Soil Types of India (Classification and Characteristics) – APSC Exam Notes

Soil Types of India (Classification and Characteristics) – APSC Exam Notes

Geography Notes APSC, UPSC and State Exam Notes

Geography Notes

Soil is the most important layer of the earth’s crust. It is very important and a valuable resource. Various agents of weathering and gradation have acted upon the parent rock material to produce a thin layer of soil.

Soil is the mixture of rock debris/small rock particles, organic materials, humus which develop on the earth’s surface. Major factors that determine soils’ characteristics are parent material, climate, relief, vegetation, time, and some other life-forms. Human activities also influence it to a large extent. Main constituents of the soil are mineral particles, humus, water, and air. The amount of each of these constituents depend upon the type of soil.

It consists of three layers which are called horizons, arranged in layers known as the soil profile.

  • Horizon A is the topmost zone, where organic materials have got incorporated with the mineral matter, nutrients and water, which are necessary for plants growth.
  • ‘Horizon B’ contains matter derived from below as well as from above. It has some organic matter in it.
  • ‘Horizon C’ is composed of the loose parent material. This layer is the first stage in the soil formation process and eventually forms the above two layers.

Parent rock or the bedrock is available underneath these three horizons.

Soil Classification – Urvara vs Usara

In ancient India, the soil was classified based on only two things; whether the soil is fertile or sterile.
1. Urvara – fertile soil
2. Usara – sterile soil

After India’s Independence, scientific surveys of soils have been conducted by various agencies.

  • Soil Survey of India was established in 1956, studies of soils in selected areas like in the Damodar Valley.
  • The National Bureau of Soil Survey and the Land Use Planning of the Indian Council of Agricultural Research (ICAR) did a lot of studies on Indian soils.

On the basis of genesis, colour, composition and location, the soils of India
have been classified into the following types:
1. Alluvial soil [43%]
2. Red soil [18.5%]
3. Black / regur soil [15%]
4. Laterite soil
5. Arid / desert soil
6. Saline soil
7. Peaty / marshy soil
8. Forest soil

Alluvial soil

  • Most abundant soil types in India, covers almost 40% of total area i.e. 143 sq.km.
  • Widely available in northern plains and valleys. Also found in deltas and estuaries of peninsular India.
  • Soil is Highly fertile as they content rich amount of Humus, lime and organic matters.
  • They are depositional soil – transported and deposited by rivers, streams etc.

Features:

  • Sand content decreases from west to east of the country.
  • Colour: Light Grey to Ash Grey.
  • Texture: Sandy to silty loam or clay.
  • Rich in: potash
  • Poor in: phosphorous.

Suitable for crop cultivation – wheat, rice, maize, sugarcane, pulses, oilseed

Khadar and Bhangar

In the Upper and Middle Ganga plain, two different types of alluvial soils have developed, viz. Khadar and Bhangar.

  1. Khadar is the new alluvium and is deposited by floods annually, which enriches
    the soil by depositing fine silts.
  2. Bhangar is a system of older alluvium, deposited away from the flood plains.

Both the Khadar and Bhangar soils contain calcareous concretions (Kankars). These soils are more loamy and clayey in the lower and middle Ganga plain and the Brahamaputra valley. The sand content decreases from the west to east

Red soil or Regur Soil or Black Cotton Soil

  • Red soil covers most of the Deccan Plateau including parts of Maharashtra, Madhya Pradesh, Gujarat, Andhra Pradesh and Tamil Nadu.
  • Black soil is very deep in the upper reaches of the Godavari and the Krishna, and the north western part of the Deccan Plateau.
  • This soils are generally clayey, deep and impermeable. Swell and become sticky when wet and shrink when dried. During the dry season, these soil develop wide cracks, thus, there occurs a kind of ‘self ploughing’.
  • Black soil retains the moisture for a very long time as it has characteristics of slow absorption and loss of moisture, these helps the crops to sustain even during the dry season.

Features:

  • Rich in: lime, iron, magnesia, potash and alumina
  • Deficient in: phosphorous, nitrogen and organic matter.
  • Colour: Deep black to light black.

Suitable for crop cultivation – best soil for cotton cultivation.

Red soil

  • It develops on crystalline igneous rocks in areas of low rainfall in the eastern and southern part of the Deccan Plateau. Along the piedmont zone of the Western Ghat, long stretch of area is occupied by red loamy soil.
  • The soil develops a reddish colour due to a wide diffusion of iron/Ferric oxide in crystalline and metamorphic rocks.
  • The fine-grained red and yellow soils are normally fertile, whereas coarse-grained soils found in dry upland areas are poor in fertility.
  • Deficient in: Nitrogen, phosphorous and humus.
  • Colour: Red because of Ferric oxide.
  • Suitable for crop cultivation – Wheat, cotton, pulses, tobacco, oilseeds, potato etc.

Laterite soil

  • Laterite has been derived from the Latin word ‘Later’ which means brick.
  • These soils have mainly developed in the higher areas of the Peninsular plateau. Commonly found in Karnataka, Kerala, Tamil Nadu, Madhya Pradesh and the hilly areas of Odisha and Assam.
  • The laterite soils develop in areas with high temperature and high rainfall. These are the result of intense leaching due to tropical rains. With rain, lime and silica are leached away, and soils rich in iron oxide and aluminium compound are left behind. Thus iron oxide and potash are in available in excess.
  • Humus content of the soil is removed fast by bacteria that thrives well in high temperature., thus making these soils poor in organic matter, nitrogen, phosphate and calcium.
  • Laterites are not suitable for cultivation. Laterite soils are widely cut as bricks for use in house construction. Red laterite soils in Tamil Nadu, Andhra Pradesh and Kerala are more suitable for tree crops like cashewnut.
  • Rice, Ragi, Sugarcane and Cashew nuts are cultivated mainly.

Desert / arid soil

  • Arid soils range from red to brown in colour. They are generally sandy in structure and saline in nature. In some areas, the salt content is so high that common salt is obtained by evaporating the saline water.
  • Seen under Arid and Semi-Arid conditions. And due to the dry climate, high temperature and accelerated evaporation, they lack moisture and humus. Nitrogen is insufficient and the phosphate content is normal.
  • Lower horizons of the soil are occupied by ‘kankar’ layers because of the increasing calcium content downwards.
  • Arid soils are characteristically developed in western Rajasthan.
  • Texture: Sandy
    Colour: Red to Brown.

Saline Soils

Also known as Usara soils. It contain a larger proportion of sodium, potassium and magnesium, and thus, they are infertile, and do not support any vegetative
growth. It lack in nitrogen and calcium.

They have more salts, largely because of dry climate and poor drainage. They occur in arid and semi-arid regions, and in waterlogged and swampy areas.

More widespread in western Gujarat, deltas of the eastern coast and in Sunderban areas of West Bengal. In the Rann of Kuchchh, the Southwest Monsoon brings salt particles and deposits there as a crust. Seawater intrusions in the deltas promote the occurrence of saline soils.

In the areas of intensive cultivation with excessive use of irrigation, especially in areas of green revolution, the fertile alluvial soils are turning saline.

Excessive irrigation with dry climatic conditions promotes capillary action, which results in the deposition of salt on the top layer of the soil. In such areas,
in Punjab and Haryana, farmers are advised to add gypsum to solve the problem of salinity in the soil.

Peaty / marshy soil

  • Found in the areas of heavy rainfall and high humidity.
  • Growth of vegetation is very less.
  • A large quantity of dead organic matter/humus accumulates which makes the soil rich humus and organic content and alkaline in nature.
  • It is found widely in the northern part of Bihar, southern part of Uttaranchal and the coastal areas of West Bengal, Orissa and Tamil Nadu.

Forest soil

  • Forest soils are formed in the forest areas where high rainfall is
    available. The soils vary in structure and texture depending on the mountain environment where they are formed.
  • They are loamy and silty on valley sides and coarse-grained in the upper slopes.
  • In the snow-bound areas of the Himalayas, they experience denudation, and
    are acidic with low humus content. The soils found in the lower valleys are fertile.
  • Humus content is less and thus the soil is acidic.

Source – NCERT Books – https://ncert.nic.in/ncerts/l/kegy106.pdf