Determination of Effective Cation Exchange Capacity and Exchange Acidity by a One‐Step BaCl 2 Method

Routine laboratory procedures measure effective cation exchange capacity (ECEC) and exchangeable acidity (EA) using separate extractants. This study assessed the suitability of a one‐step BaCl 2 extraction for the analysis of both ECEC and EA on organic and mineral soils by comparing results to those of a multi‐step BaCl 2 extraction already in use by Europe's International Cooperative Programme (ICP)–Forest program. The proposed one‐step BaCl 2 extraction procedure saves time and resources by analyzing both with a single extractant. In both methods, ECEC was calculated by summing base and acid cations, including H + determined by titration, and EA was determined by a second titration of the same BaCl 2 extracts. The effect of the different solution/soil ratios of the one‐step BaCl 2 method was also evaluated. For organic soils, despite the greater solution/soil ratio of the one‐step procedure, the multi‐step procedure extracted more Al and Fe. For mineral soils, increasing the solution/soil ratio of the one‐step method from 10:1 to 20:1 extracted more K, Al, H + , and EA. Adding the rinsing steps of the multi‐step procedure (resulting in a solution/soil ratio of 40:1) not only extracted more of these cations, but also extracted more Ca, Fe, and Mn. The acid cations Al, Fe, and H + were the most significantly affected cations resulting in 30 to 68% more EA and 11 to 41% greater ECEC obtained by the multi‐step procedure. The one‐step BaCl 2 method offers a simpler, more efficient way to analyze these routinely tested parameters.