SALINITY EFFECTS ON HYDRAULIC PROPERTIES OF SOILS

Abstract

Laboratory determinations of saturated hydraulic conductivity and infiltration rate were conducted with four soils varying in texture from sand to clay and with five saline-sodic waters. The waters varied in total dissolved solids from 1250 to 15000 milligrams per liter and in SAR from 16 to 57 and were representative of saline groundwaters in New Mexico. Saturated hydraulic conductivities of the soils were not significantly affected by water quality if these waters were the sole source of irrigation water. Nevertheless, even small additions of high-quality water (“rains”) to soils previously equilibrated with the saline-sodic waters significantly decreased soil permeability. Dispersion and short- or longdistance transport of clay apparently clogged conducting pores when “rain” was introduced. Swelling was an important mechanism in reducing soil permeability only in the clay soil. The data suggest that, when saline-sodic water is the dominant irrigation source and is supplemented by “rains,” (1) all waters could be used on very sandy soils, (2) no saline-sodic waters should be used on fine-textured soils, and (3) slightly sodic, but not highly sodic, waters could be used on medium-textured soils.