Polymer effect on infiltration and erosion of sodic soils

Runoff from irrigated sodic soils is a common phenomenon in arid and semi-arid climates. The effect of a low-charge polysaccharide (LCCP) on infiltration rate (IR) and runoff on two red apedal soils was studied using an irrigation simulator. One was a structurally stable soil from Cedara In Natal and the other, from Irene in the Transvaal, was of a much lower stability. Application of the local tap water (TW) of EC 0.4 dS m⁻¹ represented the control treatment. The polymer was applied in suspension to this water, the soil dried for 72 h, and then TW applied. The polymer treatment maintained a higher IR and lower soil loss than TW treatments for the two soils and various ESP levels. For both soils, the greatest effect of the polymer was obtained at the lowest ESP. However, the residual effect of the polymer on IR and soil loss during the second application of TW was not meaningful. Higher IRs due to polymer application always resulted in lower soil losses. An exponential regression between soil loss and the final IR was obtained. Inasmuch as sodic soils tend to produce high runoff during irrigation, the application of LCCP through the irrigation system could be considered.