Measured saline and sodic solutions effects on soil saturated hydraulic conductivity, electrical conductivity and sodium adsorption ratio

Abstract

Hydraulic conductivity is important in the transport of water and salts in salt affected soils. The objective of this study was to determine how saturation of soil columns with saline and sodic solutions changes soil saturated hydraulic conductivity (Ksat) and subsequent salt leaching on a variety of soil textures and smectite clay content. Soil columns were capillary wetted with solutions of varying electrical conductivity (EC) and sodium adsorption ratio (SAR). Ksat was measured by infiltrating deionized water at the soil surface. Ksat as a function of leachate pore volume was fit with an exponential decay equation and a pedotransfer function was created to predict the decay coefficients. Higher salt contents in waters were more successful at increasing soil SAR as compared to low salt content waters. The pedotransfer functions performed similar to the McNeal and Simunek and Suarez models to predict Ksat change due to solution composition without the need of X-ray diffraction of the soil clay fraction. Soils with a greater clay content and specifically smectite clay content have larger changes in saturated water flow rates whether from one time wetting or under long term use of irrigation waters at high EC and Low SAR. High clay smectitic soils require careful management when they are saline-sodic and have a smaller range of safe irrigation waters to prevent reduction in hydraulic conductivity from SAR.