Improved horizontal installation of large soil moisture content sensors and interpretation of their readings in terms of preferential flow

Soil moisture content was measured by TDR sensors Aqua-Tel-TDR (Automata, Inc., today McCrometer CONNECT) in a loamy Chernozem on carbonate-rich loess substrate. The sensors, wrapped in slurry made of local soil and water, were installed horizontally into pre-made holes. The bias caused by imperfectly filled gaps between the wall of the hole and the sensor surface was reduced by field calibration. The same gaps made it possible to detect the preferential flow in soil macropores, due to which the reflectometric readings were perceivably higher than analogous readings before percolation events and sometimes higher than the native soil porosity. One typical event is presented. It is envisaged that sensors of this type can be used for semi-quantitative estimation of the preferential flux density, e.g. with the help of dual or multiple porous medium models or the momentum dissipation theory.