Use of the corrected clay CEC value for oxisols identification
2000
Wiharso, D. (Universitas Lampung, Bandar Lampung (Indonesia). Fakultas Pertanian)
Soil taxonomy has been planned to be a global soil classification system, however it is not comprehensive enough to cover all soil problems in the world, especially in tropical region where soil weathering process are fairly fast. Limited information of soil genesis on tropical region resulted in some unsolved tropical soil classification. In highly weathered soils, the value uncorrected Clay CEC by organic matter is not stable, since the CEC is highly affected by the soil organic matter content. The objective of this research were to study the distribution of corrected Clay CEC value in highly weathered soils solum and to use the value for Oxisols identification. To pursue these objectives, four soil properties of soil profiles reported by Soil and Agroclimate Research Institute in Bogor were evaluated. The soil properties evaluated included soil texture, weatherable minerals, organic carbon, and CEC. The Clay CEC was corrected by substracting CEC of organic matter which was 4 cmol (+) kg/10. The results showed the variability of uncorrected Clay CEC values in soil profiles which were depended on the organic matter content, while the distribution of corrected Clay CEC values showed homogenous in soil profiles; changes in organic matter content especially in subsurface horizon, either naturally or by man activities changed the Clay CEC value; therefore, it may change the soil taxa in high category; the corrected Clay CEC values indicated high correlation with the value of weatherable minerals. Therefore the corrected Clay CEC value is better to be used to classify highly weathered soils in tropical region than the uncorrected Clay CEC value, and the corrected Clay CEC value on soil surface horizon can be used to identify Oxisols if there is no clay skin in the diagnostic horizon
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