Effects of Liquid‐phase Electrical Conductivity, Water Content, and Surface Conductivity on Bulk Soil Electrical Conductivity

Abstract

Recent research has demonstrated that field soil salinity can be inferred from four‐electrode soil electrical conductivity (ECa), if the soil profile is near “field capacity” and calibration curves, based on saturation extract salinity (ECe), 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 (ECw). 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 ECw and, using a pressure membrane apparatus, adjusted to a desired θ. Values of ECa were calculated for each ECw − θ equilibration from measured four‐electrode resistances and an appropriate cell constant. Our results indicated that over the θ‐range of practical concern, ECa = (transmission coefficient) × θ × ECw + 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.

Correlación Espacial Entre Malas Hierbas en Una Pradera Y Su Relación Con La Conductividad Eléctrica Aparente Del Suelo (Ce a )

“…Según Lesch et al (2000), Lesch (2005), Rhoades et al (1976) y McNeill (1980 la conductividad eléctrica aparente del suelo ha sido bastante utilizada en los últimos años ya que tiene una fuerte relación con diferentes propiedades del suelo, como: porosidad, concentración de electrólitos disueltos, textura, cantidad y composición de los coloides (arcilla y materia orgánica), contenido de materia orgánica y contenido de agua en el solo.…”

Metrological assessment of TDR performance for measurement of potassium concentration in soil solution

“…Models developed by Rhoades et al (1976) and Muñoz-Carpena et al (2005) were used to estimate the electrical conductivity of the soil solution (CEw). These models were fitted by minimizing the sum of square error between CEw measured with an electrical conductivity meter (Digimed DM-32) and estimated with TDR (probe characteristics: three rods, 0.1 m long, 0.03 m rod diameter, 0.017 m spaced root length sensors), in a sandy-clay (Sc) and loamy-sand (Sf).…”

“…Over the years, several mathematical models (empirical or physical) were developed to relate ECa and θ, in order to determine the electrical conductivity of the soil solution, CEw, from the soil water content and soil apparent electrical conductivity (Rhoades et al, 1976;Vogeler et al, 1996;Muñoz-Carpena et al, 2005) among others. Out of these models emerged a new application for the technique; the real time monitoring of the ionic composition of the soil solution.…”

Potassium estimation in the soil solution based on electrical conductivity and soil water content

“…The soil solution may be an alternative for obtaining nutrient levels by laboratory analysis or by using kits for fast determination of levelsof these nutrients. Nutrient levels in soil solution may also be estimated by models from bulk electrical conductivity (ECw) or soil solution electrical conductivity (ECss) (Rhoades et al, 1976;Vogeler & Clotheir, 1996;Muñoz-Carpena et al, 2001;Santana et al, 2007).…”