Effects of surfactant treatments on the wettability of the surface layer and the wetting patterns in a water repellent dune sand with grass cover

This study evaluates the effectiveness of a new surfactant formulation (Primer R604) for amelioration and management of soil water repellency in a dune sand, as measured with the water drop penetration test, and soil moisture content and wetting rate assessments. A dune sand with grass cover with a history of extreme water repellency was treated with 185 ml of surfactant in 7 l of water) per 100 m2. Treatment was applied three weekly from 22 April until 23 November 1999. Soil samples were taken at six depths in trenches in the treated and untreated plot over a seven-month period beginning with the initial treatment application on 22 April 1999. Surfactant treatment significantly reduced soil water repellency in the surface layer of the plot when compared with the untreated control. As a consequence, an increase in the wetting rate and higher soil water contents have been found for the surface layer of the treated plot. However, the surfactant did not improve the uneven moisture distribution in the soil below the surface layer.