Impact of Maize Roots on Soil–Root Electrical Conductivity: A Simulation Study

Abstract

Electrical resistivity tomography (ERT) has become an important tool for studying root-zone soil water fluxes under field conditions. The results of ERT translate to water content via empirical pedophysical relations, usually ignoring the impact of roots; however, studies in the literature have shown that roots in soils may actually play a non-negligible role in the bulk electrical conductivity (s) of the soil–root continuum, but we do not completely understand the impact of root segments on ERT measurements. In this numerical study, we coupled an electrical model with a plant–soil water flow model to investigate the impact of roots on virtual ERT measurements. The coupled model can produce three-dimensional simulations of root growth and development, water flow in soil and root systems, and electrical transfer in the soil–root continuum. Our electrical simulation illustrates that in rooted soils, for every 1% increase in the root/sand volume ratio, there can be a 4 to 18% increase in the uncertainty of s computed via the model, caused by the presence of root segments; the uncertainty in a loam medium is 0.2 to 1.5%. The influence of root segments on ERT measurements depends on the root surface area (r = ~0.6) and the s contrast between roots and the soil (r = ~0.9), as revealed by correlation analysis. This study is important in the context of accurate water content predictions for automated irrigation systems in sandy soil.