The infiltration of rainfall into bare soil was studied in field and laboratory experiments on two soil types in Israel. The main governing process is the formation of crust with an hydraulic conductivity several orders of magnitude lower than that of the soil profile. The decrease in conductivity is attributed to the organization of a very thin layer on the soil surface. The sealing efficiency of the crust is achieved by suction forces which arrange soil particles, probably clay, into a continuous, dense layer. The decrease in flux through the crust creates conditions of unsaturated flow in the soil profile below the crust. The dynamics of the hydraulic relationship between the soil profile and the crust during a rain storm was analyzed by means of an analytical model.
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The experimental work for this study was carried out by Pier Brussel and Paul Schaap, graduate students from the University of Wageningen, The Netherlands. We thank them for the excellent work they have done.