Net Infiltration and Soil Erosion Effects of a Few PPM Polyacrylamide in Furrow Irrigation Water

Furrow irrigation-induced erosion, seal formation, and reduced net infiltration are severe problems in the United States of America (USA) Pacific Northwest. High molecular weight (10^7 g mol-1), anionic (18% charge density) polyacrylamide (PAM) is a potent flocculent. Economical PAM application strategies can reduce seal formation, runoff and erosion in furrow irrigation. Three years of studies verified this for 3 soils. Field slopes were 0.5-7.0%. Furrow lengths were 150- 250 m and inflow rates were 12.8-37.8 L min-1 . PAM reduced erosion by 43 to 99% for various application strategies using as little as 5 ppm PAM in furrow advance water with renewal of 5 ppm PAM for 5 minutes of each subsequent hour of irrigation. PAM stabilized net infiltration at higher rates by reducing seal formation. PAM increased the lateral wetting extent by 25% and net infiltration by 15% compared to controls. PAM efficacy varied with concentration, duration of furrow exposure, and flow rate. Furrow-bottom crusts of similar soil strength formed in PAM-treated and control furrows, but their associated seals produced different net infiltration