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.
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.