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Alluvial soil 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 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 Kaveri rivers. The 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 old alluvial (Bangar) and new alluvial (Khadar). The Bangar soil has a higher concentration of Kanker nodules than the Khadar soil. It has more fine particles and is more fertile than the Bangar.

Alluvial soil is known as