POLYACRYLAMIDE EFFECT ON INFILTRATION AND EROSION IN FURROWS

Surface sealing and crusting are important factors affecting runoff an d erosion in many cultivated soils. The objective of this study was to evaluate the effects of low rates of surface-applied anionic polyacry lamide (PAM) on surface sealing and crusting, water infiltration, and soil erosion. A series of experiments was conducted on a Cecil sandy l oam soil (clayey, kaolinitic, thermic Typic Kanhapludult) in ridge-fur row-type held plots (3.5 by 0.92 m). Polyacrylamide solutions containi ng 1 kg solids m(-3) and 2.5 mol CaSO4 m(-3) were sprayed onto dry soi l surfaces at 15 and 30 kg ha(-1) rates with two replicates each. Thre e simulated rains, 31 min each, were applied at an intensity of 85 mm h(-1) at 2-wk intervals. Final infiltration rates were 30 mm h(-1) for the control treatment for all three rains and were >85 mm h(-1) for t he first rain and 45 mm h(-1) for the two following rains for the PAM treatments. Total soil loss of the control was 1.62 kg m(-2) for the f irst rain, while the average soil loss of the two PAM treatments was o nly 0.03 kg m(-2). For two subsequent rains, although the differences were narrowed, soil loss from PAM was 48 to 66% less than from the con trol. The percentage of sediments >0.5 mm in the PAM treatments was 45 % greater than in the control, indicating high aggregate stability wit h PAM addition. The sediment reduction was attributed to the significa nt reduction of runoff and the prevention of rill formation due to PAM addition. Based on this study, surface application of PAM at a rate o f 15 kg ha(-1) controlled surface sealing and crusting and therefore r educed runoff and erosion.