Effects of a soil surfactant on grass performance and soil wetting of a fairway prone to water repellency

Summary

This study reports on the effects of applications of a soil surfactant on improvement of grass performance and wetting of a sandy golf course fairway, located near Arnhem, the Netherlands. In addition, the influence of the surfactant on soil water repellency and the nitrogen contents in grass leaves, roots and upper 18 cm of the soil profile was investigated. The sandy soil of the fairway exhibits a water repellent behaviour resulting in a lot of localized dry spots (LDS) and poor turf quality during dry periods in spring and summer. In 2012 an experimental site on fairway 10 was divided into eight plots of 2 m by 2 m. Four plots were used as control and on four plots the surfactant was applied 6 times. The effects of the surfactant were studied on the wetting of the soil by measuring the volumetric water content at depths of 0–5 cm with a hand-held Time Domain Reflectometry (TDR) device. The grass performance was estimated in 3 distinct classes with percentages of the existence of green grass. Actual water repellency was assessed by putting water drops at regular distances along soil cores which were taken to a depth of 25 cm with a small, 1.5 cm diameter, auger. Applications of the soil surfactant resulted in dramatically improved soil wetting and turfgrass performance. Surfactant applications also resulted in more homogeneous wetting of the soil, reduced development of water repellency and preferential flow paths, and higher N concentration in soil. Since microbial mediated N mineralization is affected by moisture content, the higher N concentrations in the soil are thought to be related to the higher and more homogeneous moisture levels in the treated versus untreated plots. In addition to improved moisture availability, the better turf performance is likely affected by the increased plant available N in the soil which resulted from the more desirable and uniform moisture levels.