Use of high-resolution ground conductivity measurements for denitrifying conservation practice placement

Accurate field-scale maps of soil properties including features such as texture, soil organic matter (SOM) content, and hydraulic conductivity are essential for proper placement of conservation practices that utilize anoxic soil environments for denitrification. However, in many cases, soil maps inaccurately represent subsoil properties and can mislead managers about where to install new practices. Non-invasive methods of subsoil property analysis including electromagnetic induction techniques are a potentially efficient method for improving existing field-scale soil maps. In this study, we quantified the accuracy of existing soil maps in an agricultural field in north-central Iowa. Of 60 soil cores collected and reclassified, 19 were identified as taxadjunct at the soil series level primarily due to hydrologic indicators and soil particle size. We assessed the correlation among physical and chemical soil properties measured in-lab and geophysical responses measured in-field. We identified significant correlation of SOM and sand to electrical conductivity for individual core and mean soil series data. From this analysis, we developed a conservation practice suitability map and evaluated the potential for field-scale geophysical investigations to serve as a new tool for agricultural conservation planning and placement of site-specific denitrifying conservation practices. Study results suggest that incorporating a geophysical conductivity investigation into conservation planning may improve understanding of critical soil properties beyond those ascertained with limited soil borings.