Controlling Runoff and Erosion in Sloping Land with Polyacrylamide under a Rainfall Simulator

Most of irrigated land in semi-arid and arid areas are prone to erosion and decreased productivity if not well managed. An alternative to conservative practices to control the erosion and runoff is polyacrylamide (PAM) application with irrigation water. Most of the research for PAM application in sprinkler irrigation was done on slopes of about 2%, while sprinkler irrigation may be used on slopes of up to 10%, where PAM application in sprinkler irrigation on such slopes may result differently. This research was conducted to determine the effects of different rates of PAM (0, 1, 2, 4, and 6 kg ha−1) applied with sprinkler irrigation water followed by two sprinkler irrigations with no PAM application on runoff, soil loss, and improving infiltration on different soil surface slopes (2·5%, 5·0% and 7·5%) under rainfall simulator in laboratory. It was found that at steep slopes, higher PAM application rates are required to enhance the final infiltration rate, to reduce the runoff and soil erosion. The data also indicated that for steep slopes (up to 7·5%) higher PAM application rates as 6 kg ha−1 is required for runoff reduction especially at third irrigation. It is also indicated that a PAM application rate of 4 kg ha−1 is the most appropriate for soil erosion reduction at slopes of 5·0% and 7·5%. Furthermore, at steep slopes, i.e. 7·5%, the PAM application rates of greater than 4 kg ha−1 at first irrigation water application was required to enhance the final infiltration rate. The effect of PAM in reducing erosion was greater than in reducing runoff.