Bulk density and water content-dependent electrical resistivity analyses of different soil classes on a laboratory scale

The goal of this study was to achieve relations between electrical conductivity and the most influential soil properties which should be transferable to natural field conditions. Electrical conductivity of soil is mainly affected by soil moisture. This, for many soil applications like determination of thermal soil properties, crucial relation is focused within this article. Electrical conductivity was measured in dependency of bulk density and water content by applying a laboratory setup which enables a comparison to natural in-situ conditions. For this purpose, four different pressure loads and up to 12 saturation steps were performed on the textural soil types of sand, silt loam and clay. A comparison between electrical conductivity and saturated pore volume confirms the impact of soil moisture. For the final analysis natural conditions were specified using field capacity ranges and defined bulk densities. With these predetermined ranges of water content and bulk density a healthy regulation for defining natural conditions has been constructed. Due to this generated constraint a soil texture independent relation between electrical conductivity and soil moisture content with a correlation coefficient of r² = 0.95 has been developed. This correlation was also implemented within the developed measurement tool of the GeoSurf project for determining the thermal potential of soil.