Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/18/2005
Publication Date: 7/1/2005
Citation: Johnson, C.K., Eigenberg, R.A., Doran, J.W., Wienhold, B.J., Eghball, B., Woodbury, B.L. 2005. Status of soil electrical conductivity studies by central state researchers. Transactions of the ASAE 48(3):979-989. Interpretive Summary: Practical tools are needed to identify and advance sustainable agricultural management practices. This includes economic return, soil conservation, and environmental issues. Current research in the central U.S. was reviewed to consider the use of soil electrical conductivity to evaluate soil properties. Soil conductivity can be used to detect changes in soil nitrogen. It can also detect changes in nitrogen available to crops resulting from farming practices. Conductivity has the potential to quickly measure naturally occurring nitrate production. This is important early in the growing season to calculate fertilizer needs for site-specific management. Selection of appropriate conductivity sensors can improve performance of the tool. In a dryland cropping system, soil conductivity identified patterns of soil properties and crop yields. However, in a sandy soil no correlation was found between soil conductivity and nitrate levels. While use of soil conductivity may encourage farmer acceptance of sustainable management practices, some caution is needed in interpretation. Additional research is needed to investigate how the effects of soil, weather, and management can be interpreted when using soil conductivity
Technical Abstract: Practical tools are needed to identify and advance sustainable management practices to optimize economic return, conserve soil, and minimize negative environmental effects. Current research in the central U.S. was reviewed to consider the utility of bulk soil electrical conductivity (EC) as an assessment tool. Measured EC can be used to track N dynamics in soil. It can detect variations in crop-available N due to manure, compost, commercial fertilizer, and winter cover crop treatments. Selection of appropriate EC sensors (direct contact, electromagnetic induction, or time domain reflectometry) can improve sensitivity to N fluctuations at specific soil depths. Surveyed EC has the potential to rapidly assess N mineralization early in the growing season, information essential for calculating fertilizer rates for site-specific management (SSM). Yet, in a sandy loam soil no correlation was found between EC (0 to 75 cm) and soil inorganic N (0 to 30 cm), indicating that care must be taken when interpreting EC. In a dryland cropping system, EC-based management zones delineated soil characteristics and crop yields to provide a framework for SSM, and for appraising and statistically evaluating field-scale experiments. Clearly, use of EC fosters a large-scale systems approach to experimentation that addresses many sustainability issues. This approach may also encourage farmer involvement and acceptance of sustainable management practices. Yet, EC interpretation is highly location and soil specific. Additional research is needed to investigate the interactive effects of soil, weather, and management on EC and the geographic extent to which specific applications of this technology can be applied.