Soil salinity using saturated paste and 1:1 soil to water extracts

Saturated paste (SP) and 1:1 soillwater extractions (1:1) are commonly used to assess soil salinity for field remediation. Correlation of electrical conductivity (EC) and other analytes between the SP and 1:1 extraction methods have been documented, except the relationships were based on limited soil types and require further examination to be adequately evaluated. This study examined these relationships using 170 soils from petroleum and agriculture production sites. Saturated pastes and 1:1 extracts were prepared and analyzed for EC, major cations (Na+, K+, Mg2+, Ca2+), and major anions (Cl-, SO42-). Relationships of all analytes were established between the two methods using linear regression. Saturated paste extract EC (ECSP) was highly correlated with that of 1:1 extract EC (EC1:1) (r(2) = 0.85, P < 0.001). Significant relationships also existed (r(2) > 0.73, P < 0.001) between different ions in SP and 1:1 extracts. An independent validation set of 22 soils showed that the slopes of the regressions between predicted EC, Na+, and Cl- of SP equivalents from 1:1 extract measurements and direct SP extract measurements were very close to 1.0 suggesting that the regressions developed can accurately assess soil salinity in salt affected soils using 1:1 extract analysis instead of using the more expensive and time-consuming SP extraction.