Soil is the uppermost layer of Earthâ€™s crust.
Soil is the medium in which plants grow and thus it supports the lives on earth.
How soils are formed?
Soils are formed due to the weathering of rocks.
WHAT IS SOIL?
Soil is the thin layer of loose mixture of small rock particles and rotting organic matter that covers much of the worldâ€™s land surface.
Soil formation is a very long process. It begins with the weathering of rocks into small fragments. The rocks are also worn away by the agents of erosion like river, wind, sea and glacier. The sediments and tiny rock particles are then deposited by the agents of erosion. The accumulation of such sediments over the ages forms soil. Eventually, the plants that grow on the soil, shed their leaves which decay to form the topmost layer of soil called 'humus'.
India is primarily an agricultural country. The success of agriculture depends upon the fertility of soils. The soils of India are classified into the following main groups depending upon the rock cover and climatic conditions.
The most two important factors that determine the types of soil found in India are : i. The climate ii. The topography
The soils of India on the basis of their formation are divided in the following two broad catagories.
1.Residual Soil 2.Transported Soil
The major soil groups are:
Black soils are mainly found over the Deccan lava tract (Deccan Trap) including Maharashtra, Madhya Pradesh, Gujarat and Andhra Pradesh. These soils are found in river valley of Narmada, Tapi, Godavari and Krishna. These soils have been formed due to the weathering of the lava rocks. This is also known as the Regur soil and Cotton soil. These soils are rich in lime. iron, magnesia and alumina but lack in the phosphorus, nitrogen and organic matter.
It is formed by the weathering of igneous rocks and the cooling of lava after a volcanic eruption.
In India, extensive deposits of black soil are found in the Deccan Plateau which includes parts of Maharashtra, Madhya Pradesh, Gujarat, Andhra Pradesh, parts of Tamil Nadu.
In the upper parts of Godavari and Krishna, the north western part of Deccan Plateau, black soil is very deep.
BLACK SOIL IS:-
Clayey, deep and impermeable
They swell and become sticky when wet and shrink when dried
During dry season, these soils develop wide cracks.
Rich in lime and iron, magnesia and alumina
Also contain potash
Lack phosporus, nitrogen and organic matter
Colour of the soil ranges from deep black of grey.
Known as Black Cotton Soils.
Dark in colour, suitable for cotton cultivation Are residual soils, i.e. they are formed at the place of their origin over the underlying rocks.
Are formed in situ, i.e. formed where they are found.
Therefore, they are essentially formed by weathering of Deccan Trap.
Spread over an area of 5.4 sq. km., i.e. 16.6 % of the total land area of the country.
* Fine textured and clayey in nature .
* Has high qualities of lime, iron, mangnesium, and generally poor percentage of phosphorous, nitrogen and organic matter.
* Black in colour as it is formed from weathered lava rocks
Soilâ€™s colour also varies from Black to Chestnut brown
Very clayey and therefore highly retentive of water. Because of high clay content, these soils expand when wet and become difficult to plough.
During dry season, black soils shrink and develop big cracks which help in air circulation .
Soil is very fertile in most of places.
Poor in nitrogen, phosphorous, potassium, and organic matter and rich in potash and lime.
Needs irrigation support for cultivation
Contains soluble salts in small quantities.
Cultivation is done with the help of fertilizers .
Suited for dry farming as it does not require much moisture.
Suitable for growing cereals, rice, wheat, jowar, oilseeds, citrus...