and is generally shallow in-depth and immature. This type of soil is rich in humus but has poor lime, potash and phosphorus content. It is usually sandy and has gravels. It is mainly found in the Himalayan region, Sikkim, Arunachal Pradesh, Assam, and also in Peninsular India, and the Eastern Ghats.

Characteristics of the mountain soil

Depending on the climate of the region, mountain soil can be divided into two broad groups: (1) Loamy Podzols, and (2) High Altitude Soils. The mid-altitudinal zone in the Himalaya has Podzols. This soil is acidic with low humus and is found in Assam, Darjeeling, Kashmir, Uttaranchal and Himachal Pradesh. Maize, barley, wheat and temperate fruits are grown in this soil in the Himalayan region. Plantation of crops like tropical fruits, coffee, tea or spices in the states of south India like Kerala, Tamil Nadu and Karnataka are undertaken in this type of soil. In the drier areas or deciduous forest belt, deep soil, brown in colour and rich in humus is found. It is perfect for orchard crops.

 

Black Soil: This type of soil is made up of volcanic rocks and lava. Black soil is also known as ‘regur’ which is derived from a Telugu word ‘reguda’. Black soil is also known as Black Cotton Soil as cotton is an important crop which is grown in this type of soil. This soil is rich in calcium carbonate, potash, lime and magnesium carbonate but has poor phosphorus content. It is mostly found in areas such as Gujarat, Madhya Pradesh and Maharashtra. It is also found in states like Tamil Nadu, Andhra Pradesh and Karnataka. Black soil is excellent and clayey and can hold a lot of moisture. It becomes sticky in the rainy season and develops cracks when dry. Black soil is good for producing cotton, oilseeds, wheat, linseed, millets, and tobacco.

Red Soil: This type of soil is formed as a result of weathering of metamorphic and igneous rocks. The red colour of the soil comes from the high percentage of iron content. The soil’s texture varies from being sandy to clayey, but it is mainly loamy. It is rich in potash content but lacks phosphate, humus and nitrogen content. The red soil is found in regions such as Tamil Nadu, Madhya Pradesh, Jharkhand, Odisha, some parts of Karnataka and southeast Maharashtra.

Alluvial Soil: Alluvial soils are formed by the deposits of the sediments brought by rivers. Most of the rivers originate from the Himalayas and bring along a high amount of sediments with them. The soil is made up of particles like silt, sand and clay. It has an adequate amount of phosphoric acid, potash and lime. Alluvial soil is of two types – (i) old alluvium known as bangar, and (ii) new alluvium called khaddar. It is the most important type of soil found in the country as it covers about 40% of the total land. It is located in the northern plains beginning from Punjab to West Bengal and Assam. It is also found in deltas of different rivers such as Krishna, Godavari, Kaveri and Mahanadi in peninsular India. Alluvial soil is highly fertile and is light grey in colour. Crops mainly cultivated include wheat, rice, maize, sugarcane, pulses, and oilseed.

Desert Soil: The desert soil is found in regions with low rainfall in an arid and semi-arid climate. The sand in the desert areas is partly original and partly blown from Indus Valley. The soil content has 90-95% of sand and 5-10% of clay. The phosphate content in the soil is high, while the nitrogen content is low. Desert soil lacks humus and moisture, and the water content in this soil is fulfilled through irrigation only. This type of soil is found in arid and semi-arid areas. Desert soil is found mostly in areas of Rajasthan extending to Rann of Kutch, and also in some areas of Haryana and Punjab. Cacti and shrubs are the permanent vegetation which can be seen in the deserts as it is very well adapted to living without moisture for long periods. Also when it rains, the presence of phosphates and nitrates make desert soil fertile, and the desert blooms as dormant seeds wake up to life.

Saline and Alkaline Soil: There are many mineral-based and un-decomposed contents inside the earth. Due to weathering, they release certain minerals such as magnesium, sodium, sulphurous acid and calcium salts. Some of the released spices get carried by rivers and mix in sub-soils of the plains making the soils saline and alkaline. Sometimes, these water-soluble salts move upwards with a rise in the water table during evaporation and transpiration. This type of soil can be found in Uttar Pradesh and Punjab and also in some parts of Gujarat. In the coastal areas, soil salinisation occurs due to accumulation of salts from inundated seawater.

Peat Soil: The accumulation of a high amount of organic matters in the soil in humid regions results in the formation of peaty soils. These types of soils constitute about 10 to 40% of the organic matter and also a reasonable amount of soluble salts. Peaty soils are heavy, black and have high acidic content. They are low in phosphate and potash content. Peaty and marshy soils are found in a few districts of Kerala. On the other hand, marshy soils are found in coastal areas of some states such as Tamil Nadu, Bihar, Almora district of Uttaranchal and Sunderbans of West Bengal.