Development of an equation to relate electrical conductivity to soil and water salinity in a Mediterranean agricultural environment

A linear equation to relate total ionic concentration to electrical conductivity (EC) in natural aqueous systems from low to medium level salt content was derived from the theory of EC in aqueous solutions. Some of the empirical equations used in soil science to characterise the salinity of soil and water based on the EC can be reduced to that equation. Also, it can be seen that aqueous systems with different relative ionic compositions have different values for the regression coefficient that relates EC to total ionic concentration. The equation was validated on the basis of the Faraday constant with some soil saturation extracts and irrigation waters sampled in different places along the Valencian Community (eastern Spain, western Mediterranean basin), and with data from the literature. The validation was performed using the chemical speciation program SOILSOLN. The results of the validation improved when activities were considered instead of concentrations, and in more dilute aqueous systems. Finally, the validation showed that the formation of ion pairs in the aqueous systems analysed was negligible due to the relatively low concentrations of sulfate, magnesium, and calcium. Keywords: chemical speciation, Faraday' s constant, ionic mobility. Australian Journal of Soil Research 42(4) 381 - 388 Full text doi:10.1071/SR03155 © CSIRO 2004