Diagnosis and Management of Poor Quality Water and Salt Affected Soils

Abstract

Salt-affected soils in India are broadly placed into two broad groups; sodic (alkali) soils and saline soils. There are certain specific situations where saline-sodic soils also do exist. Since the management of saline sodic soils will be more similar to that of the sodic soils, they are generally grouped with the sodic soil category. The only management difference for their reclamation is that such soil needs extra water for leaching of soluble salts before amendment application. The sodic soils have higher proportion of sodium in relation to other cations in soil solution and on the exchange complex. Growth of most crop plants on sodic soils is adversely affected because of impairment of physical conditions, disorder in nutrient availability and suppression of biological activity due to high pH, exceeding even 10 in severe cases, and exchangeable sodium percentage of up to 90% or so (Kanwar and Bhumbla, 1969). Salt solutions contain preponderance of sodium carbonates and bicarbonates capable of alkaline hydrolysis, thereby saturating the absorbing complex with sodium. The sodic soils of the Indo-Gangetic plain are generally gypsum (CaSO4 ·2H2O) free but are calcareous, with CaCO3 increasing with depth, which is present in amorphous form, in concretionary form, or even as an indurate bed at about 1 m depth (Table 1). The accumulation of CaCO3 generally occurs within the zone of fluctuating water table. The dominant clay mineral is illite. The processes which target the dissolution of CaCO3 have significant role in reclamation of alkali or sodic soils. Crops like rice helps in reclaiming sodic soils (Chhabra and Abrol, 1977). These soils are deficient in organic matter, available N, Ca, and Zn. Certain micro-nutrients present problems of either deficiency or toxicity. Toxicities of Al, Mn, and Fe sometimes pose problems for wheat when over- irrigated and results in yellowing of the crop. The major factors responsible for formation of alkali soils in the Indo-Gangetic region include: irrigation with ground waters containing excessive quantities of carbonate and bicarbonate ions, rise in groundwater due to introduction of canal irrigation and salt laden runoff from the adjoining areas and undrained basins.