Soils of India (Geography Project)

èIntroduction

Soil is the mixture of minerals, organic matter, gases, liquids and a myriad of organisms that can support plant life. It is a natural body that exists as part of the pedosphere and it performs four important functions: it is a medium for plant growth; it is a means of water storage, supply and purification; it is a modifier of the atmosphere; and it is a habitat for organisms that take part in decomposition and creation of a habitat for other organisms .Soil is considered the "skin of the earth" with interfaces between the lithosphere, hydrosphere, atmosphere, and biosphere. Soil consists of a solid phase (minerals and organic matter) as well as a porous phase that holds gases and water. Accordingly, soils are often treated as a three-state system .Soil is the end product of the influence of the climate, relief (elevation, orientation, and slope of terrain), biotic activities (organisms), and parent materials (original minerals) interacting over time. Soil continually undergoes development by way of numerous physical, chemical and biological processes, which include weathering with associated erosion. Most soils have a density between 1 and 2 g/cm3.Little of the soil of planet Earth is older than the Pleistocene and none is older than the Cenozoic,] although fossilized soils are preserved from as far back as the Archean.

èSoil Classification

Residual soil: A soil formed by the weathering of the bedrock immediately beneath it.

A residual soil is formed 'in place'. It is made up of rock particles weathered from the bedrock below and it is therefore chemically similar to that bedrock. It will also contain organic material derived from plants and animals living in the area.

Transported soil: A soil that has been transported (eroded) and then deposited in a region where it was not originally formed. Transported soils are the result of erosion and deposition by wind, water, and ice. Transported soils may have properties very different from the bedrock beneath them since they are unrelated. Most soils are transported. This is because the forces of erosion and deposition are constantly at work.

èTypes of Soil in India

The committee appointed by the Indian Council of Agricultural Research (ICAR), classified the Indian soil in the following main groups:

1. Alluvial Soils 2. Black Soils 3. Red Soils 4. Laterite Soils 5. Mountain Soils 6. Desert Soils

èAlluvial Soil

èFormation: Alluvial soil is formed by accumulated sediments transferred by the rivers and rapids, thus, it is amongst the most fertile soils. It is a fine-grained fertile soil deposited in river beds or by water flowing over flood plains. .Alluvial soil is composed of alluvium deposits by the rivers, when they slowly lose their carrying capacity due to decrease in velocity. While slowing down, a river loses its potential to hold the large soil particles in a suspended state and these particles thus settle down on the riverbed.

èDistribution

Alluvial soils are scattered throughout the country and is the most widespread category. These soils cover 40% of the entire land area in India. This soil covers an area of 15 lakh sq km in India and mainly contributes in the development of agriculture. They form around the lower courses of most rivers around the country and particularly all over the Indo Gangetic Plain. The entire Northern plains consists of Alluvial soil. These soils are also extended into the plains of Gujarat and are also found in the eastern coastal plains as well.

èCharacteristics

Apart from the size of their grains or particles, alluvial soils are distinguished according to their age also. They are grouped  in old alluvium and new alluvium types. The so called new alluvium may be even ten thousand years old. Locally, the old alluvium is called `Bhangar`, and the new alluvium is called `Khadar`. The old alluvium often contains Kankar nodules, with calcium carbonates in sub-soil. The new alluvium is richer compared to the old. Alluvial soils all together are exceptionally prolific. In general, they carry ample potash, lime and phosphoric acid. However, they are lacking in nitrogenous and organic substance. Alluvial soils in the drier areas of India are more alkaline in nature. Alluvial soils sustain over half the Indian population.

èCrops

From TB

èBlack Soil

Regur Soil is basically black in colour and is also known as ‘black soils’. These soils are considered perfect for

cultivation of cotton.     èFormation (From TB)

èDistribution

These soils are most characteristic of the Deccan trap (Basalt) region, spread over the north-west

Deccan plateau and are made up of lava flows. They cover the plateaus of Maharashtra, Saurashtra, Malwa and southern Madhya Pradesh and continue eastwards in the south, along the Godavari River and Krishna River Valleys.

èCharacteristics

Black soils are exceptionally delicate. Owing to the high proportion of clay, Regur soils are sticky when wet and consequently becomes difficult to plough. They are well-known for their ability to retain moisture. In addition, they are prosperous in soil nutrients, like calcium carbonate, magnesium carbonate, potash and lime. They are usually poor in phosphoric content. They develop thick fissures in the field during hot  weather . This helps in their ventilation; hence their self ploughing eminence.    èCrops (From TB)

èRed Soil

èFormation

Red Soil in India comprises of more drainage properties than other types of soils as it is formed of clay, created by wearing and tearing of limestone and formed by the breakdown of igneous rocks and metamorphic rocks. When limestone erodes, the clay enclosed within the rocks remains intact with other forms of non-soluble materials. In oxidizing conditions, rust or iron oxide develops in the clay, when the soil is present above the water table giving the soil a characteristic red colour.  èDistribution (From TB)

èCharacteristics

Red soils are formed as a result of the draining down of old crystalline rock, less clayey and sandier in nature. This is having a rich content of iron plus small humus content. The content of essential nutrients like nitrogen, phosphorus and lime is very less in red soils. Slightly acidic, it is incapable of retain moisture. It is due to the presence of iron oxide deposits, that red soils get the unique red tint and are comparatively infertile because of lime deficiency and soluble salt content. Red soils are not able to preserve moisture and hence, crops are cultivated mostly during the rainy season. In order to get higher yield in this type of soil, constant application of manures is very vital. èCrops(From TB)

èLaterite Soil

èFormation èDistributionèCharacteristics èCrops(From TB)

èSoil Erosion

Soil erosion is the washing or blowing away (by wind or water) of the top layer of soil (dirt).

This is a serious problem for people who want to grow crops. Crops are the foods that farmers grow. If the soil has eroded, the crops will not grow very well. Soil erosion was a big problem in the Midwestern United States in the 1930s dust bowl. Erosion also leaves large holes in the earth, which can weaken buildings and even cause them to collapse.

èConservation of soil

Soil erosion can be conserved in several ways.