➤ Soil is a mixture of many solid, liquid and gaseous substances. It forms the top most layer of earth’s crust.
➤ In India there is a vast variety in the soil cover due to differences in terrain and climatic conditions.
➤ The densely-populated deltaic tract of West Bengal and the coastal plain of Kerala have rich alluvial soils and support flourishing agriculture.
➤ The shallow and coarse grained soils of Telangana and the dry regions of Rajasthan do not provide a base for developed agriculture.
➤ The process of soil formation is known as Pedogenesis.
➤ The process of soil formation depends upon factors like Parent material, Relief, Climate and Natural Vegetation.
MAJOR SOIL TYPES OF INDIA
➤ All India Soil Survey Committee has divided the Indian soils into eight major groups. They are (1) Alluvial soils, (2) Black soils, (3) Red soils, (4) Laterite and Lateritic soils, (5) Forest and Mountain soils, (6) Arid and Desert soils, (7) Saline and Alkaline soils and, (8) Peaty and Marshysoils.
SOME IMPORTANT SOIL TYPES
(1) Alluvial Soils
➤ These soils are generally confined to the river basins and coastal plains.
➤ These soils contribute significantly to the development of agriculture in India.
➤ The alluvial soils are fine-grained both in the areas of new alluvium
(Khadar) as well as the old alluvium (Bangar).
➤ These soils vary from sandy loam to clay in texture.
➤ They are generally rich in potash but poor in phosphorus, nitrogen and humus.
➤ The soils of North India are the examples of alluvial soils.
➤ These soils cover about 22% parts of the total geographical area of the country.These are azonal soils.
(2) Black Soils
➤ The black soils are concentrated over the Deccan lava tract.
➤ These are also known as the ‘black cotton soils’ or ‘Regur’ soils. These soils are famous for the cultivation of cotton.
➤ The black soils are generally clayey, deep and impermeable.
➤ Chemically the black soils consist of lime, iron, magnesium and alumina.
➤ The black soil lack in phosphorus, nitrogen and organic matter.
➤ Black soil is very retentive of moisture. It swells greatly and becomes sticky when wet in rainy season.
➤ Black soils of uplands are of low fertility but they are darker, deeper and richer in the valleys.
➤ Some of the major crops grown on the black soils are cotton, wheat, jowar, linseed, virginia tobacco, castor, sunflower and millets.
➤ These soils are mainly found in Maharashtra, Western Madhya Pradesh, parts of Karnataka, Andhra Pradesh, Gujarat and Tamil Nadu.
(3) Red Soils
➤ The reddish colour of the soil is due to the presence of iron in crystalline and metamorphic rocks.
➤ The physical properties of these soils vary from region to region.
➤ Red soils are generally shallow and their pH value ranges from 6.6 to 8.0.
➤ Red soils are poorer in quality as compared to Alluvial soils.
➤ These soils are spread on almost the whole of Tamil Nadu, parts of Karnataka, south-east of Maharashtra, eastern parts of Andhra Pradesh, Madhya Pradesh, Odisha and Chhotanagpur.
➤ By and large, the red soils are poor in lime, magnesia, phosphates, nitrogen and humus, but are fairly rich in potash.
➤ In their chemical composition they are mainly siliceous and luminous, with free quartz as sand, the alkali content is fair, some parts being quite rich in potassium.
➤ On the uplands, the red soils are thin, poor and gravelly, sandy or stony and porous, but in the lower areas they are rich, deep dark and fertile.
➤ These soils are zonal.
(4) Laterite Soils
➤ The laterite soils are formed due to the alternations of wet and dry season which leads to the leaching away of the siliceous matter of the rocks.
➤ The soils in the higher areas are generally more acidic than in low lying areas.
➤ The main development of laterite soil has taken place in the higher areas of the plateau.
➤ The laterite soils are commonly found in Karnataka, Kerala, Tamil Nadu, Maharashtra and Madhya Pradesh.
➤ The laterite soils are poor in lime and magnesia and deficient in Nitrogen.
(5) Mountain or Forest soils
➤ These soils are rich in fossils but they are undecomposed so, humic acid is formed and the soils became acidic.
➤ These soils contain thin layers because of their development on mountain slopes.
➤ These soils poor in potash, phosphours and lime. They are less fertile.
➤ Plantations are done in these soils because of their being on the mountain slopes. Plantations of tea, coffee, spices and fruits are done in these soils in India.
➤ These soils are affected by the problem of erosion.
(6) Desert or Arid Soils
➤ These are infertile soils which are alkaline in nature.
➤ These are sandy soils in which iron and phosphorous are enough but there is a deficiency of nitrogen and humus.
➤ Coarse cereals such as jowar, bajra, ragi etc and oilseeds are produced in these soils.
(7) Saline and Alkaline Soils
➤ The development of these soils has happened in those areas where dry climate is found and there is lack of proper drainage.
➤ These soils are also called ‘reh’, ‘usar’ or ‘Kollar’.
➤ These soils are rich in sodium, calcium and magnesium.
➤ These soils are deficient in nitrogen and lime.
➤ In coastal areas the coconut trees are found in plenty in these soils.
(8) Peaty or Organic Soils
➤ These soils are dark, heavy and too much acidic.
➤ These soils are formed by deposition of too much organic matter in marshy areas.
➤ These soils are found mainly in Alleppey district of Kerala, Almora in Uttarakhand, the Sunderbans delta and other lower deltaic regions.
Areawise classification of Indian soils into the following order as per the USDA soil taxonomy.
1. Inceptisols 39.74% > 2. Entisols 28.08 % > 3. Alfisols 55% > 4. Vertisols 8.52% > 5. Aridisols 4.28% > 6. Ultisols 2.51% > 7. Mollisols 0.40% > 8. Others 2.92%
Soils of India: Types and Regional Distribution
|Alluvial Soil||Ganga and Brahmaputra river valleys; deltas of Godavari and Krishna; Plains of Uttar Pradesh, Uttarakhand, Punjab, Haryana, West Bengal and Bihar; Coastal strip of peninsular India||Rice, wheat, sugarcane, oilseeds, Jute, maize, vegetables & fruits.|
|Desert Soil||Rajasthan, northern Gujarat and southern Punjab||Wheat, grams, melon, bajra (with irrigation), barley, cotton, maize, pulses.|
|Black Soil||Maharashtra and Malwa plateaus, Kathiawar peninsula, Telengana and Rayalasema region of Andhra and northern part of Karnataka, some parts of Tamil Nadu.||Cotton, millets, tobacco, sugarcane (Millets include jowar, bajra and ragi), castor, sunflower.|
|Red & yellow Soil||Scattered in peninsular India, Eastern parts of Deccan plateau, southern states of Kerala, Tamil Nadu and Karnataka, and Chhota Nagpur plateau (Jharkhand), Semi-arid tract of Rajasthan.||Millets, wheat, tobacco, rice, cotton, sugarcane, pulses, groundnut, potatoes, fruits, Oilseeds.|
|Laterite Soil||Assam hills, Tamil Nadu, Madhya Pradesh, Kerala, Karnataka, and Eastern Ghat region of Orissa.||Coffee, rubber, cashewnut, tapioca|
|Mountain Soil (It includes peat, forest and hill soils)||Coniferous forest belt of Jammu and Kashmir, Himachal Pradesh, Uttarakhand and Sikkim.||Fruits, tea, coffee, wheat, maize, barley.|
|Saline Soils||Western Gujarat, deltas of Eastern Coast & in Sunderban areas of West Bengal|
|Peaty & Marshy Soils||Northern part of Bihar, Southern part of Uttaranchal & the coastal areas of West Bengal, Orissa & Tamil Nadu|