Using polyacrylamide to control erosion on agricultural and disturbeds soils in rainfed areas

ABSTRACT: Use of anionic polyacrylamide (PAM) as an erosion control soil amendment has been studied at the U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS), National Soil Erosion Research Lab since the early 1990s. An initial field experiment in Indiana using simulated rainfall on a sloping silt loam soil found that 20 kg ha−1 of PAM could reduce sediment loss by more than 60% from the first storm event from an agricultural silt loam soil, as well as provide control from rill detachment for inflows of water up to 60 L min−1. More recent studies have examined use of PAM on areas prone to excessive erosion (highway embankments, landfill caps, etc.) to provide control while vegetation is being established. A simulated rainfall study found that 80 kg ha−1 PAM application on a 3:1 silt loam soil embankment reduced runoff by 86% and soil loss by 99% in a severe storm event (69 mm h−1 for 1 hour) on initially dry soil. The PAM continued to be effective at controlling runoff and soil loss through a series of simulated rainfall applications, reducing runoff by an average of 40% and soil loss by an average of 83% over the entire experiment. Two associated natural rainfall studies found similar erosion control benefits, as well as improved vegetation establishment. Polyacrylamide at 80 kg ha−1 was also found to be effective at preventing earthen channel erosion and degradation on a preformed trapezoidal channel at a 1% slope at inflows of water up to 760 L min−1. Application of PAM as a liquid spray that is allowed to dry on the soil surface is more effective than an application of dry PAM granules for immediate erosion control. Recent laboratory experiments have been targeted toward determining the optimal rates of PAM to control rill erosion and minimize cost.