ELECTRICAL-CONDUCTIVITY METHODS FOR MEASURING AND MAPPING SOIL-SALINITY

This chapter reviews the various electrical conductivity methods for measuring soil salinity together with compatible ways for mapping it, including establishing the locations of measurement sites. Advantages and limitations of the alternative methods are discussed and a practical integrated mobile system for measurement/monitoring/mapping is described. Measurement of the electrical conductivity of saturated soil paste extracts can be accurately predicted from measurements of the electrical conductivity and saturation percentage of the soil paste, with substantial savings in time. The measurement of bulk soil electrical conductivity (EC made using both four-electrode and electromagnetic induction techniques, can be used to even greater advantage for salinity appraisal. Soil salinity can be determined from EC, directly in the field without requiring laboratory analysis. Alternatively, limited ground-truth techniques involving limited laboratory analysis can be used to predict salinity from the more easily and quickly made measurements of EC,. Both of these salinity assessment techniques have been shown to be reliable and practical. Commercial instrumentation is available for measuring EC, using both four-electrode and electromagnetic induction methodology. These equipment and methodologies have been shown to be useful for purposes of measuring, monitoring, and mapping field salinity, for detecting the presence of shallow water tables, and for assessing the adequacies of leaching and drainage practices for soil salinity control. © 1993, Academic Press Inc.