Soil electrical conductivity: Effects of soil properties and application to soil salinity appraisal

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Abstract
A model is discussed which relates bulk soil electrical conductivity (ECa) to volumetric water content (θW), electrical conductivity of the soil water (ECW), volumetric content of the solid phase (θS) and average electrical conductivity of the soil particles (ECS). Within the model a distinction is made between the water and dissolved salt present in the “immobile”; (fine pores) and “mobile”; (large pores) phases. The effects of bulk density, particle density and clay content upon ECa are discussed in relation to their influence upon θW, θS, ECS and the proportions of fine and large pores. The practical application of the model to interpret soil salinity requires the estimation of several soil properties in the field and the use of some empirical relations to estimate values of parameters required by the model. These relations and estimates are discussed in terms of their effects on the accuracy of soil salinity appraisal. A brief discussion is given concerning the parameter estimation procedures necessary for the field application of the proposed electrical conductivity model. Evidence is provided to support the utility of the model as an explicit description of electrical conductivity in soil and as a practical field salinity appraisal tool.