Estimation of Saturated Soil Paste Salinity From Soil-Water Extracts

Abstract

It is essential to estimate soil salinity with an effective and easy-to-use method. Many laboratories determine soil salinity using a measurement of electrical conductivity (EC) with 1:2.5 or 1:5 soil-water extracts (EC1:2.5, EC1:5) because it is a simpler procedure than the standard saturated paste extract (ECe). Because interpretations of crop tolerance and remediation of salinity are based on values derived from ECe, it is necessary to convert EC1:2.5 or EC1:5 to ECe in order to evaluate plant response and plan management activities. The objectives of this study were to develop and validate models to predict ECe from EC1:2.5 and EC1:5 for important agricultural soils in northern Egypt and to test the transferability of these and similar models developed from other soils. One hundred twenty-six soil samples were collected, of which 105 were used to develop models, and 21 were used to validate the models. Saturated pastes and soil-water extracts were prepared and analyzed for EC. Linear regression models were developed for the two methods. The results demonstrated that ECe was highly correlated (R2 > 0.92, P < 0.001) with EC1:2.5 and EC1:5. An independent validation set of 21 samples showed that the slopes of the regressions between predicted ECe from both EC1:2.5 and EC1:5 measurements and direct ECe measurements were close to 1.0, suggesting that the developed models can reliably assess salinity in soils using either EC1:2.5 or EC1:5 in place of the more expensive and time-consuming saturated paste extraction.