SALINITY EFFECTS ON YOLO LOAM HYDRAULIC PROPERTIES

Abstract

We examined the salinity effects on water movement in unsaturated Yolo loam through measurements of soil-water retention, soil-water diffusivity, hydraulic conductivity, and Philip's sorptivity (Philip 1969) in columns of soil wetted with water containing 15, 5, and 0 meq/liter with sodium adsorption ratio (SAR) values of 0, 5, and 15 (meq/liter)1/2. Effects of salinity on diffusivity, conductivity, sorptivity, and retention increased as soil water content increased. Except for water retention, values of these hydraulic parameters decreased as the sodium percentage of soil increased or the wetting solution concentration decreased. Estimates of hydraulic conductivity based on soil-water retention and soil-water diffusivity overestimate values of saturated hydraulic conductivity in part because of soil swelling in the retention measurements and lack of chemical equilibrium during wetting front advance in the diffusivity measurements. The results presented herein enable salinity effects to be incorporated into soil physics modeling studies that use van Genutchen's model with the Mualem restriction (van Genutchen 1980).