Alluvial soils are the most extensive and agriculturally significant soil group in India, formed by the deposition of sediment carried by rivers, particularly the Himalayan river systems—the Indus, Ganga, and Brahmaputra—and their tributaries. They are classified by the Indian Council of Agricultural Research (ICAR) and the National Bureau of Soil Survey and Land Use Planning (NBSS&LUP) as Inceptisols and Entisols in the USDA Soil Taxonomy. Spread across roughly 40 percent of the country's surface and covering about 15 lakh square kilometres, they form a continuous belt through the Indo-Gangetic-Brahmaputra plains and extend into the deltas of the Mahanadi, Godavari, Krishna, and Kaveri on the eastern coast, with narrow strips along the western coast. Being transported (azonal) soils rather than residual soils, their character reflects the parent rock of the catchment rather than local climate.
Alluvial soils are subdivided by age and texture. Khadar is the newer alluvium, deposited annually by floods, lighter in colour, finer in texture, and more fertile, found in the lower floodplains. Bhangar is the older alluvium, occupying higher terraces above flood level, darker, more clayey, and often containing concretions of impure calcium carbonate known as kankar. Texturally these soils range from sandy loam to clay and are generally rich in potash and lime but deficient in nitrogen, phosphorus, and humus, which is why nitrogenous fertilisers are heavily applied in the Green Revolution belt. Coastal and deltaic alluvium tends to be finer and, in tidal zones, may be saline or alkaline. In parts of the Terai and Bhabar at the Himalayan foothills, the alluvium is coarse and porous where streams re-emerge.
The fertility of alluvial soils underpins India's most productive agriculture: wheat, rice, sugarcane, pulses, oilseeds, and cotton are grown intensively across Punjab, Haryana, Uttar Pradesh, Bihar, West Bengal, and Assam, sustaining the country's highest population densities. Their renewal through annual silt deposition historically maintained fertility, though embankments, dams, and changed flood regimes have reduced this in some tracts. As of 2026, soil-health concerns in this belt—micronutrient depletion (zinc, sulphur), waterlogging, salinisation in canal-irrigated areas, and falling water tables—are central to government schemes such as the Soil Health Card programme and discussions around sustainable cropping.
For the UPSC examination, alluvial soils are a recurrent theme in the Geography optional and in General Studies Paper I (Indian geography). Prelims questions commonly test the khadar–bhangar distinction, the kankar concretions of bhangar, the nutrient profile (rich in potash, poor in nitrogen and humus), and the soil's taxonomic classification as Inceptisols/Entisols. Mains and optional answers may require linking alluvial fertility to the demographic and agricultural patterns of the northern plains, the Green Revolution, and contemporary soil-degradation challenges. Candidates should be able to contrast alluvial soils with black (regur), red, and laterite soils on the axes of origin, texture, nutrient content, and crop suitability.
Example
In Punjab's Indo-Gangetic plain, ICAR field surveys through the 2010s recorded nitrogen and zinc deficiencies in intensively cropped alluvial soils, prompting the state's expanded distribution of Soil Health Cards under the central scheme launched in 2015.
Frequently asked questions
Khadar is newer alluvium deposited by annual floods in lower floodplains—finer, lighter, and more fertile. Bhangar is older alluvium on higher terraces above flood level, darker and clayey, often containing kankar (calcium carbonate concretions).