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

Abstract

The impact of roots on bulk electrical conductivity was studied using a modeling approach. The presence of roots affects petrophysical relations. The effect of roots is more pronounced in sandy soil than in loamy soil. Root surface and soil–root electrical contrast affect ERT measurements the most. 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 (σ) 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 σ 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 σ 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.

Sensing the electrical properties of roots: A review

“…Process‐based multiscale numerical modeling of a soil–root continuum can thus pave a way for our understanding of upscaling mechanisms as we move from segment to plant and to field scale. A recent detailed numerical study at the plant scale shows that roots indeed affect ERT measurements and the effective electrical conductivity (Rao et al., 2019). However, explicitly representing root architecture (as in their study) in the computational domain demands a very high spatial resolution, thus increasing computational time and memory consumption.…”

“…The experimental setup is simple and typically operates at the centimeter scale. The understanding of the electrical response of single root segments is important since it is a first step towards discriminating root electrical signals from those of other soil properties and state variables, especially in combination with modeling (Rao et al., 2019).…”

“…Bulk soil resistivity is known to be strongly influenced by soil moisture content, porosity, mineralogy, temperature, and salinity level and only to a lesser extent by roots. Thus, the contrast between roots and soil depends highly on soil type and saturation state (Rao et al., 2019) and is therefore varying with time. In addition, fine roots actively take up water and nutrients and release different exudates.…”

“…Nevertheless, Rao et al. (2019) already warned that this might not always be the case. Using coupled electrical and root water uptake models, they showed that the bias in soil moisture estimates may be up to 50% when roots are not properly accounted for.…”

Efecto de la coordenada representativa de la agregación en datos de conductividad eléctrica aparente y su relación con medidas de dependencia espacial

“…Además, posee dos bobinas receptoras, separadas por 1.0 m y 0.5 m del trasmisor, que proporciona datos con una profundidad efectiva de 1.5 m y 0.75 m respectivamente cuando se coloca en la orientación del dipolo vertical; 0.75 m y 0.375 m, cuando la orientación del dipolo es horizontal, respectivamente (GEONICS, 2012). Para este caso, se tomó la información en la orientación vertical del Edwin Francisco Grisales Camargo y Aquiles Enrique Darghan Contreras 23 dipolo, contenida a una profundidad de 0.75 m (CEa-075), por ser una de las más encontradas en su mapeo debido a que en esta profundidad se encuentra gran parte del desarrollo de las raíces de los cultivos (Silva, et al, 2019;Rao, et al, 2019;Guo, et al, 2012).…”