Occurrence of gypsiferous and associated soils in Bikaner District of Rajasthan and evaluation of their land use from field pedogenic characteristics

Occurrence of gypsiferous soils in India has received meagre attention. Information on their land use potential is virtually negligible. The present study attempts to investigate the genesis of these soils and to evolve criteria that could be diagnostic for a rapid appraisal of their suitability for crop production. Six pedons, representative of a physiography characterized by different intensities of sand dune formation and inter-dunal plain, were studied to (i) identify pedogenic gypsum and to study its characteristics, and (ii) to identify processes responsible for the formation of gypsiferous soils in the arid region. Presence of appreciable gypsum content coupled with high content of soluble Ca²⁺ and SO₄²⁻ions in the saturated paste extracts point to the possibility of formation of a gypsic horizon in the inter-dunal area having high gypsum-bearing parent material over a stable landform. Dissolution and translocation of gypsum from higher elevation to the inter-dunal area and its redistribution in the soil solution due to wetting and drying cycles may also have resulted in pedogenic gypsum accumulation. However, such an observation is not always true since in the same landform non-gypsiferous soils are also found to occur. This has been attributed to the fact that in presence of high soluble salts of similar ions and calcium bicarbonate and sulphate, the solubility of gypsum decreases thereby preventing its expression. Suitability of soils for either semi-tolerant crops is dependent on (i) the depth at which gypsum accumulation occurs; (ii) the depth of impervious layer, and (iii) the extent of crop tolerance. Based on these criteria, suitability of soils for crop growth has been worked out.