Classification of Soils

 

Classification of Soils

On the basis of the factors responsible for soil formation, colour, thickness, texture, age, and chemical and physical properties, the soils of India are classified into different types, as mentioned below.

Alluvial Soils

1. The entire northern plains are made of alluvial soil.
2. The Alluvial Soil is deposited by 3 important Himalayan river systems – the Indus, the Ganga and the Brahmaputra.
3. It is also found in Rajasthan, Gujarat and eastern coastal plains, particularly in the deltas of the Mahanadi, the Godavari, the Krishna and the Kaveri rivers.
4. The alluvial soil consists of various proportions of sand, silt and clay. As we move inland towards the river valleys, soil particles appear to be bigger in size whereas in the upper side of the river valley, the soils are coarse.
5. Based on age, Alluvial soils can be classified as:
6. Old Alluvial (Bangar): The Bangar soil has a higher concentration of kanker nodules than the Khadar.
7. New Alluvial (Khadar): It has more fine particles and is more fertile than the Bangar.
8. Alluvial soils are very fertile. These soils contain an adequate proportion of potash, phosphoric acid and lime, which are ideal for the growth of sugarcane, paddy, wheat and other cereal and pulse crops.

Black Soil

1. This soil is black in colour and is also known as regur soil. Climatic conditions, along with the parent rock material are the important factors for the formation of black soil.
2. The soil is ideal for growing cotton and is also known as black cotton soil.
3. This type of soil is typical of the Deccan trap (Basalt) region spread over the northwest Deccan plateau and is made up of lava flows.
4. The soil covers the plateaus of Maharashtra, Saurashtra, Malwa, Madhya Pradesh and Chhattisgarh and extends in the southeast direction along the Godavari and the Krishna valleys.
5. The black soils are made up of extremely fine i.e. clayey material and are well-known for their capacity to hold moisture.
6. Black soil is nutrients rich and contains calcium carbonate, magnesium, potash and lime.
7. The soil is 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

1. This type of soil develops on crystalline igneous rocks in areas of low rainfall in the eastern and southern parts of the Deccan plateau.
2. These soils develop a reddish colour due to the diffusion of iron in crystalline and metamorphic rocks. It looks yellow when it occurs in a hydrated form.
3. Found in parts of Odisha, Chhattisgarh, southern parts of the middle Ganga plain and along the Piedmont zone of the Western Ghats.

Laterite Soil

1. The laterite soil develops under tropical and subtropical climates with the alternate wet and dry season.
2. This soil is the result of intense leaching due to heavy rain.
3. Lateritic soils are acidic (pH<6.0) in nature and generally deficient in plant nutrients. This type of soil is found mostly in Southern states, Western Ghats region of Maharashtra, Odisha, some parts of West Bengal and the northeast regions.
4. The soil supports deciduous and evergreen forests but humus poor.
5. This soil is very useful for growing tea and coffee.

Arid Soils

1. Arid soils range from red to brown in colour.
2. This soil is 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.
3. Arid soil lacks humus and moisture.
4. 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.

Forest Soils

1. These soils are found in the hilly and mountainous areas.
2. The soil texture is loamy and silty on the valley sides and coarse-grained on the upper slopes.
3. In the snow-covered areas of the Himalayas, these soils experience denudation and are acidic with low humus content. The soil is fertile on the river terraces and alluvial fans.

The map below shows the different types of soils found in India.