Pedophysical Study of Electrical Properties and Water Content, Laboratory and Field Experiments

Within the iSOIL project we are developing a mobile multisensor platform to gain fast, accurate areal information of soils at the field scale. The measured geophysical attributes (e.g. electric, electromagnetic) need to be linked to soil parameters (e.g. clay and water content) via geophysical pedotransfer functions, GPTFs. These could either be empirical (e.g. Archie and Topp et al. Equations) or physically-based (e.g. mixing and effective medium models). Our interdisciplinary activities aim to develop robust GPTFs using diverse laboratory and in situ experiments. In laboratory experiments we investigated the influence of water content on di-/electrical measurements. The dried samples collected from different sites and depths were uniformly saturated with rain water in steps of ~2% pore volume. For each step we measured georadar reflections and geoelectrical resistivity as well as water content and temperature. Also independent permittivity measurements were conducted to validate GPTFs results. The geophysical results were complemented by a suite of standard soil parameters determined on the samples. From these lab and field data the relationship of water content with respect to both the dielectric permittivity and electric resistivity are established. Different empirical and mixing models are fitted to the data and discussed.