Dependence of Saturated Hydraulic Conductivity on Dispersion, Swelling and Exchangeable Sodium under Different Quality Waters

Effects of water quality on saturated hydraulic conductivity, dispersion, swelling and exchangeable sodium build-up in clay (Typic Haplustert), clay loam (Vertic Haplustept) and silt loam (Lithic Ustorthent) soils were studied. Soil samples were equilibrated with twenty-four water quality combinations encompassing four electrolyte concentrations (TEC) ranging between 5 and 50 me L−1; and six sodium adsorption ratios (SAR) ranging between 2.5 and 30 m mol½ L−½. Saturated hydraulic conductivity ranged from 0.009 to 0.157, 0.016 to 0.235; and 0.453 to 22.76 cm h−1, dispersion index from 11.6 to 26.0, 8.3 to 24.9 and 5.7 to 13.2 per cent, coefficient of linear extensibility from 0.05 to 0.21, 0.03 to 0.14; and 0.007 to 0.032; and exchangeable sodium percentage from 2.23 to 20.0, 3.18 to 24.55; and 4.26 to 32.4 in clay, clay loam and silt loam soils, respectively. Dependence of saturated hydraulic conductivity on water quality parameters (TEC and SAR) and soil properties (dispersion, swelling and exchangeable sodium) was also studied. Clay and clay loam soils were equally sensitive to the changes in TEC only. Multiple regression equations indicated the significant dependence of saturated hydraulic conductivity on ESP in all the soils. Dispersion and swelling were found to be the important processes governing the changes in saturated hydraulic conductivity of clay and clay loam soils. However, changes in saturated hydraulic conductivity were mainly governed by dispersion in silt loam soil.