Soil is the most important renewable natural resource. Soil resources are the medium of plant growth and support different types of living organisms on the earth. The soil is a living system. It takes millions of years to form soil upto a few cm in depth. Relief, parent rock or bedrock, climate, vegetation, and other forms of life and time are important factors in the formation of soil or soil resources.

Various forces of nature such as a change in temperature, actions of running water, wind and glaciers, activities of decomposers, etc. contribute to the formation of soil. Chemical and organic changes which take place in the soil are equally important. Soil also consists of organic (humus) and inorganic materials.

On the basis of the factors responsible for soil formation, color, thickness, texture, age, chemical and physical properties, the soils of India can be classified into different types.

Classification of Soils

India has varied relief features, landforms, climatic realms, and vegetation types. These have contributed to the development of various types of soils.

Alluvial 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 KaveririversThe alluvial soil consists of various proportions of sand, silt, and clay.

As we move inland towards the river valleys, soil particles appear somewhat 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:

1. Old alluvial (Bangar)
2. New alluvial (Khadar).

The bangar soil has a 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 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.

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.

Read More: Types of Soil: Sandy Soil, Clay Soil, and Loamy Soil with Properties