Yu, J., Institute of Water Resources, Huhhot, Inner Mongolia, China
Lei, T., Inst. of Soil and Water Conservation, Chinese Acad. Sci./Min. Water Rsrc., Yangling, Shanxi Province, 712100, China
Shainberg, I., Inst. of Soil, Water,/Environ. Sci., Agric. Research Organization (ARO), Volcani Center, P.O. Box 6, Bet Dagan 50-250, Israel
Mamedov, A.I., Inst. of Soil, Water,/Environ. Sci., Agric. Research Organization (ARO), Volcani Center, P.O. Box 6, Bet Dagan 50-250, Israel
Levy, G.J., Inst. of Soil, Water,/Environ. Sci., Agric. Research Organization (ARO), Volcani Center, P.O. Box 6, Bet Dagan 50-250, Israel

Seals formed at the soil surface during rainstorms reduce rain infiltration and cause runoff and erosion. Surface application of anionic polyacrylamide (PAM) in solution has been found to be very effective in decreasing seal formation, runoff, and erosion. The objective of this study was to investigate the effect of surface application of granular PAM (10 and 20 kg ha-1) and gypsum (2 and 4 Mg ha-1) on the infiltration rate (IR) and soil erosion from a silty loam (Calcic Haploxeralt) and sandy clay (Typic Chromoxerert) during simulated distilled water rainstorms. Mixing dry PAM with the upper 5 mm of the soil surface reduced slightly the IRs, and reduced significantly soil erosion from the two soils. Spreading gypsum at the soil surface doubled the final IR compared with that of control and reduced erosion slightly. Spreading dry PAM mixed with gypsum was very effective in increasing the rain IR and reducing erosion. Mixture of 20 kg ha-1 PAM and 4 Mg ha-1 gypsum increased the final IR of the two soils by four times and reduced erosion to 30% that of the control. Gypsum added to the erosion benefits of PAM by increasing infiltration and decreasing runoff. However, mixing gypsum with dry PAM decreased the beneficial effect of PAM in reducing erosion in the silty loam soil. The mechanisms responsible for the specific effects of PAM (mixed with soil and gypsum) on rain infiltration and soil losses are discussed.