Soil is the most important renewable natural resource of India, and it is the medium in which crops grow and upon which the entire agricultural economy depends. Soil is a mixture of mineral particles, organic matter, water and air, formed by the weathering of rocks and the decomposition of organic matter. The word "soil" comes from the Latin word "solum", meaning floor or ground. India has a great diversity of soils because of its varied geological structure, climate, relief and vegetation.
The study of soils, their formation, classification, distribution and properties is called pedology. Soil formation (pedogenesis) in India is influenced by factors such as parent material, climate, relief, vegetation and time. India's soils are broadly classified into eight major types. In this chapter we study the major soil types of India, their characteristics, distribution and their importance for agriculture.
2. Factors Affecting Soil Formation
The formation of soil depends on several factors:
1. Parent material: The rock from which the soil is derived determines its texture, colour and chemical properties. For example, basalt rocks give rise to black soils.
2. Climate: Temperature and rainfall control the rate of weathering and the type of soil formed. Chemical weathering is rapid in hot, humid regions.
3. Relief: Steep slopes have thin soils because of erosion, while flat plains have deep, fertile soils.
4. Vegetation: Plants add organic matter (humus) to the soil and bind it with their roots.
5. Time: Older soils are more developed and have distinct horizons.
3. Major Soil Types of India
India's soils are classified into eight major types on the basis of the Indian Council of Agricultural Research (ICAR) system:
3.1 Alluvial Soils
The most widespread and important soils of India, covering about 40% of the total area.
Found in the river plains of the Indus, Ganga and Brahmaputra, and in the deltas of peninsular rivers.
Formed by the deposition of river-borne sediments (alluvium), they are very fertile and rich in potash, phosphoric acid and lime, but poor in nitrogen.
Divided into Khadar (newer, lighter, more fertile alluvium) and Bangar (older alluvium with calcium carbonate nodules).
These soils support a large variety of crops, including wheat, rice, sugarcane and cotton.
3.2 Black Soils (Regur Soils)
Also called regur soils or black cotton soils.
Formed from the weathering of volcanic basalt lava, mainly in the Deccan trap region.
Found in Maharashtra, western Madhya Pradesh, parts of Gujarat, Andhra Pradesh, Karnataka and Tamil Nadu.
They are clayey, dark-coloured, retain moisture well, and develop deep cracks in summer.
Very suitable for cotton cultivation; hence also called black cotton soils.
They are rich in iron, magnesium, lime and calcium, but poor in nitrogen, phosphorus and organic matter.
3.3 Red and Yellow Soils
Formed by the weathering of crystalline and metamorphic rocks (granite and gneiss).
Found in the eastern and southern parts of the Deccan plateau, Tamil Nadu, Karnataka, Odisha, Jharkhand and parts of Madhya Pradesh.
The red colour is due to the presence of iron oxide; they become yellow when hydrated.
They are generally poor in nitrogen, phosphorus and humus.
3.4 Laterite Soils
Formed in regions of high temperature and heavy rainfall with intense leaching.
Found in the Western Ghats, parts of Karnataka, Kerala, Tamil Nadu, Maharashtra and the north-eastern states.
Leaching washes away silica and soluble minerals, leaving behind iron and aluminium oxides, giving the soil its red-brown colour.
They are poor in nitrogen, phosphorus and potash but rich in iron and aluminium oxides. They support cashew, tapioca and tea with irrigation.
3.5 Arid and Desert Soils
Found in the Thar desert of Rajasthan, and parts of Gujarat, Haryana and Punjab.
Sandy, saline and alkaline, with low organic matter and poor moisture-holding capacity.
They support drought-resistant crops like bajra, and some areas have been reclaimed by irrigation (e.g., Rajasthan canal).
3.6 Saline and Alkaline Soils
Found in arid and semi-arid regions and in poorly drained lowlands, such as parts of Haryana, Uttar Pradesh, Punjab, Gujarat and Rajasthan.
High in salts like sodium, calcium and magnesium, these soils are infertile and waterlogged (called "reh" or "usar").
They are reclaimed by flushing out salts and adding gypsum.
3.7 Peaty and Marshy Soils
Found in waterlogged areas with high organic matter, such as the Kottayam and Alleppey districts of Kerala and the deltaic regions.
Black, heavy and acidic, rich in humus but poor in potash and phosphates.
3.8 Forest and Mountain Soils
Found in the mountainous and forested regions of the Himalayas and the Western Ghats.
These soils are heterogeneous, depending on the parent rock and altitude.
In the Himalayan valleys, they are fertile, but in the higher altitudes they are thin and acidic.
4. Soil Erosion and Conservation
Soil erosion is the removal of the top fertile layer of soil by natural agents like wind and water. It is accelerated by deforestation, overgrazing, shifting cultivation and improper farming practices. The main types of soil erosion are:
- Sheet erosion: Removal of a uniform layer of soil by rain water.
- Rill erosion: Formation of small channels by running water.
- Gully erosion: Deep channels or gullies formed when rills are enlarged; makes the land unfit for cultivation (badlands).
Soil conservation measures include afforestation, contour ploughing, terracing, strip cropping, shelter belts, and the construction of bunds and check dams. The National Soil and Water Conservation Programme of the Government of India promotes these measures.
Quick Revision Tables
Major Soil Types of India
Soil Type
Region
Characteristics
Crops
Alluvial
River plains
Fertile, rich in potash and lime
Wheat, rice, sugarcane
Black (regur)
Deccan trap
Clayey, retains moisture, cracks
Cotton
Red and yellow
Deccan, Tamil Nadu
Iron oxide, poor in nitrogen
Ragi, millets
Laterite
Western Ghats
Leached, rich in iron/aluminium
Cashew, tapioca
Arid and desert
Thar desert
Sandy, saline, low moisture
Bajra
Saline and alkaline
Arid lowlands
Salty, infertile
Reclaimed for crops
Peaty and marshy
Kerala, deltas
High humus, acidic
Rice
Forest and mountain
Himalayas
Heterogeneous, thin at height
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Soil Erosion Types
Type
Description
Sheet erosion
Uniform removal of topsoil layer
Rill erosion
Small channels formed by run-off
Gully erosion
Deep gullies, land becomes badlands
Mind Map
graph TD
A["SOILS OF INDIA"] --> B["Factors of Formation"]
B --> B1["Parent material"]
B --> B2["Climate"]
B --> B3["Relief"]
B --> B4["Vegetation"]
B --> B5["Time"]
A --> C["Major Soil Types"]
C --> C1["Alluvial (40% area)"]
C --> C2["Black / Regur"]
C --> C3["Red and yellow"]
C --> C4["Laterite"]
C --> C5["Arid and desert"]
C --> C6["Saline and alkaline"]
C --> C7["Peaty and marshy"]
C --> C8["Forest and mountain"]
A --> D["Soil Erosion"]
D --> D1["Sheet, rill, gully"]
A --> E["Soil Conservation"]
E --> E1["Afforestation, terracing, contour ploughing"]
Important Diagrams (SVG)
Diagram 1: Major Soil Types and Regions
Diagram 2: Soil Erosion and Conservation
Common Mistakes
Writing that black soils are formed from sedimentary rocks; they are formed from the weathering of volcanic basalt lava.
Saying that alluvial soils are poor in potash; they are rich in potash, phosphoric acid and lime but poor in nitrogen.
Confusing laterite soils with alluvial soils; laterite soils form by intense leaching in high rainfall regions.
Writing that desert soils are rich in organic matter; they are sandy, saline and poor in organic matter.
Confusing Khadar (new alluvium, fertile) with Bangar (old alluvium, with calcium carbonate nodules).
Believing that soil erosion only means gully formation; it includes sheet, rill and gully erosion.
Writing that red soils get their colour from aluminium; the red colour is due to iron oxide.
Thinking that all Himalayan soils are fertile; mountain soils are heterogeneous and thin at high altitudes.
Exam Tips
Memorise the eight major soil types of India with their regions and main crops.
Learn that alluvial soils cover about 40% of India and are the most widespread.
For black soils, remember the key words: regur, basalt, Deccan trap, cotton, cracks in summer.
Contrast Khadar and Bangar in a two-column comparison.
Explain the factors of soil formation (parent material, climate, relief, vegetation, time).
Define the three types of soil erosion (sheet, rill, gully) and at least four conservation measures.
Note that saline-alkaline soils are called "usar" in northern India and can be reclaimed with gypsum.
Conclusion
Soils are the foundation of India's agriculture and a vital renewable natural resource. India's eight major soil types reflect its diverse geology, climate and relief: the widespread and fertile alluvial soils of the northern plains, the moisture-retaining black soils of the Deccan, the iron-rich red and leached laterite soils of the south, the sandy desert soils of the Thar, and the saline, peaty and mountain soils in their respective regions. Soil erosion by water and wind threatens this resource, but conservation measures such as afforestation, contour ploughing, terracing and the construction of bunds can protect it. The wise management of soil resources is essential for food security and the sustainable development of India.