Evaluation of Polyacrylamide (PAM) Effectiveness in Proving Aggregate Stability and Decreasing of Soil Erosion in Marly Hillslopes of Zanjan Province

The objective of this study was an evaluation of optimum application rate of PAM for stabilization of unstable soil slopes (hills). Cultivation and cropping on the sloping hills without taking proper and suitable conservative measures causes irreparable damages to agriculture because of soil degradation and the resulting decrease in crop productivity. Experiments were conducted on soil samples taken from unstable sloping marly hills of Sarcham area in Zanjan Province employing a rainfall simulator equipped with an oscillating noze and a small 1×1 meter tilting flume’s tray (adjustable between 0 to 50 percent slope) in Research Institute of Forests and Rangelands of Iran. The treatments were studied at different slopes (15, 20, 25 and 30 %) and rain intensities (25, 50 and 75 mm h-1) to investigate their effect on runoff and on the resulting sediment formation. Results showed that application of different rates of PAM on the steep slopes did not so much affect runoff reduction and/or splash erosion. However applying different levels of PAM did have significant effect on reducing sediment concentration and accumulation. PAM application also increased shear strength of the soil surface due to its improving of aggregate stability. Results obtained from measurements of aggregate stability index and mean weight diameter of soil particles, in various rates of PAM application, showed that use of PAM whit its improving soil physical properties, will reduce soil surface sealing. Some effective parameters in erosion processes in soils treated by PAM were estimated using multivariable linear regression. Since longevity and durability of erosion control through PAM application is short, it is speculated that applications of PAM following major rainfall events may be a successful preventive measure of soil erosion and degradation.