Determination of cation exchange capacity by one-step soil leaching column method

Abstract

Many methods have been proposed for measuring exchangeable cations and cation exchange capacity (CEC) in soils. Most of these methods are multi-step operations, which are time-consuming and, therefore, not applicable for routine soil tests. Speed and simplicity of operations are necessary. The objective of this study was to develop a one-step soil column leaching method to determine CEC using 0.01 M SrCl₂ solution [CEC(SrCl₂)]. Measured CEC(SrCl₂) values correlate to the conventional CEC [1 M NH₄-acetate (NH₄OAc, pH 7)] in slightly acidic, alkaline, and neutral pH soils. CEC(SrCl₂) was also compared to the effective CEC (ECEC by 0.01 M SrCl₂ and pH 7, 1 M NH₄OAc solutions (soil column leaching method) in red soils. Here, ECEC(SrCl₂) and ECEC(NH₄OAc) are the sum of exchangeable K⁺, Na⁺, Ca²⁺, Mg²⁺, and Al³⁺ in soil column leachates. The correlation between CEC(SrCl₂) versus ECEC(SrCl₂), and CEC(SrCl₂) versus ECEC(NH₄OAc) of seven red soils showed a linear relationship (r² values being 0.99 and 0.98, respectively). The correlation between CEC(SrCl₂) and conventional CEC(NH₄OAc) of five soils (i.e., slightly acidic, alkaline or neutral pH soils) was 0.99. However, a comparison of CEC(SrCl₂) to conventional CEC(NH₄OAc) shows significant differences (p< 0.01) for seven red soils, but not for five other soils (p>0.05). Thus, these results indicate that the advantage of the CEC(SrCl₂) from one-step soil leaching column technique can consider it as ECEC of red soils and CEC of the other slightly acidic, alkaline and neutral pH soils. The one-step soil leaching column method is a rapid, simple technique for determining CEC of most soils and ECEC of red soils.

Keywords:

• Effective cation exchange capacity (ECEC)
• Cation exchange capacity (CEC)

Acknowledgments

This study was supported by the National Science Council, Taiwan, Republic of China, under projects NSC 89-2621-B-002-006 and 89-2621-B-002-019.