Polyacrylamide efficacy for reducing soil erosion and runoff as influenced by slope

Abstract

Anionic polyacrylamide (PAM) can reduce soil erosion. Slope is an important factor determining erosion rate; however, PAM guidelines have not been well developed for different slopes. The objective of this study was to evaluate the extent which 20 kg ha⁻¹ (18 lb ac⁻¹) PAM (20P) and 40 kg ha⁻¹ (36 lb ac⁻¹) PAM (40P) increase the time to initial runoff (TRO), decrease cumulative runoff (RO), and decrease cumulative sediment loss (SL) on a Mexico silt loam soil adjusted to slopes of 10%, 20%, and 40%. Soils were packed to a bulk density of 1.3 Mg m⁻³ (81 lb ft⁻³) in test beds 0.3 × 0.3 × 0.15 m (12 × 12 × 6 in) and were subjected to a 61 mm h⁻¹ (2.4 in hr⁻¹) simulated rainfall with a kinetic energy of 1.5 kJ m⁻² h⁻¹ (103 ft lb ft⁻² hr⁻¹) for 1 h. Differences in TRO and SL for all slopes and PAM rates were all highly significant, as were all two-way interactions (<i>p</i> &lt; 0.01). Applications of 20P and 40P significantly increased TRO compared to the untreated control (0P) at slopes 20% and greater but not at a 10% slope. No difference in TRO was found for soils at slopes up to 20% between 20P and 40P. The TRO was significantly greater at 40% slope for the 40P compared to the 20P application. Values of TRO with 20P and 40P were not increased at a 10% slope compared to 0P. Slope was not a factor in reducing RO. Applications of 40P for all slopes had significantly greater RO than either 0P or 20P. Polyacrylamide reduced SL for all slopes. A higher rate of PAM (40P) had less SL than a lower rate of PAM (20P) at slopes of 20% and 40%. With 40P, the reduction in SL was 72% greater than 0P at 40% slope. Therefore, slope is a critical factor in determining a PAM rate for reducing soil erosion and should be considered for proper application.