The Ganga basin is characterized by a wide variety of soils. The soils of the high Himalayas in the north are subject to continued erosion and the Gangetic trough provides a huge receptacle into which thousands of metres of thick sediment layers are deposited to form a wide valley plain. The plateau on the south has a mantle of residual soils of varying thickness arising due to the weathering of the ancient rocks of the peninsular shield. Ten classes of soils have developed in the Ganga basin under different Iithological, climatic and pedogenetic conditions.
Some of the soils within the Ganga basin are highly susceptible to erosion. Such soils need adequate conservation measures and appropriate land management interventions, with an eye towards preserving the soil resource and keeping the turbidity levels of the surface water within tolerable limits. The susceptibility of each of the soil groups to erosion and the areas covered in the different states within the Ganga basin are indicated here.
Among the soil types within Ganga basin, the alluvial soil covers more than 52 per cent of the basin. The alluvial deposits of the basin not only cover the great Gangetic trough, but also extend over a sizable portion of the peninsular foreland in the form of a layer less than 3 metres thick. The entire alluvial formation is endowed with rich soil nutrients. The alluvial deposits of the Ganga and its tributaries, coming down the Himalaya and the peninsular foreland, have yielded annual harvests of crops for the past thousands of years with little significant deterioration. Besides paddy, this tract produces a wide variety of crops including wheat, jowar, bajra, small millets, pulses of different kinds, maize, cotton, jute and many other food and commercial crops.
If managed properly, the alluvial soils are highly fertile soils, capable of producing the highest possible yields of crops to feed the millions. However, these soils are sensitive to change and prone to rapid degradation and pollution.
In certain parts of the basin, the soils are already showing signs of salinity (as in Haryana), alkalinity (as in western U.P.), calcareousness (as in north Bihar) and acidity (as in West Bengal) due to overuse, long occupation and continued application of inputs like excessive irrigation water and toxic agro-chemicals of various types.
(Source: http://www.moef.nic.in/downloads/public-information/Draft%20ESA%20Volume%20I.pdf accessed on 20.06.2016)