Tracking biological and mechanical subsoil amelioration via multi-coil electromagnetic induction

Subsoil compaction limits root growth and water uptake, often amplifying crop stress during drought. Biological “bio-drilling” with deep-rooting plants is a sustainable alternative to mechanical tillage, creating stable biopores and improving soil structure and water infiltration, but assessing its long-term effectiveness remains challenging. This study evaluates the use of a multi-coil electromagnetic induction (EMI) system to monitor subsoil responses to various loosening strategies, including biological treatments (Lucerne and Ryegrass mixture) and mechanical deep loosening with or without compost incorporation. EMI surveys prior to the experiment revealed inherent soil heterogeneity, emphasizing the importance of baseline mapping for robust experimental design. To isolate management-induced signatures, an innovative data processing workflow was implemented to effectively disentangle anthropogenic structural legacies from the dominant pedological “soil memory” (i.e., inherent natural soil heterogeneity). Time-lapse surveys tracked treatment effects over subsequent cropping seasons. Complementary EMI point measurements showed a distinct negative trend in apparent electrical conductivity (ECa), consistent with soil drying associated with crop development and root water uptake. This suggests that biological and mechanical amelioration may leave lasting structural signatures in the subsoil that modify water accessibility and hydraulic connectivity, ultimately enhancing the crop’s ability to exploit deep water reserves. By combining spatial and temporal monitoring, EMI provides a powerful tool to link soil structural changes to crop water dynamics and resource use efficiency. This work shows how non-invasive geophysical methods can reveal subtle but ecologically meaningful responses in the soil-root continuum under real cropping conditions and supports the potential of bio-drilling to reduce subsoil compaction