Microorganisms in soil are critical to nutrient cycling, moisture retention, and supporting plant productivity, making microbial activity one of the key indicators of soil health. Electrodes in soil can measure microbial activity via electrochemical signals, which can correlate with soil health. These signals include 1) continuous current generation via chronoamperometry, 2) cyclic response via cyclic voltammetry, and 3) redox potential via open circuit potential. Previously, we demonstrated that chronoamperometric and cyclic voltammograms could serve as a proxy to distinguish between healthy and less healthy soils. However, due to the heterogeneity of soil, it remains unclear whether electrode size influences the electrochemical response. The goal of this work is to determine whether electrochemical signals retain the ability to distinguish between healthy and less healthy soils characterized by nutrient analysis and biological assays across carbon fabric electrodes of three different sizes (64 cm 2 , 16 cm 2 , 4 cm 2 ). All electrode sizes tested measured significant differences in current density and cyclic voltammograms between soil types. However, 64 cm 2 electrodes exhibited lower current density and slower response in chronoamperometry, indicating limitations in the scalability of biofilm electrodes in soil. The electrochemical signals reflecting microbial activity differentiated soil health across the tested electrode sizes.
Webster et al. (2026) studied this question.