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Dep. of Soil and Water Sciences, The Hebrew Univ. of Jerusalem, P.O. Box 12, Rehovot 76100, Israel
* Corresponding author(yonachen{at}agri.huji.ac.il).
Soil water repellency is known to be a dynamic property, which varies in the short term or between seasons. In the short term, its temporal nature is often studied based on soil water content, assuming that it is reestablished after the soil dries out. In this study, we examined the reestablishment of soil water repellency after wetting and subsequent drying. The reestablishment process was studied on: (i) natural water-repellent soils (WRS) subjected to different leaching rates; and (ii) wettable sand subjected to wettingdrying cycles with dissolved organic matter (DOM) solution. After air drying, the soils were packed in columns, rewetted, and from the maximum height of capillary rise for the target soil (Heq1) and that of a "reference soil" (Heq0), the equilibrium (static) contact angle (
eq1) was calculated, assuming that for the reference soil the contact angle
eq0 = 0. Increasing the leaching fraction of an initially WRS resulted in a decrease in
eq1 values. For an initially wettable soil, increasing wettingdrying cycles with DOM solutions resulted in an increase in
eq1. The variations in cos
eq1 were reflected in a similar ratio for the capillary-pressuresaturation relations (CSR). The prediction from scaling the "reference soil" CSR curve by cos
eq1 was found to be satisfactory, but more accurate where the effective saturation S <0.5. At S > 0.5, organic matter is more likely to detach and dissolve, changing the properties of the soil solution by altering its surface tension and the soil particles' surface, i.e.,
eq1.
Abbreviations: CSR, capillary pressuresaturation relations DOC, dissolved organic carbon DOM, dissolved organic matter MED, molarity of ethanol droplet OM, organic matter WDPT, water drop penetration time WRS, water-repellent soil
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