Soil Water Repellency

Although soils are normally thought of as being readily wettable by rainfall or irrigation, it is not uncommon for soils to behave in a water-repellent (hydrophobic) manner (Figure 19.1). ¤is resistance of soils to wetting when in contact with water can persist from as little as a few seconds to, in extreme cases, months (e.g., King, 1981; Dekker and Ritsema, 1994; Doerr and ¤omas, 2000). Water-repellent behavior is typically conned to the organically enriched upper few centimeters or decimeters of the soil and tends to be both spatially and temporally highly variable. It can develop when soil moisture falls below a critical threshold and oen disappears aer prolonged wet periods (Dekker et al., 2001).