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Soils of India: Soil science is known as pedology. The creation of soils as a result of numerous processes is referred to as pedogenesis. Relief, parent material, climate, vegetation, and other elements are among them. Furthermore, anthropogenic forces (human activities) play a role in soil formation. It is a living being that is constantly undergoing physical, chemical, and biological changes.

A UPSC applicant is required to have a broad comprehension of life and nature, as well as an opinion on the subject. As a result, it is critical to be aware of all international events. One of these aspects of the exam is General Sciences and General Knowledge.

This topic, ‘Soils of India,’ is part of the geography portion of General Sciences and General Studies I, the second exam of the Civil Services Mains Examination. While a thorough comprehension is necessary for the Civil Services Mains Exam, a basic grasp is also required for the Civil Services Preliminary Exam.

What is Soil? 

• Soil, in scientific terms, is the active, porous material that develops atop the topmost layer of the Earth’s crust. Soil acts as a storehouse for water and nutrients as well as a filtration media, breaking down trash and recycling natural components. Soil, as a result of all of this, is one of the primary substrata of life on Earth.
• As easy as it appears, you will be shocked to realise the intricacy of soil, which is thoroughly investigated primarily by Farmers who require a specific type of soil for crop growing.
• Engineers also investigate the many characteristics of soil and how they affect naturally occurring natural processes such as oil evaporation, sand storms, and so on.

Soils of India: How is Soil Formed? 

• Soil is a mixture of organic and inorganic substances that accumulates through time and serves as a medium for plant growth.
• Organic matter is made up of living creatures such as dead plants and animals that decompose and release nutrients back into the soil.
• Inorganic matter refers to things that are not derived from or formed by living beings, such as minerals and weathered rocks, which have been chemically or physically broken down into smaller bits.
• Organic matter accumulation and washing down, leaving deposits in the form of clay, humus, carbonate, iron oxide, and gypsum, producing a separate layer on the Earth’s near surface.

Soil profile or soil horizon

• Soil horizons are the vertical cross-sections of the soil. Soil horizons are the many horizontal strata found in a soil profile.
• These horizons have distinct physical and chemical properties. The many types of soil horizons are as follows.
• Organic horizon (O horizon): It is generated by the buildup of organic materials obtained from plants and animals. Surface litters, fallen leaves, and partially decomposed organic materials are also present.
• Topsoil (A horizon): It is the soil profile’s topmost mineral horizon. It is high in humus and inorganic minerals. A horizon is often referred to as the topsoil of a soil profile.
• E Horizon: It mostly consists of sand or coarse silt grains left behind by water seepage.
• Subsoil (B horizon): It is high in clay and iron and aluminum oxides. The aforementioned minerals are absorbed by the subsoil from the A and E horizons.
• Parent material (C horizon): It is made up of weathered parent mineral stuff from the soil. Saprolite is another name for the C horizon.
• Bedrock (R horizon): R horizon is made up of cemented granite, basalt, and limestone rocks.

Factors Controlling the Soil Formation

Parent material

The parent material primarily feeds the soil with bases and nutrients. The parent material determines the soil’s colour, mineral makeup, and texture. Calcareous rocks, for example, give rise to base-rich soils due to calcification.

Climate

It is a major determining element in the forms of soil formation in India. Temperature, for example, has an effect on the rate of chemical and biological processes. Precipitation, on the other hand, determines the quantity of moisture and the rate of mineral leaching in soil types.

Biotic factors

It constitutes both the flora and fauna of a region. For example, vegetation checks soil erosion by binding the soil into its roots.

Topography

The depth of soil formation is determined by topography. The soil on steep slopes, for example, is thinner than on mild slopes.

Time

 It is also one of the most important aspects in soil formation since time determines the cycle of soil recycling and rock weathering. For example, it takes hundreds of years for a thin layer of soil to develop as a result of rock fracturing. Based on their structure and chemistry, soils may be categorised into several categories. Soil may be divided into three types: sand, silt, and clay. However, most soils are a blend of these three categories.

Major Soil deposits in India 

Before all of today’s knowledge existed, ancient India had a system for classifying soil into two categories: fertile (Urvara) and usara (Sterile).

Various institutions, such as the ‘Soil Survey of India’ and the ‘National Bureau of Soil Survey and Land Use Planning,’ were founded in the contemporary era to perform significant study on Indian soil. As a result of the investigation, several soil characteristics such as texture, composition, colour, and so on were discovered, and the soils were further divided into the following primary kinds.

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

Composition of soil

• Soil is made up of both organic and inorganic materials. Weathering of rocks, for example, is an inorganic component of soil that imparts volume and weight to the soil.
• The organic component of the soil, on the other hand, is made up of dead plants and animals, plant roots, fungus, bacteria, insects, and so on.
• The liquid element of soil is known as soil solution, and it is a complicated solution required for plant growth.
• The open areas (pores) in the soil hold gases from the environment. As a result, the soil is made up of components that exist in all three phases. However, the amount of each soil component varies depending on the kind of soil.

Alluvial Soils: Soils of India

• These soils are the Indus, Ganges, and Brahmaputra rivers’ deposits. Alluvial soil covers the whole northern plains. This type of soil can also be found in portions of the eastern coastal plains.
• This accounts for 43 percent of the soil accessible in India, spanning an area of 143 square kilometres.
• Alluvial Soil is naturally exceedingly fertile, having plenty of potash, lime, and phosphoric acid. Oilseeds, sugarcane, wheat, rice, maize, paddy, and other pulses and grains thrive on these soils.
• Khader refers to new alluvium, while Bhangar refers to old alluvium. It ranges in colour from ash grey to light grey. Sandy or Clay is the texture.
• The majority of usable soil in India (approximately 43 percent) occupies an area of 143 square kilometers. It is common in the northern plains and river basins.
• They are typically found in deltas and estuaries in peninsular India. The new alluvium is known as Khadaran, and the old alluvium is known as Bhangar.

Black Soils

• The flow of lava creates these soils. They are most often found in the Deccan trap region, where they stretch throughout the northwest Deccan Plateau and continue into the southeast along the Godavari and Krishna basins.
• Iron, potassium, calcium, lime, aluminium, and magnesium are abundant in black soils, while phosphorous, nitrogen, and organic matter are low. These soils are noted for their moisture-holding capacity and self-ploughing ability.
• Because of their high clay concentration, these soils break during the summer or dry seasons. As a result, they react well to watering.
• They are resistant to wind and erosion and are mostly used for cotton cultivation. These soils range in colour from light to deep black and have a clayey texture.

Red and Yellow Soils: Soils of India

· These soils form in low-rainfall locations and are formed from igneous and crystalline rocks. Typically found in the Deccan Plateau’s southern and eastern regions.

· These soil types grow in deciduous or mixed woods in warm, damp, or temperate regions. Cotton, wheat, legumes, tobacco, oilseeds, potatoes, and other crops thrive on these soils.

· They are mostly porous and deficient in lime, phosphate, nitrogen, manganese, humus, and potash. Ferric oxide gives them their red hue.

They always have a yellowish layer underneath the red layer that is moist. Depending on the quantity of moisture, the texture ranges from sandy to clay.

Laterite Soils: Soils of India

• These soils are found in Karnataka, Kerala, Tamil Nadu, Madhya Pradesh, and hilly portions of Assam and Odisha. In these places, suitable soil conservation practices are implemented, and the soils are then utilized to cultivate tea and coffee.
• As a result of leaching, these soils form in locations with significant rainfall and high temperatures. They lack humus or organic substance because high temperatures destroy all bacteria and microbes.
• These soils are high in iron and aluminum but low in nitrogen, potash, and lime. These soils can be cultivable with proper amounts of manure and sand fertilizer.
• Crops such as cashew nuts, rice, ragi, and sugarcane may be grown on red laterite soils.

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