A comparison of salinity measurement methods based on soil saturated pastes

TitleA comparison of salinity measurement methods based on soil saturated pastes
Publication TypeJournal Article
Year of Publication2014
AuthorsAmakor, XN, Jacobson, AR, Cardon, GE, Hawks, A
Pagination32 - 39
KeywordsRepeated measure \{ANOVA\}

Abstract Soil salinization is of great concern in the irrigated arid and semi-arid western U.S. due to its threat to sustainable agricultural productivity and thus is closely monitored. The measurement of electrical conductivity in saturated paste extracts (ECe) is the standard to which other salinity estimation methods are referenced. Since this method is laborious, the preparation of saturated pastes subject to bias, and salinity estimates by electrical conductivity (EC) subject to chemical artifact, numerous other methods have been proposed. These include \{EC\} measurements in diluted saturated paste extracts (ECed), direct measurement of \{EC\} in soil pastes (“Bureau of Soils Cup” method, ECcup), and \{EC\} based on electromagnetic induction (ECH25ECe). The main objective of this paper is to compare these four saturated paste-related methods of estimating salinity with respect to specific soil management goals. Comparison of the methods across six soil depths and three textural groups demonstrates that estimates of salinity are significantly influenced by the method, depth of sampling, and soil texture. Whereas \{ECe\} and \{ECcup\} estimates differed significantly from each other and from those of the other methods, \{ECH25ECe\} and \{ECed\} estimates were similar. In addition, high correlations between estimates of salinity by \{ECH25ECe\} and \{ECe\} indicate their similarity and suggest the suitability of the \{ECH25ECe\} method as a reference parameter for monitoring salinity. Thus, the suitability of the \{ECH25ECe\} method is drawn from its similarity to 1) the superior \{ECed\} method, which corrects for salinity underestimation due to ion pair formation, and 2) the \{ECe\} method, which is the standard method against which other salinity estimates are traditionally compared. This finding was consistent across all depths, the three texture groups, and the combinations of method and depth or texture groups. The high coefficient of variation in \{ECe\} and \{ECcup\} highlights the subjectivity of these methods and raises questions about the choice of \{ECe\} as standard for salinity estimates. These results therefore suggest that the \{ECH25ECe\} method (which requires few collocated but representative \{ECe\} measurements) be used to rapidly and reliably monitor salinity in calcareous soils of arid and semiarid regions.