Improvement of Water Movement in an Undulating Sandy Soil Prone to Water Repellency

The temporal dynamics of water repellency in soils strongly influence water flow. We investigated the variability of soil water content in a slight slope on a sandy fairway exhibiting water-repellent behavior. A time domain reflectometry (TDR) array of 60 probes measured water contents at 3-h intervals in a transect along the slope at four depths across a length of 4.5 m. A recently developed animation program was used to visualize the complex way water infiltrates into the soil. Measurements commenced 14 May 2003. Starting on 29 Mar. 2004, the same equipment was used to determine the effects of soil surfactant applications on preventing the development of water repellency and reduction of heterogeneous wetting of the soil along the slope. Additionally, soil water contents in the upper 5 cm of both the untreated and surfactant-treated areas were measured with a hand-held TDR device on five occasions between 10 May 2005 and 22 Mar. 2006. On the same dates, soil cores were taken to determine the presence of soil water repellency. The temporal dynamics of water repellency along the slope strongly influenced water flow and the appearance of preferential flow paths. Variability of the soil water content in the untreated slope following rain events is illustrated with two "movies" constructed using the actual measurements. Surfactant applications prevented the development of actual water repellency, which resulted in a more homogeneous wetting even during the summer period of 2005. The soil water contents in the surfactant-treated area are shown in a third "movie." The ability to animate the data allows better representation of the actual dynamics of water flow in the sloped test area.