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This article in SSSAJ

  1. Vol. 73 No. 3, p. 737-743
     
    Received: Jan 12, 2008


    * Corresponding author(s): dina.schwertfeger@mail.mcgill.ca
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doi:10.2136/sssaj2008.0009

Determination of Effective Cation Exchange Capacity and Exchange Acidity by a One-Step BaCl2 Method

  1. Dina M. Schwertfeger * and
  2. William H. Hendershot
  1. Dep. of Natural Resource Sci., McGill Univ., MS2-032, 21111 Lakeshore Blvd., Ste. Anne de Bellevue, QC H2X 3V9, Canada

Abstract

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 BaCl2 extraction for the analysis of both ECEC and EA on organic and mineral soils by comparing results to those of a multi-step BaCl2 extraction already in use by Europe's International Cooperative Programme (ICP)–Forest program. The proposed one-step BaCl2 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 BaCl2 extracts. The effect of the different solution/soil ratios of the one-step BaCl2 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 BaCl2 method offers a simpler, more efficient way to analyze these routinely tested parameters.

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