Submitted to: Transactions of the ASAE
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/23/2004
Publication Date: 12/20/2004
Citation: Farahani, H., Buchleiter, G.W., Brodahl, M.K. 2004. Characterization of apparent soil electrical conductivity variability in irrigated sandy and non-saline fields in colorado. Transactions of the ASAE. Interpretive Summary: A soil electrical conductivity (ECa) mapping devise was used to map changes in soil across three center-pivot fields in eastern Colorado from 1998 to 2003. Our objective was to quantify ECa versus soil properties relationships and determine their stability over time. In all three fields, ECa was found to be strongly related to soil water content, clay, and organic matter content. In spite of the strong relationships between ECa and soil properties at each given measurement day, there was no single relationship applicable across all measurement days. Because of that, on-site calibration of ECa versus soil properties of interest are needed at each ECa mapping.
Technical Abstract: Recent advances in apparent soil electrical conductivity (ECa) sensor technology have provided the opportunity to rapidly map the nature of soil spatial variability for site-specific management. Characterizing (or identifying the causes of) the ECa variability, however, has remained difficult with ECa and soil property (such as soil water and clay content) relationships reported in literature showing a wide range of varying strength across fields. Our objective was to quantify the main soil properties that alter ECa and evaluate the temporal variability (or time of measurement dependency) of experimental ECa versus soil properties relationships using multi-year measurements (1998 to 2003) in three center-pivot irrigated sandy and non-saline fields in eastern Colorado. Additionally, we explored the importance of soil properties to explain ECa variability using the theoretically-based dual-pathway ECa model. In all three fields, ECa was found to be a strong linear function of soil water content, clay, cation exchange capacity, and organic matter content with correlation coefficients ranging between 0.75 and 0.9. The empirical linear functions of ECa versus soil properties relationships changed over time when soil solution concentration changed considerably. Because of the lack of reliability of using empirical ECa versus soil properties relationships for predictive purposes over time, on-site calibration of ECa versus soil properties of interest are needed at each ECa mapping.