Soil Salinity—Four‐electrode Conductivity Relationships for Soils of the Northern Great Plains

Abstract

Abstract Influence of soil texture, soil geographic location and parent material, and calibration method on the linear EC e ‐EC a relationship was investigated. Linear regression relationships between saturation extract electrical conductivity (EC e ) and bulk soil electrical conductivity (EC a ) as measured by the four‐electrode technique were developed for northern Great Plains soils. Most correlation coefficients (r) exceeded 0.95 and all were significant at the 0.01 probability level. Geographic location had little effect on the EC e vs. EC a relationship; therefore, an EC e vs. EC a calibration made for a soil textural class at one location will apply to another location having a similar range in soil water, clay content, and salinity. Clay content affected linear regression line slopes more than did other factors investigated. Regression slopes varied from 3.06 for a clay to 12.99 for a loamy sand over the clay concentration range of 63.0 to 6.5%, respectively. To minimize adverse effects caused by natural variation in soil texture, water content, and salinity when making field EC e vs. EC a calibrations, we suggest artificial salinization of columns of the soil type in question, which will permit subsequent analysis of the soil by either the cell or EC ‐probe calibration method.