From the management point of view the salt affected soils are divided into two broad categories – (1) Sodic (alkali) soils, and (2) Saline soils, though at places saline-sodic soils are also met with. However, the management of saline sodic soils will be more similar to that of the sodic soils. Such soil needs extra water for leaching of soluble salts. The sodic soils have higher proportion of sodium in relation to other cations in soil solution and on exchange complex. The growth of most crop plants is adversely affected because of impairment of physical conditions, disorder in nutrient availability and suppression of biological activity due to high pH exceeding even 10.0 and exchangeable sodium upto 90 or so. The solution salts 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, or in concretionary form or even as an indurate bed at about 1m depth. The accumulation of CaCO3 generally occurs within the zone of fluctuating water table. The dominant clay mineral is illite. The processes which target on dissolution of CaCO3 have significant role in reclamation of alkali or sodic soils. 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, Fe sometimes pose problems in 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 run-off from the adjoining areas/undrained basins. The inland saline lands are widespread in the canal irrigated, arid and semiarid regions. These soils are characterized by the presence of excess neutral soluble salts like chlorides and sulphates of sodium, calcium and magnesium. Sodium chloride is the dominant salt. High soil salinity is often accompanied by high water table, often within 2 m of soil surface. Sub soil waters are generally salty and, therefore, their use for irrigation presents major constraints. In general, these soils have good physical properties but poor natural drainage. The formation of saline soils is generally associated with rise in watertable due to introduction of irrigation and inadequate drainage.

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Laboratory Testing, Soil Behavior Modeling