The objectives of this study were to compare soil chemical properties of gravel fractions (>2 mm) and fine-earth fractions (≦ 2 mm) in a weakly-weathered Regosol derived from basaltic scoria, and to evaluate the relative contributions of these fractions to the chemistry of the whole soil. The gravel fraction was found to contribute to chemical properties of the whole soil as follows: contributions to T-C and Al_0 were 21.3% and 21.4%, respectively; and the contributions to cation exchange capacity (CEC) and each exchangeable cation were 17.4% and 16.7-21.5%, respectively. In the initial stages of formation of Regosols at least over 125 years, it is evident that most soil chemical properties are associated with the fineearth fraction. However, some organic carbon and available nutrients also accumulated concomitantly in gravel fractions. In order to evaluate the chemical properties of Regosols derived from basaltic scoria, which is a porous parent material, it is necessary to recognize that the gravel fraction as well as the fine-earth fraction contributes to the whole-soil properties.
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