Modeling Effective Electrical Properties of Soil-Root Continuum to Discriminate Root Traits

Electrical Impedance Tomography is a promising tool for the soil-root research and can be used to phenotype root systems. Here, we run finite element models of soil-root continuum, with explicit root architecture in the finite element mesh, to understand whether the root system can be characterized using effective electrical properties. The measured IP spectra of the maize root segments at different frequencies (IP spectra) is included in the modelling study. The roots were explicitly represented with their frequency dependent electrical properties in the finite element mesh, including the properties of cortex and steel. Effective properties and anisotropy are examined for different synthetic root architecture generated in Crootbox software. We then relate the modelled electrical anisotropy factor to the geometrical anisotropy factor of root structure. To formulate geometrical anisotropy factor, we discuss different approaches such as ratio of averaged slopes of root segments in two perpendicular directions, ratio of correlation length from variograms of root length density and others. We also discuss, how we can relate the above-mentioned geometrical anisotropy factor of root networks to the simulated electrical anisotropy of effective conductivity of soil-root continuum. The understanding of relation between geometry of root network, electrical conductivity contrast between soil-root and effective electrical property of soil-root continuum is very important to monitor rooted zone via electrical methods and our modelling results helps to give insight.