Electromagnetic Induction Sensing as an Indicator of Productivity on Claypan soils

Claypan soils have a dense, high-clay content layer and cover large areas of the Midwest. Erosion and deposition processes on claypan soil landscapes often determine the depth of the claypan horizon in the soil profile. The claypan may be at or near the surface on eroded sideslopes, yet covered by a significant depth of overwash sediments at lower landscape positions. Productivity is often highly correlated to the thickness of the topsoil (or depth to claypan, DTC) and the physical characteristics of the claypan horizon itself. Variability in these claypan properties must be considered in development of site-specific nutrient management strategies for claypan soils. Standard practice for quantifying claypan depth and characteristics involves using a manual or powered soil probe at each of numerous sampling points, a slow and laborious process. Consequently, mapping of the claypan has not been practical for use in production agriculture decision-making. An automated, preferably noninvasive, measurement technique would be required to quantify claypan variations over a large area. This paper reports on the implementation and evaluation of a commercially available electromagnetic induction (EM) ground conductivity sensor to map claypan soil variability for site-specific nutrient management.