Here is a list of soils that are found in India: 1. Alluvial Soil 2. Black Soils 3. Red Soils 4. Laterites and Lateritic Soils 5. Forest and Hill Soils 6. Desert Soils 7. Saline and Alkali Soils 8. Peaty and Marshy Soils.
Soils have been originated from disintegration and decomposition of rocks. The Indian subcontinent is characterized by a great diversity of parent rocks. These parent rocks have weathered under different condition to form soils which are in different characteristics in different regions of India.
Alluvial soils are the most important soil from the agricultural point of view and these soils are particularly found in India in the Indo-Gangetic plains.
Alluvial soils are formed on parent materials transported by different agencies viz. Water, ice, gravity and wind. The main features of alluvial soils have been derived as a silt deposition laid down by the Indian river system like the Indus, the Ganges, the Brahmaputra and the rivers like Narmada, Tapti, Mahanadi, Godavari, Krishna and Cauvery. These rivers carry the products of weathering of rocks and deposit them along their path as they flow down the plain land towards the sea.
Alluvial soils have been found in major parts of Punjab, Haryana, West Bengal, Uttar Pradesh, Assam, North Bihar and small areas in other states of India. In West Bengal, the portions of Murshidabad, Bankura, the whole of Burdwan and the western half of Midnapur are composed mainly of old alluvium. Some of the deposits may be different from one another in texture, colour, profile, chemical composition and mechanical and other physical properties. Alluvial soil covers the largest area in India (appr. 700,000 km2).
Alluvial soils are characterised by extreme depth and grey and greyish brown colour, and show mottlings, poorly drained and varying texture i.e. from sandy loam to clay loam and structure i.e. loose and free draining in case of sandy soils and compact and impervious in case of clay soils. Most commonly these soils are acidic but in drier regions, they often develop into saline and alkali soils.
Geologically alluvial soils are divided in to two groups as follows:
(a) Old alluvium soil – The old alluvium soil is known as ‘bhangar’. This soil is more clayey, dark coloured and contains concentration.
(b) New alluvium soil – The new alluvium soil is known as ‘khadar’. This soil is sandy and light coloured.
The soils differ greatly in texture and consistency, ranging from sands to loams and silts to heavy clays that are ill drained and sometimes charged with injurious accumulations of sodium salts, producing a sterile, deflocculated condition called ‘usar’. The colour of these soil is generally grey, light brown or yellowish, but those occurring in the valleys of Narmada, Tapti, Godavari and Krishna in central and Peninsular India, are of black colour.
Alluvial soils are usually deficient in nitrogen and humus and occasionally in phosphorus but not in potassium and lime. A common feature is the presence of Kankar or lime nodules which may occur intermixed with soil or as an impervious hard sub-stratum at varying depth. There is no marked differentiation into various horizons and the profile is often devoid of stratification.
Alluvial soils are suitable for cultivation of wheat (Triticum sp), Cotton (Gossypium sp), Maize (Zea mays) Paddy (Oryza sativa), oil seeds, Sugarcane (Saccharum officinarum), vegetables and fruits of many kinds. In heavy rainfall areas of Bengal, Bihar, Assam and eastern Uttar Pradesh, this soils are well suited to the growing of jute (Corchorus sp).
2. Black Soils:
Black soil is a well-known group of soil and this group derives its name from the black colour of its soil and their eminent suitability to the growing of cotton (Gossypium sp). This soil is locally known as ‘regur’ and ‘Black cotton soil’.
Black soils are mainly formed by weathering of Deccan basalt trap rocks materials consisting of disintegrated basaltic or volcanic rocks either in situ or on transported parent material. The black soils are also developed at some places on granite and gneiss containing lime and feldspar.
Black soil is common in Maharashtra, Western parts of Madhya Pradesh, parts of Andhra Pradesh, parts of Gujarat, Some parts of Tamil Nadu and Southern parts of Orissa though this soil is also found in other states also.
Black soils are highly argillaceous, very fine grained and dark in colour. Black soils are highly clayey and are characterized by high swelling and shrinkage, plasticity and stickiness. These soils are neutral to alkaline in reaction. Poor in nitrogen, organic matter and available phosphorus but rich in potassium, iron, lime, aluminium and calcium and magnesium carbonate. This soil has high cation exchange capacity (CEC). The colour of this soil is due to clay humus complex and base saturation of exchange complex and also the water status of the soil.
This soils are generally rich in montmorillonite and beidellite group of clay minerals. They are very tenacious of moisture and exceedingly sticky when wet and large and deep cracks are formed on drying. Most of the black soil is fertile but some, especially in uplands, are rather poor. The soils have impeded drainage and low permeability and due to this property the soils are prone to salinity and alkalinity under irrigation unless proper drainage is ensured.
Black soils are well suited for the cultivation of cotton (Gossypium sp.), Cereals and oil seeds such as linseed (Linum usitatissimum Linn), safflower (Carthamus tinctorius Linn), vegetables of different kinds and fruits crops such as citrus can also be grown successfully.
3. Red Soils:
Red soils are also well known group of soil and this group derives its name from the red colour of its soil, which is due to the presence of ferric oxide.
Red soils are believed to be sedentary formations derived from crystalline, metamorphic rocks which consist largely of granites, gneisses and schists with subordinate rocks rich in ferromagnesian minerals and they are formed either in situ or from the decomposed rock materials washed down to lower level by rain. Eluviation and illuviation of clay, iron, aluminium and bases are the main soil forming process.
Red soil covers large parts of Karnataka, Tamil Nadu, North-east Andhra Pradesh and the tract running along the eastern parts of Madhya Pradesh to Chotta Nagpur and Odisha. They are also commonly found in the Santhal Parganas of Bihar, Birbhum, Bankura and Midnapur (East and West) district of West Bengal, Khasi, Jaintia, Garo and Naga Hills of Assam, Jhansi, Banda and Hamirpur district of Uttar Pradesh and territory east of Aravalli Hills in Rajasthan.
The red soils are generally characterized by light texture with porous and friable structure, presence of soluble salts in small quantity, not exceeding 0.05 per cent, absence of lime kankar and free carbonates and neutral too acidic in reaction. The soils are well drained with moderate permeability. The soils are poor in humus, nitrogen, phosphorus and lime and are generally red or reddish brown in colour. The soil has medium cation exchange capacity. In West Bengal, the red soils (Sometimes misrepresented as laterites) are the transported soils from the hills of Chhota Nagpur plateau.
Morphologically, the red soils can be divided into two broad subgroups as follows:
(i) Red loams- It is characterized by argillaceous soil with cloddy structure and the presence of only a little concretionary material.
(ii) Red earth- In this soil, the top soil is loose, and friable and rich in secondary concretions due to presence of sesquioxide type of minerals.
The dominant clay mineral is kaolinite with an admixture of illite.
Red soils are suitable for cultivation of wheat (Triticum sp.) Cotton (Gossypium sp.) Maize (Zea mays), Groundnut (Arachis hypogea), Pigeon pea (Cajanus cajan), Millets (e.g. Jowar-Andropogon sorghum) Bajra (Penisetum typhoideum Linn) etc. under rainfed and irrigated condition. Some portions of red soils are also under forests.
4. Laterites and Lateritic Soils:
Laterites and lateritic soils are of special type soil of India and other tropical climatic region.
Laterite is a geological term and means literally a rock. The laterites are formed under conditions of high rainfall with alternating wet and dry periods. They are formed in situ by the leaching of bases and much of silica from original rocks. Under high rainfall conditions, silica is released and leached downward and the upper horizons of soil become rich in oxides of iron and aluminium. The lateritic soils are composed essentially of a mixture of hydrated oxides of iron and aluminium.
Laterites and lateritic soils are specially well developed on the summits of hills of Ocean, Karnataka, Kerala, Madhya Pradesh, the Ghat region of Orissa, Maharashtra and Kerala, also in West Bengal, Tamil Nadu and Assam.
Laterite soils are usually shallow and gravelly at higher lands, but are very deep loam to clay soils in valleys. This soils are not sticky and plastic when wet but it is deficient in basic elements like calcium (Ca) Magnesium (Mg) Potassium (K) and Nitrogen (N) and available Phosphorus (P). This soil has excellent physical condition due to presence of hydrous oxides of iron and aluminium and kaolinite as the dominating clay minerals.
Lateritic soils are characterized by low silica and sesquioxide ratio and completely absence of alkali and alkaline earth oxides. This soils are usually pale, gritty shallow and poor in nutrients at higher land, but are fine textured, darker hue, richer in nutrients and organic matter at lower level.
All laterites soils are porous and well drained.
Paddy (Oryza sativa) is grown well in the soil of valleys. Plantation crops (e.g. Tea-Camelia thea Linn, coffee-Coffea sp., Cinchona-Cinchona sp, Rubber-Havea brasiliensis, Cashew-Annacardium occidentale Linn) grown well at higher elevation under good soil management.
5. Forest and Hill Soils:
14 per cent of total land of India is under forest. The development of this soil is governed mainly by deposition of organic matter derived from the plants grown in this soil.
Here two conditions of soil formation may be recognized as follows:
(i) Soils are formed under acid conditions with the presence of acid raw humus and low base status which is favourable for the formation of podzol.
(ii) Soil is formed under slightly acid or neutral conditions with high base status which is favourable for the formation of brown soil. This soil occurs in Himachal Pradesh, Uttarakhand, Uttar Pradesh, Assam, Arunachal Pradesh, Meghalaya, Mizoram, Nagaland, West Bengal, Tripura, Orissa, Madhya Pradesh, Kerala, Karnataka and Tamil Nadu.
The mountain soil of West Bengal is generally brown in colour. The soil is very acidic and contains soluble salts of Manganese and humus on the surface of the soil. The soil structure is granular because soils are very rich in organic matter and nitrogen.
6. Desert Soils:
Desert soils are found in large parts of Rajasthan and south Punjab lying between the Indus River and Aravalli range. This soil consists mainly of sands which have blown mainly from coastal areas. The great desert tract of Rajasthan known as ‘Thar’ of Rajputana, consists mainly of wind brown sands. Desert soils occur under arid and semiarid condition where rainfall ranges from 50 cm to less than 100 cm, the major portion being received during the monsoon and maximum soil temperature being 50°-60°C during summer season.
Desert soils are usually saline or alkaline with unfavourable physical conditions and high pH value. The sands and soils are calcareous in nature. Nitrogen occurs in the form of nitrate. The crop production may be feasible if irrigation facility is made available.
7. Saline and Alkali Soils:
Saline and alkali soils occur mainly in arid and semiarid region of Uttar Pradesh, Uttarakhand, Punjab, Haryana, Rajasthan, Gujarat, Maharashtra and West Bengal. Saline soil (Solonchok) contains more soluble salt, mainly chloride and sulphate of Sodium (Na) Calcium (Ca) and Magnesium (Mg). The lands near the sea becomes saline due to accumulation of salt water and deposition of salts which are blown by wind.
Alkali soils contain exchangeable sodium and sodium carbonates which may help to develop poor structure. Soil becomes impervious and tight which is not congenial to proper aeration, drainage and penetration of soil mass by plant root.
8. Peaty and Marshy Soils:
Peaty soils are originated in humid regions as a result of accumulation of large amounts of organic matter in the soil. Peaty soils are found scattered in Kerala, north Bihar and north Uttar Pradesh. The lands are black and heavy and highly acidic, pH sometimes being as low as 3.9.
Marshy soils are found in coastal tracts of Orissa, in the Sunderbans and other places of West Bengal, in the central portion of North Bihar, in the Almora district of Uttarakhand and Southern east coasts of Tamil Nadu.