Effects of Polyacrylamide in Controlling of Splash Erosion from a Soil induced Freeze-Thaw Cycle

Introduction: The capability of a soil to resist erosion depends on soil-particle size and distribution, soil structure and structural stability, soil permeability, water content, organic matter content, and mineral and chemical constituents. Among many affecting factors on aforesaid characteristics, the freezing-thawing processes may considerably affects. Freeze–thaw fluctuation is a natural phenomenon that is frequently encountered by soils in the higher latitude and altitude regions in late autumn and early spring. Effects of freezing and freezing-thawing phenomena on soil erosion and sediment yield are important. Nevertheless, soil conservation under these phenomena by using different methods as well as soil amendments has not been yet considered. Surface application of anionic polyacrylamide (PAM) in solution has been found to be very effective in decreasing seal formation, runoff, and erosion.PAM stabilizes soil structure due to the ability of the polymer chains to adsorb onto clay particles and bridge them together forming stable domains. This adsorption can be a result of interactions between the negatively-charged functional groups of the PAM molecules and the positively-charged edges of clay minerals, orexchangeable polycations (mainly Ca2+) acting as ‘bridges’ between the negative charges of the PAM's functional groups and the negatively- charged planar surfaces of the clay. The PAM is adsorbed on the external surfaces of the aggregates and binds soil particles far apart together, thereby were shorter and evidently less effective in enhancing increasing their resistance to splash by raindrop impact and detachment by runoff. A lot of research work focused on freezing effects in soils on aggregation or increase aggregate stability and emphasis corresponding effects. But the effects of application of soil amendments on soil induced freeze and thaw cycle have not been studied yet. Materials and Methods: The present study evaluated the performance of PAM in controlling freeze-thaw cycle effects on splash erosion from a silty loam soil. A freeze-thaw cycle was simulated in Soil Erosion and Rainfall Simulation Laboratory of TarbiatModares University. The present study was conducted under controlled laboratory conditions with a simulated rainfall. The maximum efforts were made to mimic natural conditions to get access to results with high level of fidelity. Towards this attempt, air and different soil depth temperatures were analyzed in natural conditio