Influence of Water Content on Electrical Conductivity of the Soil

Abstract Measurement of dynamic salinity and water content profiles under laboratory conditions were needed to test a model developed to characterize the simultaneous flow of water and salts in soils. Methods were needed for measuring salinity in place in a system where rapid water movement occurred. Because of the time lag in salinity sensors, other methods were considered for evaluating salinity. The four‐probe system of measuring electrical conductivity of soil eliminates the time lag error, but introduces the problem of correcting the changes in conductivity caused by water content. Units were constructed and samples prepared to evaluate the influence of water content, and salt concentrations on the four‐probe conductivity (K4P). Two soils were studied. Regression equations developed to estimate saturation or 1:5 extract electrical conductivity from four‐probe conductivity and water content (π) gave correlation coefficients of 0.75 and 0.90, respectively. Correlations for individual soils were generally higher than the combined soils. The regression equation relating the ratio of K 4 P to four‐probe conductivity at saturation ( K 4 PS ) with water content was 4 K 4 P / K 4 PS = − 0.26 + 2.49π with a correlation coefficient of 0.88 for the combined soil data.