Effect of Irrigation with Saline Groundwater Containing Silica on Crust Formation in Arid Zone Soils

Underground waters of western Rajasthan very often contain high amounts of dissolved silica. The average concentration of silica in waters from alluvium, phyllite and granite rock formation was 31.2, 20.3 and 31.8 ppm, respectively and the samples from phyllitic rocks were most saline (EC 6.9–20.2 mmhos|cm). The dissolved silica was adsorbed almost instantaneously on both fine and coarse textured soils and the adsorption exhibited a highly significant relationship with its concentration in water (r=0.986 for loam and 0.999 for pure sand). Adsorption reaction s involved high free energies (ΔG) being 6.11 k. Cal.|degree|mole for loamy soils which indicated’ involvement of chemical type of forces. Increased strength of soil crust was found to be associated with higher amount of silica deposition (from irrigation water). Very high degree of correlation (r=0.98 3 to 0.994) was found between concentration of silica in irrigation water and the soil crust force.