Soil Loss Reduction From Application of Polyacrylamide On Different Slopes.

Use of polyacrylamide (PAM) for erosion control in rainfed areas is an emerging conservation practice. Use of PAM decreases erosion on hillslopes. Slope steepness is an important factor used in soil erosion models. However, guidelines for PAM application for different slopes have not been developed. The objective of this study was to evaluate the benefits of 20 kg ha^‑1 PAM (20P) and 40 kg ha^-1 PAM (40P) solutions on disturbed silt loam soil with selected slopes of 10%, 20%, and 40%. Measured variables included (1) time to initial runoff (RO_t), (2) cumulative runoff (RO_c), and (3) cumulative sediment loss (SL_c). Soils were packed to a bulk density of 1.3 Mg m^-3 in 0.3 x 0.3 x 0.15 m test beds and subjected to 60 mm h^-1 of simulated rainfall for 60 min. Differences in RO_t, RO_c, and SL_c for the slopes and levels of PAM were all highly significant, as were all two-way interactions (P<0.001). The SL_c increased linearly with slope for all levels of PAM. The 20P and 40P treatments at a 10% slope both significantly reduced SL_c, however, no difference in SL_c was found between them. For the 40% slope the 20P and 40P treatments significantly reduced SL_c by 20% (1,188 g m^-2 h^-1) and 54% (682 g m^-2 h^-1) compared to the untreated soil (1,485 g m^-2 h^-1; P<0.001), and were significantly different from each other. The 40P treatment was 34% more effective at more than 20% slopes vs. the 20P treatment. Results suggest the need to increase PAM rates with increasing slope.