Preferential flow paths in a water repellent clay soil with grass cover

Grass-covered heavy basin clay soils in the Netherlands appeared to be water-repellent. Water-repellency in the top layers of these soils occurred mainly as a coating on the aggregates. Differences between minimum and maximum soil moisture contents were high in all the layers sampled. When the clay soil is dry, a major proportion of the water from precipitation or sprinkler irrigation may flow rapidly through shrinkage cracks to the subsoil, bypassing the matrix of the clay peds. However, preferential flow is not limited to macropore flow; irregular wetting patterns are also formed through the small pores of the matrix