This paper describes a simple and easy method for estimating soil solution electrical conductivity (EC_w) and electrical conductivity of saturation extracts (EC_e) in the field from simultaneous measurements of volumetric water content (θ) and bulk soil electrical conductivity (EC_a) made using TDR.
A model that relates EC_w to θ and EC_a (Rhoades et al., 1976) and the EC of an aqueous extract from a soil paste of 1:1 soil-water ratio (EC_1:1) form the basis of this method. The relationship of EC_1:1 to the EC of the soil solution of the same soil of 1:x soil-water ratio (EC_1:x) is assumed to be
EC_1:x=x^-nEC_1:1
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 EC_w estimated from the EC_1:1 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.