India has varied relief features, landforms, climatic realms and vegetation types. These have contributed in the development of various types of soils.
- This is the most widely spread and important soil. In fact, the entire northern plains are made of alluvial soil.
- These have been deposited by three important Himalayan river systems – the Indus, the Ganga and the Brahmaputra.
- These soils also extend in Rajasthan and Gujarat through a narrow corridor.
- Alluvial soil is also found in the eastern coastal plains particularly in the deltas of the Mahanadi, the Godavari, the Krishna and the Kaveri rivers.
- The alluvial soil consists of various proportions of sand, silt and clay.
- As we move inlands towards the river valleys, soil particles appear some what bigger in size.
- In the upper reaches of the river valley i.e. near the place of the break of slope, the soils are coarse.
- Such soils are more common in piedmont plains such as Duars, Chos and Terai.
- Apart from the size of their grains or components, soils are also described on the basis of their age.
- According to their age alluvial soils can be classified as old alluvial (Bangar) and new alluvial (Khadar).
- The bangar soil has higher concentration of kanker nodules than the Khadar. It has more fine particles and is more fertile than the bangar.
- Alluvial soils as a whole are very fertile.
- Mostly these soils contain adequate proportion of potash, phosphoric acid and lime which are ideal for the growth of sugarcane, paddy, wheat and other cereal and pulse crops.
- Due to its high fertility, regions of alluvial soils are intensively cultivated and densely populated.
- Soils in the drier areas are more alkaline and can be productive after proper treatment and irrigation.
- These soils are black in colour and are also known as regur soils.
- Black soil is ideal for growing cotton and is also known as black cotton soil.
- It is believed that climatic condition along with the parent rock material are the important factors for the formation of black soil.
- This type of soil is typical of the Deccan trap (Basalt) region spread over northwest Deccan plateau and is made up of lava flows.
- They cover the plateaus of Maharashtra, Saurashtra, Malwa, Madhya Pradesh and Chhattisgarh and extend in the south east direction along the Godavari and the Krishna valleys.
- The black soils are made up of extremely fine i.e. clayey material.
- They are well-known for their capacity to hold moisture.
- In addition, they are rich in soil nutrients, such as calcium carbonate, magnesium, potash and lime.
- These soils are generally poor in phosphoric contents.
- They develop deep cracks during hot weather, which helps in the proper aeration of the soil.
- These soils are sticky when wet and difficult to work on unless tilled immediately after the first shower or during the pre-monsoon period.
Red and Yellow Soils
- Red soil develops on crystalline igneous rocks in areas of low rainfall in the eastern and southern parts of the Deccan plateau.
- Yellow and red soils are also found in parts of Odisha, Chhattisgarh, southern parts of the middle
- Ganga plain and along the piedmont zone of the Western Ghats.
- These soils develop a reddish colour due to diffusion of iron in crystalline and metamorphic rocks.
- It looks yellow when it occurs in a hydrated form.
- Laterite has been derived from the Latin word ‘later’ which means brick.
- The laterite soil develops under tropical and subtropical climate with alternate wet and dry season.
- This soil is the result of intense leaching due to heavy rain. Lateritic soils are mostly deep to very deep, acidic (pH <6.0), generally deficient in plant nutrients and occur mostly in southern states, Western Ghats region of Maharashtra, Odisha, some parts of West Bengal and North-east regions.
- Where these soils support deciduous and evergreen forests, it is humus rich, but under sparse vegetation and in semi-arid environment, it is generally humus poor.
- They are prone to erosion and degradation due to their position on the landscape.
- After adopting appropriate soil conservation techniques particularly in the hilly areas of Karnataka, Kerala and Tamil Nadu, this soil is very useful for growing tea and coffee.
- Red laterite soils in Tamil Nadu, Andhra Pradesh and Kerala are more suitable for crops like cashew nut.
- Arid soils range from red to brown in colour.
- They are generally sandy in texture and saline in nature.
- In some areas the salt content is very high and common salt is obtained by evaporating the water.
- Due to the dry climate, high temperature, evaporation is faster and the soil lacks humus and moisture.
- The lower horizons of the soil are occupied by Kankar because of the increasing calcium content downwards.
- The Kankar layer formations in the bottom horizons restrict the infiltration of water.
- After proper irrigation these soils become cultivable as has been in the case of western Rajasthan.
- These soils are found in the hilly and mountainous areas where sufficient rain forests are available.
- The soils texture varies according to the mountain environment where they are formed.
- They are loamy and silty in valley sides and coarse grained in the upper slopes.
- In the snow covered areas of Himalayas, these soils experience denudation and are acidic with low humus content.
- The soils found in the lower parts of the valleys particularly on the river terraces and alluvial fans are fertile.