Exchangeable Na, polymer, and water quality effects on water infiltration and soil loss

Increasing exchangeable sodium percentage (ESP) contributes to increased soil dispersion and swelling of clay, which reduces the infiltration rate and increases runoff. Synthetic polymers are available that may decrease soil dispersion. A study was conducted to determine the effect of three polymers dissolved in water at 10 or 50 mg L‐1 concentrations and applied through a rainfall simulator on the infiltration rate, erosion, and soil migration through the layer of a soil at ESP equal to 8.5 and 30.6. The polymers were a cationic polysaccharide and two anionic polyacrylamides with different negative charge densities. The infiltration rate decreased with time and approached a final steady‐state infiltration rate (FIR). The runoff water and associated sediment were captured and measured. Water coming through the soil layer and the amount of particulates contained in the water were measured. The FIR was significantly lower for the soil at ESP equal to 30.6 than at ESP equal to 8.5. There was no statistically significant effect of the polymer type or concentration on FIR. The amount of soil loss through erosion was significantly affected by the soil ESP, polymer type, and polymer concentration of the polymer application. More soil was in the runoff for the higher ESP than for the lower ESP. The polymer treatment effects on soil loss were in the following order: cationic polysaccharide > untreated > low anionic PAM > higher‐charged anionic PAM. Soil loss from application of the polymer at 50 mg L‐1 was significantly less than at 10 mg L‐1. The amount of soil migrating through the soil layer with the percolate was significantly higher for the higher ESP soil, whereas there was no significant effect of polymer treatment on this parameter.