Evaluation analysis of the saturated paste method for determining typical coastal saline soil salinity

Abstract

The electrical conductivity of saturated paste extracts (ECe) is more widely used as the laboratory method for estimating soil salinity compared to the soil-water ratio method. However, the current saturated paste process is time consuming and mainly based on subjective experience, and the quantitative relationships among the factors influencing the saturated paste process are not clear. In order to understand and optimize the process of soil salinity determination by saturated paste method, an experiment involving the process of making saturated paste and the key factors in salt determination was carried out on coastal saline silt and sandy loam soils: amount of water added, soaking time, number of centrifugations, and soil particle size. These test factors had clear impact on soil salinity results (both ECe and mass salt content) and pH. Based on the principle of obtaining more mass salt content in this study, suitable parameters for the production of saturated slurries were proposed as follows: (1) the amount of distilled water added to the soil sample should be 2.2 times the saturated water content of the soil; (2) the equilibration time of saturated paste was reduced from 18 to 12 h; (3) only 40 % of the full salt content was obtained by one centrifugation and obtaining 80 % requires three centrifugations; and (4) 0.25–0.50 and 1–2 mm of particle-size sieving should be used to prepare samples of silt and sandy loam soils, respectively.