Dry spots in golf courses: Occurrence, amelioration and prevention

Although soils are generally considered to wet readily, numerous sandy soils are actually water repellent at the surface and in the rhizosphere during dry periods. The failure to absorb water has been observed under a range of vegetation types, including grass. 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. Localized dry spot (LDS) caused by water repellent soil continues to be a problem for many golf course superintendents. We investigated this common soil condition in the greens and fairways of Dutch golf courses. Spatial variability in degree of water repellency and soil water content were studied in vertical transects by intensive sampling. Dry spots exhibited extreme water repellency (water drops remaining for more than six hours on the surface of soil samples) to a depth of more than 200 mm. Treatments with surfactants reduced water repellency in the surface layer, decreased critical soil moisture content, improved temporal infiltration rate of applied irrigation water, and increased the volumetric water content in the rootzone. To prevent soil water repellency the soil profiles have to be kept above the critical soil moisture content by regular irrigations.