Electromagnetic Determination of Soil Water Content Using TDR: II. Evaluation of Installation and Configuration of Parallel Transmission Lines

Abstract

Time‐domain reflectometry (TDR) applied to parallel transmission lines in soil was used to measure the soil water contents during infiltration, drainage, evaporation, and rising water table conditions in a 1.05‐m column of silt loam soil in the laboratory. Three types of installation and several types of transmission lines were evaluated. Comparisons of volumetric water content from gravimetric samples and from TDR showed differences were always 3cm⁻³. Trends of the TDR values with time showed that these differences likely resulted from soil density variations. Neither the installation method nor the design of the rods of the transmission line affected the water content values, provided there was good electrical contact with the soil. Transmission lines with discontinuities gave an effective and efficient measure of the soil water‐content profile.