STATUS OF SOIL ELECTRICAL CONDUCTIVITY STUDIES BY CENTRAL STATE RESEARCHERS

Practical tools are needed to identify and advance sustainable management practices to optimize economic return, conserve soil, and minimize negative off-site environmental effects. The objective of this article is to review current research in non-saline soils of the central U.S. to consider bulk soil electrical conductivity (ECa) as an assessment tool for: (1) tracking N dynamics, (2) identifying management zones, (3) monitoring soil quality trends, and (4) designing and evaluating field-scale experiments. The interpretation and utility of ECa are highly location and soil specific; soil properties contributing to measured ECa must be clearly understood. In soils where ECa is driven by NO3-N, ECa has been used to track spatial and temporal variations in crop-available N (manure, compost, commercial fertilizer, and cover crop treatments) and rapidly assess N mineralization early in the growing season to calculate fertilizer rates for site-specific management (SSM). Selection of appropriate ECa sensors (direct contact, electromagnetic induction, or time domain reflectometry) may improve sensitivity to N fluctuations at specific soil depths. In a dryland cropping system where clay content dominates measured ECa, ECa -based management zones delineated soil productivity characteristics and crop yields. These results provided a framework effective for SSM, monitoring management-induced trends in soil quality, and appraising and statistically evaluating field-scale experiments. Use of ECa may foster a large-scale systems approach to research that encourages farmer involvement. Additional research is needed to investigate the interactive effects of soil, weather, and management on ECa as an assessment tool, and the geographic extent to which specific applications of this technology can be applied