- Soil is the uppermost layer of Earth’s crust.
- Soil is the medium in which plants grow and thus it supports the lives on earth.
The soils of India on the basis of their formation are divided in the following two broad catagories :
1.Residual Soil- which form at the place of their origin. Like – black soils
2.Transported Soil- which are transported from place of their formation. Like alluvial soils.
Factors that control the formation of soil :
A number of factors contribute to the soil formation and fertility.
1.Parent rocks: –
- the rock on which the soil is formed decomposes and disintegrates under the processes of weathering.
- The characteristics of rocks influence the characteristics of soils. For example on lava rocks black soils and iron oxide rich rocks red soils are formed.
2.Climate: – climate influence the rate of weathering of rocks and type of vegetation, thus these influence the characteristics of soils.
3.Slope: -the nature of relief and slope influence the accumulation of soils. Mountains have thin soil cover but the plains have thick soil cover.
4.Time: – time provides maturity to the soil.
5.Various forces of nature such as change in temperature, actions of running water, wind and glaciers, activities of decomposers etc. contribute to the formation of soil.
6.Chemical and organic changes which take place in the soil are equally important.
- Alluvial Soils :
- Alluvial soil is the most important soil type of India.
- It covers the vast valley areas of the Sutlej, Ganga and Brahmaputra and the fringes of the southern peninsula. It is thin near the fringe of the plateau.
- It covers about 40 percent of land area of the country.
- They are depositional soils, transported and deposited by rivers and streams.
- These soils are formed by the deposition of fine sediments and silt by the rivers along their banks.
- The soils vary from sandy loam to clay in texture and are rich in potash but deficient in nitrogen and organic matter.
- Generally, the colour varies from grey to reddish brown.
- These soil are formed of deposits of silt and sand brought down by the rivers flowing from the Himalayas and the Great Indian plateau.
- Being young, the soils lack profile development.
- Being extremely productive, these soils are most important from the point of view of Indian agriculture.
- In delta region, they are ideal for jute cultivation.
- Almost all crops are grown on these soils.
- The higher proportion of clay makes the soil sticky and drainage is often poor.
They can be divided into two types:
- Young Khadar soils:
- these are newer alluvium of sandy, pale brown composition,found in lower areas of valley bottom which are flooded almost every year.
- The newer alluvium is a light friable loam with a mixture of sand and silt. It is found in river valley, the floodplains and deltas.
- It is non phorous, clayey and loamy.
- Old Bhangar soils:
- these consist of older alluvium of clayey composition and aredark in colour.
- On the other hand, the older alluvium lies on the inter fluves.
- They are coarse in nature, contain kankar (lime nodules), pebbles, gravels. They are found 30 m above flood level of the rivers.
- Both are different in texture, chemical composition, drainage capacity and fertility.
Read more About Major Soil Types