A UPSC aspirant is expected to have a general understanding of all aspects of life and nature and an opinion on the same. So, it’s important to have knowledge of all the happenings of the world. General Sciences and General Knowledge are one of such aspects of the exam. 

This topic, ‘Soils of India,’ falls under the Geography section of the General Sciences and General Studies I, to be specific, which is the second paper in the Civil Services Mains Examination. While a detailed understanding of it is required for the Civil Services Mains Examination, a basic understanding of the topic is required for the Civil Services Preliminary Examination as well. 

However, this article will give you a detailed understanding of Soils and their Classification in general and specific to India in view of both Civil Services Preliminary and Mains Examinations. 

What is Soil? 

Have you ever wondered about soil? As simple as it seems, you will be surprised to learn the complexity of the soil, which is closely examined mostly by Farmers who need a certain type of soil for planting crops. It is also examined by Engineers to understand the different aspects of soil and how it impacts the naturally occurring processes of nature like Oil Erosion, Sand Storms, etc. 

How is Soil Formed? 

Soil generally develops over a period of time and is a mixture of organic and inorganic matter, providing a medium for plant life. 

Organic matter comprises living organisms like dead plants and animals, decomposing and releasing nutrients back into the soil. Inorganic matter is the materials that aren’t from or made of living organisms like minerals and weathered rocks, chemically or mechanically breaking down the rocks into smaller pieces.  

Accumulation of organic matter and washing down of the same, leaving deposits in the form of clay, humus, carbonate, iron oxide, and gypsum, forming a distinct layer on the immediate surface of the Earth. 

Scientifically speaking, soil is the active, porous medium that is developed on the uppermost layer of Earth’s crust. Soil serves as a reservoir of water and nutrients and a medium of filtration, breaking down the wastes and recycling the elements of nature. Doing all of this, soil serves as one of the major substrata of life on this Earth. 

Classification of Soils 

Soils can be classified into various types based on their structure and composition. Soil can be classified into three types, namely: Sand, Silt, and Clay. But mostly, Soils occur as different combinations of these three types. 

Major Soil deposits in India 

In ancient India, before all the current-day knowledge came into existence, soil was classified into different types: Fertile (Urvara) and Usara (Sterile). 

In the modern period, different agencies like ‘Soil Survey of India’ and ‘The National Bureau of Soil Survey and the Land Use Planning’ were established to conduct extensive research on the Indian soil. As a result of research, different characteristics of the soil like texture, composition, color, etc., were learned, and the Soils are further classified into the following major types. 

• Alluvial Soil 
• Black Soil 
• Red and Yellow Soil 
• Laterite Soil 
• Arid or Desert Soil 
• Forest Soil 
• Mountain Soil 
• Marine Deposits 

Indian soils are mainly formed by the sediments brought down by the rivers. Let us learn about them in detail. 

Alluvial Soils 

These soils are the deposits of the Indus, Ganges, and Brahmaputra rivers. The entire northern plains are made of Alluvial Soil. Some parts of eastern coastal plains are also made of this type of soil. This constitutes 43% of all the soil available in India, covering over an area of 143 square km. 

As a whole, Alluvial Soil is very fertile in nature, with enough potash, lime, and phosphoric acid. These soils are ideal for growing oilseeds, sugarcane, wheat, rice, maize, paddy, and other pulses and cereals. New alluvium is called Khader, and Old alluvium is called Bhangar. Its color ranges from ash grey to light grey. The texture is Sandy or Clay. 

Black Soils 

These soils are formed by the flow of lava. Typically found in the Deccan trap region, they spread over the northwest Deccan Plateau and extend into the southeast along the valleys Godavari and Krishna.  

Black soils are rich in iron, potassium, calcium, lime, aluminum, and magnesium and deficient in phosphorous, nitrogen, and organic matter. These soils are known for their moisture-holding capacities and have the self-ploughing characteristic. During summers or dry seasons, these soils develop cracks due to their high clay contents. This makes them respond well to irrigation. They are immune to wind and erosion and are mainly suitable for cultivating cotton. These soils are black in color (Light to Deep) and clayey in texture. 

Red and Yellow Soils 

These soils develop in the areas of low rainfall, derived from igneous and crystalline rocks. Typically found in the southern and eastern parts of Deccan Plateau. 

These types of soil develop in climates that are warm, moist, or temperate in deciduous or mixed forests. These soils are suitable for growing crops like cotton, wheat, pulses, tobacco, oilseeds, potato, etc. They are mostly made of porous and lack lime, phosphate, nitrogen, manganese, humus, and potash. They get their red color from ferric oxide. They always have a yellowish layer underneath the red layer which is in a hydrated form. Texture ranges from Sandy to Clay depending on the level of hydration. 

Laterite Soils 

These soils are typical to the states of Karnataka, Kerala, Tamil Nadu, Madhya Pradesh, and also hilly areas on Assam and Odisha. In these areas, appropriate soil conservation techniques are adopted, after which these sols would be used to grow tea and coffee. 

These soils develop in areas with heavy rainfall and high temperatures as a result of leaching. They lack humus or organic matter as all the bacteria and microorganisms are killed due to high temperatures. These soils are rich in iron and aluminum and deficient in nitrogen, potash, lime. With adequate doses of manure and sand fertilizers, these soils can be suitable for cultivation. Red laterite soils can grow crops like cashew nuts, rice, ragi, sugarcane. 

Arid or Desert Soils 

These soils are typical to the desert areas, like the Thar desert of Rajasthan. These are low-density, high-pervious soils. These Soils are deposited by erosions. 

Such Soils are formed due to negligible to no rainfall. These soils are usually not suitable for cultivation at all as there are no humus or moisture-retaining characteristics. There is Kankar in the bottom layers, which makes it almost impossible for water infiltration into the soil. But with proper irrigation techniques, cultivation becomes possible in these Soils. 

These are high in salt content; by evaporating, the water can obtain common salt from them. The color of these Soils ranges from red to brown. The texture is Sandy.  

Forest Soils 

These kinds of Soils can be typically found in rainforests where there are abundant amounts of rainfall. In the snow-covered areas, due to denudation, the soil is highly acidic in nature with low hummus, hence not suitable for cultivation. But the Soils on lower parts of the valleys are fertile and suitable for cultivation. The texture of the soil is loamy and silty. 

Mountain Soils 

These soils are found in the hill slopes and valleys of the Himalayas, as high as 2500m to 3000m. They are very high in carbon and low in nitrogen. They are dark brown in color, with textures ranging from silty to loamy. 

Marine Deposits 

These soils can be found on the narrow belt on the southeast coast of India. Their texture ranges from soft clayey to highly plastic. They contain a large amount of organic matter, a low amount of humus, and acidic in nature. They are absolutely not suitable for the construction of buildings, etc. 

 

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