Effects of superabsorbent polymers on the vertical infiltration of soil water with sand mulching

Abstract

Superabsorbent polymer (SAP) is a kind of polymer with advantages like high water absorption and conservation. We studied the effect of various concentrations of SAPs on the infiltration of soil water with sand mulching. Five soil columns with surface sand mulch and evenly distributed SAPs at concentrations of 0, 0.1, 0.2, 0.5 and 1.0% were tested. The SAPs slowed the migration of the wetting front and thus the rate of infiltration of water, and the higher the SAP concentration, the slower the migration. The relationship between the wetting front displacement and time could be described by a logarithmic function, $Z_{f} = at^{b}$. The amount of cumulative infiltration was inversely proportional to the amount of SAPs. The final cumulative infiltration was proportional to the amount of SAPs, within a limited range. The relationship between cumulative infiltration and time was described by a power function, $I = ct^{d}$. The relationship between wetting front displacement and cumulative infiltration could be characterized by a linear equation, $I = KZ_{f} + E$, indicating that the rate of cumulative infiltration increased with the amount of SAPs for the same infiltration depth, which satisfied the Kostiakov model ($i = Bt^{ - A}$). High concentrations of SAPs strongly inhibited the infiltration of water. The infiltration rate of soil water was optimal at a SAP concentration of 0.2%, which effectively increased the amount of water in the soil.