Effect of River Sand on the Permeability of a Sodic Soil

The effect of river sand on the permeability of a highly sodic soil has been studied under laboratory and field conditions. A sharp decrease in hydraulic conductivity occurred with time where sand and soil were mixed in the ratio of 175: 25. With further increase in the amount of soil, there appeared not much difference in hydraulic conductivity and was nearly constant at 0.1 × 10⁻² cm/hr, which was comparable to the treatment containing soil alone. Covering the soil with 1, 2 and 3 cm thick sand layer increased the saturated hydraulic conductivity by 48, 63 and 97 times, respectively, whereas mixing of sand in different amounts in the upper 7.5 cm soil layer did not alter the permeability characteristics compared to the control. At 168 hours the cumulative intake in the treatments where sand was mixed at the rates of 0, 9 and 18 kg/m² was 10.86, 11.48 and 10.72 cm, respectively. When different depths of sand layers were surface applied, the cumulative intake in 191 hours was 9.35, 12.12, 12.06 and 12.58 cm under control, 2, 4 and 6 cm sand layers, respectively. It is discussed that the clay displacement and subsequent clogging of the pores created by sand additions possibly resulted in reduced water flux, whereas, the surface application of sand prevented the formation of crust just below the sand layer resulting in higher water intake by the soil.