Types of Soil in India

Soil refers to the top layer of the continental crust which supports the growth of plants, trees and crops. This layer is formed by weathering of larger rocks into finer fragments. India has a diverse range of climatic conditions and geological history. These two factors lead to formation of different types of soil in India. Soils form the foundation of most civilizations. Therefore, it is necessary to understand and conserve soil. The first step to conservation of soil starts from classification of soils. Indian Council of Agricultural Research has classified the soils of India into eight categories as follows.

1. Alluvial Soil or Inceptisol

• Definition: Alluvial soil is very fertile soil. It is formed by deposition of fine sediments such as silt, sand and clay in low lying areas. It is good for most of the crops but needs irrigation depending upon the crop. This soil has do not have a standard profile due to its ex-situ origin. As per USDA classification, Entisol and Inceptisol are two subcategories of alluvial soil which refer to younger and developed deposits, respectively.
• Formation: In India, this type of soil is found in Indo-Gangetic-Brahmaputra plains. In geological past, the Tethys geosyncline lied between Angaraland and Gondwanaland. Slowly, the rivers from the land areas filled this sea with layers of alluvial sediments. In tertiary period, these layers folded into Himalayan mountains. The remaining unfolded landmass emerged above sea level as northern plains of India.
• Chemical Properties: Alluvial soil is rich in phosphates, potash and alkali. However, they lack nitrogen. The presence of lime and iron in alluvial soils varies according to the parent rock.
• Distribution: Alluvial soils covers about 46 percent of the total geographical area of India. This soil, primarily, covers the northern plains (Punjab, Haryana, Uttar Pradesh, Bihar, Jharkhand, West Bengal and Assam) of India.
• For detail on Alluvial soils, Click Here.

2. Black Soil or Vertisol

• Definition:  Black soil is dark colored soil found in deccan plateau of India. It is also known as Regur or Vertisols. As per United States Department of Agriculture (USDA) classification, Chernozem soil of grasslands is a subtype of black soil. Black soil is clayey in texture therefore can absorb water efficiently during wet season and develop wide cracks during dry season. The soil on the top start to fall into these cracks when winds blow and exposes fresh soil on top. This is why scientists also call it self tilling soil. Cotton and sugarcane are the most important crops of this region.
• Formation: During cretaceous period, a fissure developed in the peninsular part of India. Lava kept pouring out and solidified forming a thick layer of basalt on surface. Over time, the basalt layer started to weather due to effect of climatic elements. Black soil has been produced in-situ by weathering of basalt rocks into smaller particles in peninsular India.
• Chemical Properties: The black soil is rich in iron, lime, magnesium and potash. However, it is deficient in nitrogen and phosphorous. It’s black color is a result of high amount of iron and humus.
• Distribution: In India, the black soil is spread over most of Maharashtra, southern Madhya Pradesh, northern Karnataka, north-west Tamil Nadu, west Telangana and west Andhra Pradesh. It comprises of about 16% of total geographic area of India.

3. Red Soil 

• Definition:  A soil having red or orange color which is found in mineral rich regions of India is called red soil. Its color vary from red, orange, yellow and light brown. These soul are generally sandy and loamy. Red soil shares some of its characteristics with Alfisols.
• Formation:  The mineral rich areas of India particularly having iron are famous for red soil. The soil derive its color from oxidation or rusting of various metals found in the soil, specially iron.
• Chemical Properties: These soils are rich in iron oxide and potash however are deficient in nitrogen and phosphorous.
• Distribution: The regions of red soil stretches over south, south-eastern and eastern India containing states of West Bengal, Orissa, Andhra Pradesh, Telangana, Chhattisgarh, Madhya Pradesh, Karnataka and Tamil Nadu.

4. Laterite Soil

• Definition:  Laterite is very hard and compact layer of leached soil formed in hot and humid hilly regions. Laterite means brick. Therefore, the hardness of this type of soil is akin to bricks. The color of this soil may vary from red to yellow. It is a subtype of Ultisol.
• Formation:  Due to high precipitation and rain, the soluble minerals in the soil leach away leaving behind alumina and iron oxides. These soil hardens in the presence of high temperature on hilly regions forming laterite soil.
• Chemical Properties: These soils contain iron and alumina but lacks in soluble minerals such as calcium. They also lack essential minerals for cultivation such as nitrogen, potash and phosphorous.
• Distribution: The distribution of this soil is not continuous. This type of soil exists in hilly and plateau locations in western ghats, eastern ghats, Meghalaya and northeastern hills.

5. Forest and Mountain Soil

• Definition:  The soil which develop in the mountainous slopes under forest cover is termed as forest and mountain soil. This type of soil is immature and lacks clear profile due to steep slope, erosion and mass movement. It is few inches deep.
• Formation:  This type of soil forms due to weathering of rock materials in relatively stable area of mountain slope, especially where trees are present. The trees provides stability to slope and lets the soil build up.
• Chemical Properties: The texture of the soil is spontaneous i.e. sandy, loamy, clayey or rocky, depending on the parent rock. It is generally rich in organic content due to presence of vegetation cover but are generally deficient in essential minerals. So, if the forest is removed, it is very unlikely that the forest will grow again.
• Distribution: The areas of mountain soil stretches from Kashmir to Arunachal Pradesh in the in Himalayan regions.

6. Arid Soil or Aridisol

• Definition: The sandy, permeable and less fertile soils found in desert and dry regions is called arid soil.
• Formation:  In hot and dry regions, the diurnal or daily range of temperature is very high. Therefore, the rocks go through rapid expansion during hot day and contraction during cold night. Over time, the rocks lose adhesion and shatter into smaller particles leading to formation of sandy soil.
• Chemical Properties: The calcium is soluble in water but due to lack of rain, the these soils are rich in calcium or lime. It also contains adequate amount of phosphorous and iron but lacks humus, organic matter and nitrates.
• Distribution: The largest areas containing arid soil is Thar desert, Mysore region and cold desert of Leh and Ladakh.

7. Saline and Alkaline Soil

• Definition:  The soil containing large amount of salts is known as saline or alkaline soil.
• Formation:  Generally, the salts from the rocks dissolve in the water present in waterlogged soils. During the sunny days, the top layers dries up and the water starts to rise up due to capillary action. The rising water transports the salts upward while evaporating. Ultimately, the top soil becomes rich in salts. These soils also form where the soils interact or have interacted with sea water during geological past i.e. Rann of Kuchh.
• Chemical Properties: These soils are basic in nature and agriculturally infertile. They contain large amount of salts such as sodium chloride, magnesium chloride etc.
• Distribution: The largest area of saline soil is Rann of Kuchh in Gujarat. The areas with over-irrigation in Punjab, Haryana, Western Uttar Pradesh and Indira Gandhi canal area of Rajashthan are famous for saline soils.

8. Peaty and Swamp soil or Histosol

• Definition:  The peaty and swampy soil is a muck of organic matter, mud, clay, silt and water.
• Formation: The peaty soils are formed in the regions with poor water drainage i.e lack of porosity, permeability and water outlet. Over time, all the organic matter, clay, sand and humus builds up in the area leading to formation of standard peaty soil. Due to high water content, these soils are marshy.
• Chemical Properties: Generally, these soils have are acidic and have pH lower than 4. The organic carbon form about half of mass of peaty soil. These soils are rich in nitrates but deficient in phosphorous and calcium.
• Distribution: The humid regions of coastal India i.e. Kerala, Karnataka, Tamil Nadu and West Bengal are known for their swampy ecosystems. The Kayals (marine lakes) of Kerala, the delta of Sundarbans, Krishna, Cauvery and Godavari are important regions of peaty soil. The Terai belt of northern Indian plain also have peaty soils.

Conclusion

We can argue that the above classification of soils is very generic but simple. These types of soil in India does not completely reflect the diverse condition of soil system in each part of India. For instance, whole of Himalayas do not have mountain soils, some very high altitude areas have Gelisol which is not covered in this classification. However, it provides an understandable picture to the beginners and general public.