The Potential and Actual Presence of Soil Water Repellency In Preferential Flow Paths.

Preferential flow is the rapid movement of water and solutes through soils that bypasses a large proportion of the soil matrix.  Factors that causes preferential flow include macropores, root channels and cracks.  Soil water repellency makes soils difficult to wet, thereby forcing water and solutes to flow via preferential flow paths.  The role that soil water repellency plays in development of preferential flow paths is not well understood. This study was conducted to determine whether the potential soil water repellency is related to actual soil water repellency in preferential flow paths.  Preferential flow was detected using image analysis of flow patterns visualized by dye tracers.  Samples were taken from dyed and non dyed flow paths. As well, depth and width measurments were also taken so that the precise point could be assessed for soil water repellency.  Samples were tested in the lab initially for the actual degree of soil water repellency and sub samples were oven dried to determine the water content.  The soil was then oven dried for 24 hours to obtain maximum soil water repellency and finally tested for the potential degree of soil water repellency.  The change between actual and potential soil water repellency gives an indication of how soil water repellency might alter the development of preferential flow paths.