A Method for Measuring Soil Solution Electrical Conductivity in the Field Using TDR

Abstract

This paper describes a simple and easy method for estimating soil solution electrical conductivity (ECw) and electrical conductivity of saturation extracts (ECe) in the field from simultaneous measurements of volumetric water content (θ) and bulk soil electrical conductivity (ECa) made using TDR. A model that relates ECw to θ and ECa (Rhoades et al., 1976) and the EC of an aqueous extract from a soil paste of 1:1 soil-water ratio (EC1:1) form the basis of this method. The relationship of EC1:1 to the EC of the soil solution of the same soil of 1:x soil-water ratio (EC1:x) is assumed to be EC1:x=x-nEC1:1 where n is a parameter to be determined by experiment but is assumed to be one in this study. The parameters of Rhoades' model are determined based on the ECw estimated from the EC1:1 using the relationship assumed above. This method was applied to two irrigation experiments conducted in an irrigated cornfield in a semiarid region, China and in a grass-covered spot in a humid region, Japan. The results show that this method is effective in monitoring soil salinity in the field.