Relating Sodium Percentage to Sodium Adsorption Ratio and its Utility in the Northern Great Plains

Saturated paste derived sodium adsorption ratio (SARe) is not a routine procedure for soil testing laboratories in the northern Great Plains. The objective of this study was to determine the relationship between SARe, a solution-phase only extraction, and percentage of Na (% Na; Na/(Na+Ca+Mg+K), a solution phase plus exchange phase value using 1M ammonium acetate as an extractant. From the analysis of 1974 soil samples from the northern Great Plains, simple-linear and quadratic regressions were highly significant at predicting SARe from % Na data. Removal of outliers only slightly increased r(2) values for both models. We found that using % Na from a routine soil test is acceptable for assessment of soil Na levels to help make soil management decisions.