Key points are not available for this paper at this time.
Abstract Recent research has demonstrated that field soil salinity can be inferred from four‐electrode soil electrical conductivity (EC a ), if the soil profile is near “field capacity” and calibration curves, based on saturation extract salinity (EC e ), are available. To extend the use of this field method to arbitrary water contents, we studied EC in the laboratory as a function of water content (θ) and in situ soil water conductivity (EC w ). We collected undisturbed cores of four soil types (fsl, vfsl, l, cl) using Lucite column inserts, which were tapped for later insertion of electrodes. The cells were equilibrated with waters of a desired EC w and, using a pressure membrane apparatus, adjusted to a desired θ. Values of EC a were calculated for each EC w − θ equilibration from measured four‐electrode resistances and an appropriate cell constant. Our results indicated that over the θ‐range of practical concern, EC a = (transmission coefficient) × θ × EC w + surface conductivity. This relationship is derived using a simple capillary model, which assumes that liquid phase and surface conductivities (via exchangeable cations) behave as resistors in parallel.
Rhoades et al. (Wed,) studied this question.