Author(s)

Xiangzheng Kong^1,2, Decheng Li^1*, Xiaodong Song¹, Ganlin Zhang¹

¹State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, China.
²University of Chinese Academy of Sciences, Beijing, China.

The removal of organic matter and iron oxides could increase and decrease soil CEC in tropical and subtropical regions, but the quantitative information is insufficient so far about the change of soil CEC, the influence factors and their contribution. In this study, the subhorizon soils of 24 soil series in the tropical and subtropical China were used, pH, particle size composition, organic matter, iron oxides of these samples were measured, and also CECs were measured and compared for the original soils and after the removal of organic matter and iron oxides. The results showed that, compared with CEC of the original soil, the eliminating organic matter increased soil CEC significantly by 2.28% - 56.50% with a mean of 24.02%, but the further obliterating iron oxides decreased soil CEC significantly by 0.75% - 20.30% with a mean of 7.73%. CEC after the removal of organic matter and iron oxides had positive correlation with iron oxides (p < 0.01) and negative correlation with sand content (p < 0.01 and p < 0.05). CEC after organic matter eliminated was mainly decided by iron oxides (51.68%), followed by silt content (22.19%); while CEC after iron oxides obliterated was mainly determined by iron oxides (50.55%). The increase of CEC after organic matter eliminated was co-affected by the contents of clays, slits, iron oxides and pH (22.00% - 27.34%), while the decrease of CEC after iron oxides obliterated further was dominated by the content of organic matter (66.92%). More other soil parameters should be considered for higher predicting accuracy in the regression model of soil CEC after the removal of organic matter and iron oxides, and the recommended optimal models obtained in this study were as follows: for soil CEC after organic matter eliminated, CEC = 1.665 − 0.546pH − 0.024OM + 0.053Fe_xO_y − 0.001Silt + 0.007Clay + 0.972CEC_original (R² was 0.923, RSME was 1.55 cmol(+)∙kg⁻¹, p < 0.01), while for soil CEC after iron oxides further obliterated, CEC = 1.665 − 0.546pH − 0.024OM + 0.053Fe_xO_y − 0.001Silt + 0.007Clay + 0.972CEC_original (R² was 0.923, RMSE was 1.55 cmol(+)∙kg⁻¹, p < 0.01). Further research is needed in the future as for exploring internal functional mechanism in view of soil electrochemistry and mineralogy.

Soil CEC, Quantitative Estimation, Removal, Organic Matter, Iron Oxides

Kong, X. , Li, D. , Song, X. and Zhang, G. (2021) Quantitative Estimation of the Changes in Soil CEC after the Removal of Organic Matter and Iron Oxides. Agricultural Sciences, 12, 1244-1254. doi: 10.4236/as.2021.1211079.