Sprinkler irrigation runoff and erosion control with polyacrylamide - laboratory tests

Many semiarid and arid soils are prone to irrigation-induced erosion. Polyacrylamide (PAM) greatly reduces erosion from furrow irrigation. We hypothesized that PAM applied via sprinklers will provide erosion control and benefit water infiltration and aggregate stability. Screened (6.4 mm) Rad silt loam (coarse silty, mixed, superactive mesic Durinodic Xeric Haplocambid) was placed in 1.5 by 1.2 by 0.2 m steel boxes with 2.4% slope. An oscillating nozzle, 3 m above the soil, produced a median drop size of 1.2 mm diameter. We applied 0, 1, 2, 4, and 6 kg ha-1 PAM in 20 mm of water in the first irrigation, followed by two 20-mm water-only irrigations. In a second test, we applied 0, 2, and 4 kg ha-1 PAM in 8 mm of water in the first irrigation, followed by two 20-mm water-only irrigations. Two kilograms per hectare PAM in the first 20-mm irrigation reduced runoff 70% and soil loss 75% compared to control. Polyacrylamide in 8 mm of water was less effective. Polyacrylamide in the 20-mm irrigation did not affect tension infiltration; PAM in the 8-mm irrigation doubled tension infiltration following the third irrigation. Wet aggregate stability following the first irrigation was greater in all PAM treatments than on the check. With 2 kg ha-1 PAM in the 20-mm irrigation, it was 55%; in 8 mm, 77%. Polyacrylamide applied in the first irrigation at low rates effectively reduced runoff and erosion. Erosion was more effectively controlled than runoff