Assessment of Saturated Soil Paste Salinity from 1:2.5 and 1:5 Soil-Water Extracts for Coarse Textured Soils

It is important to determine soil salinity with an accurate and simple method. Electrical conductivity (EC) of soil-water extracts is commonly used to assess soil salinity because it is an easier method than the standard saturated paste extract (ECe). However, it is essential to convert EC of soil- water extracts to ECe because plant response and salinity remediation are based mainly on ECe values. Our objectives were to develop and validate models to predict ECe from EC of 1:2.5 and 1:5 soil-water extracts (EC1:2.5, EC1:5). One hundred thirty-six coarse textured soil samples were collected from El Beheira Governorate, Egypt, of which 115 were used to develop models and 21 were used to validate these models. Electrical conductivity was determined using 1:2.5 and 1:5 soil-water extracts and saturated paste extracts (ECe). Linear regression models were established for the two methods. The results showed that ECe was highly significant correlated (R^2 = 0.96 to 0.97, P 0.001) with EC1:2.5 and EC1:5 for ECe values ranging between 0.3 and 18.3 dS m^-1. An independent validation set of 21 soil samples showed that the R2 and slopes of the regressions between predicted ECe from both EC1:2.5 and EC1:5 values and direct ECe values were very close to 1.0. Additionally, these new models reduced ECe prediction errors by 2.4 to 7 times when compare with 8 predictive models reported in the literature. Confirming that the regressions developed can reliably assess soil salinity instead of the more time-consuming and expensive saturated paste extraction.