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Status of soil electrical conductivity studies by central state researchers

Johnson, C.K., Eigenberg, R.A., Doran, J.W., Wienhold, B.J., Eghball, B., Woodbury, B.L.
Transactions of the ASAE 2005 v.48 no.3 pp. 979
electrical resistance, soil properties, electrical conductivity, electromagnetic induction techniques, Triticum aestivum, winter wheat, grain yield, field experimentation, sensors, precision agriculture, sustained yield management, nitrogen, mineralization, soil fertility, nitrate nitrogen, manure spreading, cattle manure, ammonium nitrogen
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 (EC(a)) 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 EC(a) are highly location and soil specific; soil properties contributing to measured EC(a) must be clearly understood. In soils where EC(a) is driven by NO3-N, EC(a) 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 EC(a) 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 EC(a), EC(a)-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 EC(a) 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 EC(a) as an assessment tool, and the geographic extent to which specific applications of this technology can be applied.