Effect of Sodium adsorption ratio with different electrolyte concentrations on saturated hydraulic conductivity of salt affected soils of Gujarat

Abstract

Soil hydraulic conductivity depends on the composition of exchangeable cations and the composition and concentration of the electrolytes in the soil solution as well as soil texture. This laboratory experiment was conducted on salt affected soils viz P1 (Samni village-Typic Haplustert), P2 (Kalamsar village-Fluventic Haplustept), P3 (Traj village-Typic Halaquept), P4 (Saragwada village-Typic Ustorthent) and P5 (Kharad village- Vertic Haplustept) to determine the hydro-physical behaviour under different water qualities and physico-chemical parameters of the soil. Concentration and composition of the water flowing through the soil showed a marked influence on saturated hydraulic conductivity of salt affected soils. Soil pH ranged from 7.5 to 8.4 and ECe from 2.8 to 132 dS m-1. Result revealed that hydraulic conductivity increased with increasing ECe of the soil in both SAR (10 and 20 m mol1/2 L-1/2) with different TEC (10, 20, 40, 80 and 100 me L-1). The maximum Ks was observed in sandy clay loam soil with high ECe i.e. 0.213 cm h-1 in SAR 10 m mol1/2 L-1/2 with TEC 20 me L-1 and 0.152 cm h-1 in SAR 20 m mol1/2 L-1/2 with TEC 40 me L-1 as compare to clay and clay loam soils. The hydraulic conductivity decreased with increase in the ESP and decrease in the total electrolytic concentration of the soil solution, whereas this trend was not observed in clay loam soils (P2 and P3), which showed low ESP and ECe with result of least value of Ks. In clay loam soils, presence of CO3-- and HCO3- was observed very high as compared to clay and sandy clay loam soils which might be a major cause of low Ks values. Among all the cations and anions Na+, and Cl- were dominant in all the soils. The reduction in the hydraulic conductivity may be attributed to swelling and dispersion of the soil clays. Thus the study indicated that the combined effect of water quality and soil properties on saturated hydraulic conductivity (Ks) was influenced by SAR and TEC with ECe, ESP as well as the cations and anions of the soils.