Levy, G.J., Institute of Soils and Water, ARO, The Volcani Center, P.O. Box 6, Bet Dagan, 50250, Israel
Agassi, M., Soil Erosion Research Station, Rupin Institute, P.O. Emeq Hefer, Israel

Low infiltration rate and high levels of soil erosion are critical problems in many soils worldwide. Amendment of soils with organic polymers could alleviate these problems. The objective of the present study is to investigate the effects of polymer molecular weight and the degree of drying on the infiltration rate of, and erosion from, three different soil types from Israel. A solution of high-molecular-weight (2xl07 Da) or low-molecular-weight (2xl05 Da) negatively charged polyacrylamide (PAMh and PAMl, respectively) was added to the surface of soil samples packed in trays, at a rate of 20 kg ha-1. The soil samples were allowed to dry to varying degrees and were then exposed to 60 mm of simulated rain during which infiltration rate and soil loss were determined. The ability of the polymer to maintain high final infiltration rates (FIR) depended on its molecular weight and the clay content of the soils. In the coarse- and medium-textured soils, the PAMh was more effective than the PAMl in maintaining high FIR. In the fine-textured soil, the effects of both polymers on FIR were comparable; the use of the PAMl is therefore preferable since it is easier to handle. Both polymers had reduced soil loss comparably. The effects of drying were similar for both polymers: the FIR and soil loss values with the intermediate degrees of drying were higher and lower, respectively, than they were with the no-drying or complete-drying treatments. © 1995 CSIRO. All Rights Reserved.