Interactions between water quality and polymer treatment on infiltration rate and clay migration

Abstract

The electrical conductivity (EC) and sodium adsorption ratio (SAR) of irrigation water significantly affect water transmission properties of soil. Commercially produced polymers which are soluble in water may potentially mitigate the negative consequences of water quality on infiltration rate. Waters were synthesized to have combinations of EC equal to 0.5, 2.0 and 5.0 dS m −1 and SAR of 5, 15 and 25. These waters were applied through a laboratory scale rainfall simulator to 12 × 20 cm trays containing soil. Untreated and treated waters with 10 mg L −1 concentration of a cationic polysaccharide were used in the study. Untreated waters were applied to uncovered soil or to soil covered with fiberglass sheets 0.5 cm above the soil to disrupt the impact energy. The polymer treated waters were only applied to uncovered soil. The steady state infiltration rates were significantly affected by SAR and EC with the trend toward increasing infiltration rate with increasing EC and/or decreasing SAR under all conditions. Impact energy greatly reduced the infiltration rate as compared to no impact energy. The polymer treatment significantly increases the infiltration rate for each water. The relative beneficial effects of polymer tended to be greater with increasing EC and/or decreasing SAR. The clay in runoff and leachate had several significant interactions between waters and treatments. Treatments that tended to produce more fine particulates leading to crust formation and reduced infiltration rate tended to have less clay in the runoff and leachate. Apparently crust formation partially inhibits clay migration.