Inhibiting Water Infiltration into Soils with Cross-linked Polyacrylamide: Seepage Reduction for Irrigated Agriculture

Rodrick D. Lentz* USDA-ARS Northwest Irrigation and Soils Research Lab. 3793 N 3600 E Kimberly, ID 83341 High water infiltration rates in unlined canals, reservoirs, and the inflow end of furrows relative to outflow ends result in excessive seepage losses and reduced furrow irrigation application uniformity. This study evaluated the use of cross-linked, anionic, polyacrylamide hydrogel (XPAM), a water-absorbing, swellable polymer solid, for reducing infiltration and seepage losses though soil. Experiments 1 and 2 measured the influence of soil treatments on seepage rate in soil columns under constant-head conditions: Exp. 1 treated five soils with 0, 2.5, 5, and 10 g kg -1 XPAM; Exp. 2 applied combined XPAM (0-5 g kg-1) and NaC1 (0-5.1 g kg-1) treatments to a silt loam soil, and separately tested the effect ofXPAM granule size and treated soil layer thickness on seepage rate. In Exp. 3, a miniflume was used to determine how a 5-mm-thick, XPAM-treated (0-5 g kg1) soil layer at the inflow end of the "minifurrow" influenced water distribution. The 21-h seepage rates of all soils except the loamy sand decreased curvilinearly with increasing )(PAM rate, with maximum reductions of 87 to 94% for 5 and 10 g kg -1 XPAM rates, relative to controls. The <300-pm-diam. XPAM granules were significantly more effective than the coarser grained )(PAM for reducing seepage, and reducing the thickness of the treated soil layer from 71 to 24 mm had no significant effect on the seepage reduction obtained with XPAM. The 5 g kg1 XPAM treatment applied to inflowend miniflume soils significantly decreased the "furrow-stream" advance period and reversed the infiltration patterns observed in miniflumes, relative to controls. These XPAM treatments could potentially be used to increase the uniformity of furrow water applications and reduce seepage from unlined irrigation ponds and canals.