Advances in understanding and managing water repellent soils

Water repellency occurs in most irrigated soils, but is most pronounced in coarse sands and sandy soils due to accumulation of hydrophobic compounds on soil particles or to physiochemical changes in soil organic matter. As soils dry, hydrophobic compounds polymerize and water repellency increases. Once a critical moisture content is reached soils shift from wettable to non-wettable, impacting infiltration and unsaturated flow in affected soils, and consequently water use efficiency and turf quality. Surfactant formulations were evaluated on water repellent or susceptible soils at diverse test locations in the United States, the Netherlands and Australia. Treatments reduced water repellency (measured as water drop penetration time), shifted critical moisture content, improved temporal infiltration rate of applied irrigation water, and increased rootzone volumetric water content.