Characteristics and morphogenesis of salt-affected soils in southeastern arid Rajasthan

Aerial photographs coupled with ground check and laboratory analysis have helped in mapping of four categories of salt affected soils located in the southeastern tract of arid Rajasthan. The categories are (1) Natural saline soils (2) Relict saline soils (3) Secondary salinized soils due to high water table and (4) Secondary salinised soils due to highly saline water use for irrigation Salinity in natural salt affected soils is mostly sodium chloride followed by sodium-calcium chloride and sodium-chloride-sulphate type. The distribution of the natural salt affected soils along the natural drainage or inconspicuous depressional areas suggest that their occurrence is due to insufficient surface drainage. Further, the pattern of distribution indicates that the origin of salt is within the catchment itself. Deep ploughing and application of organic material have reversed the upward flux of salts and improved the soils. This phenomenon also seems to explain the large occurrence of soils of relict salinity.