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Effects of Liquid‐phase Electrical Conductivity, Water Content, and Surface Conductivity on Bulk Soil Electrical Conductivity
Author(s) -
Rhoades J. D.,
Raats P. A. C.,
Prather R. J.
Publication year - 1976
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1976.03615995004000050017x
Subject(s) - conductivity , electrical resistivity and conductivity , saturation (graph theory) , analytical chemistry (journal) , surface conductivity , water content , electrode , soil water , materials science , capillary action , chemistry , soil science , environmental science , composite material , chromatography , geology , geotechnical engineering , electrical engineering , mathematics , combinatorics , engineering
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.