In-SITE: In situ soil topological examination platform for hydration state, volumetric density and carbon stocks assessment

This study presents a novel application of electrochemical impedance spectroscopy (EIS) for comprehensive soil health assessment, with a particular emphasis on bulk density (BD) analysis. Conventional methods for BD measurement, while effective, can be labor-intensive and prone to inaccuracies, especially in varying field conditions. In contrast, EIS offers a reliable, cost-effective, and non-invasive solution for real-time, in-situ measurements. The research outlines the use of Room Temperature Ionic Liquid (RTIL) functionalized sensors and the development of a portable hardware system for field deployment. Experimental protocols involved collecting impedance data by sweeping from 50 kHz to 5 Hz across various soil types to construct soil moisture profiles, and calibration curves demonstrated a strong correlation between impedance values and soil moisture content, validating the method's accuracy. The study introduces the DENSE model, which uses impedance data to predict soil volumetric density, with results closely matching standard mass/volume techniques. Further analysis reveals the complex relationships between soil moisture, BD, and impedance, producing calibrated models for accurate BD prediction. Additionally, the study extends to carbon stock analysis by integrating data on soil organic carbon percentage, BD, and soil depth to estimate carbon levels. Collectively, these findings underscore the potential of this EIS-based sensor as a versatile and precise tool for real-time soil health monitoring, offering significant contributions to precision agriculture and sustainable farming practices.