Two-Dimensional Spatial and Temporal Monitoring of Soil Water Content in Maize Field Using Electrical Resistivity Tomography.

Soil water content at certain depth point can be accurately measured by Time Domain Reflectometry (TDR). 2-D (two dimensional) Electrical Resistivity Tomography (ERT) can estimate subsurface cross sectional soil water content distribution under field crops (Dider Michot et al., 2003). Recently, there are some studies combing both ERT and TDR for the determination of soil water content (Ulrike Werban et al., 2008; Iyad and Claude, 2009). TDR is used to convert electrical resistivity to soil water content, however, installation of TDR measurement sensor needs to disturb the natural soil environment. Soil water content in actual crop field shows heterogeneous distribution that depends on crop and soil characteristics (Wesenbeeck 1988). So a measurement method to monitor spatial and temporal distributions of soil water content without disturbance of the field is required.

One solution to this problem is laboratory calibration which converts electrical resistivity to soil water content. Given that electrical resistivity of soil water is influenced not only by water content but also by electrical conductivity of soil water, this conversion is not easy. The objective of this study is to understand the relationship between electrical resistivity and soil water content calibrated by the electrical laboratory conductivity of soil water. Results of this laboratory EC calibration will be applied to a maize field later.