Document Type



TDR, EM-38, soil electrical conductivity


Electrical conductivity (EC) as measured by the Geonics® EM-38 has shown promise as a soil survey tool. EC is determined by a combination of soluble salts, clay content and mineralogy, water content, and temperature. While investigating use of the EM-38 for soil survey purposes, it is important to understand the relative contribution of each of these variables on EC. A laboratory experiment was set up to determine the relative influence of water content, temperature, and calcite content on EC using time-domain reflectometry (TDR) probes. TDR was used as a proxy for the EM-38 because of the large volume of soil (at least 1 m3) needed to conduct such an experiment with the EM-38. Loess leached of carbonate minerals was air-dried and crushed to pass through a 2-mm sieve to provide a uniform base material. Water and calcite combinations were prepared consisting of five water (air dry, 15, 20, 25, and 30% gravimetric) and four calcite content (0, 10, 20, and 30% by weight) treatments. Bulk EC was determined for each of these combinations at five temperatures (10, 15, 20, 25, and 30°C). Water content accounted for 70 to 78% of the variability in EC when calcite content was held constant and for 70% of the variability across all calcite contents. Multiple regression analysis showed the regression coefficient for water content was at least two orders of magnitude greater than the regression coefficients for calcite content and temperature and up to 79% of the variation in EC could be explained using multiple regression.

Publication Date

September-December 2003

Journal Title

Journal of the Iowa Academy of Science





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© Copyright 2003 by the Iowa Academy of Science, Inc.



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