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| Chemical methods to determine soil organic carbon fractions and carbon indexes: A review |
| Received:July 29, 2020 |
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| KeyWord:labile organic carbon fraction;recalcitrant organic carbon fraction;carbon management index;recalcitrant index;soil quality |
| Author Name | Affiliation | E-mail | | ZHANG Fang-fang | College of Resources and Environmental Science, Northwest A&F University, Yangling 712100, China
State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau, Northwest A&F University, Yangling 712100, China | | | YUE Shan-chao | College of Resources and Environmental Science, Northwest A&F University, Yangling 712100, China
State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau, Northwest A&F University, Yangling 712100, China | yueshanchao@nwafu.edu.cn | | LI Shi-qing | College of Resources and Environmental Science, Northwest A&F University, Yangling 712100, China
State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau, Northwest A&F University, Yangling 712100, China | sqli@ms.iswc.ac.cn |
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| Abstract: |
| There are many methods by which to determine the fractions of soil organic carbon, each with specific advantages, disadvantages, and scopes for application. Previous studies were used to comprehensively review the principles, characteristics, and scopes of applying the potassium permanganate, modified Walkley-Black, and acid hydrolysis methods for determining soil organic carbon fractions; these have been used widely in recent years. The advantages and disadvantages of the three methods were emphasized. Improvements in the methods to calculate the carbon management index(CMI)with the development of the organic carbon fraction determination method was described, and the difference in calculating the recalcitrant index(RI) of the recalcitrant soil organic carbon fraction classified by different determination methods was discussed. The citations of the three methods in the recent 19 years(2001-2019)and the citation trend over the recent decade(2010-2019) in CMI and carbon sequestration studies were compared using bibliometric analysis. Given the disadvantages of the three methods and the citation trend in the recent years, the following conclusions can be drawn. First, the potassium permanganate method is suitable for determining the labile soil organic carbon fraction and calculating CMI, and the use of 20 mmol·L-1 potassium permanganate can effectively prevent most of the disadvantages. Second, the modified Walkley-Black method can be used in soil carbon sequestration research and to make weighted calculations of CMI. Third, the acid hydrolysis method can determine the labile and recalcitrant fractions of soil organic carbon when biochemical activity needs to be considered. Finally, the key issues that need further studied in the future includ the direction of methods to determine organic carbon fractions, improving the carbon sequestration potential of soil, and establishing a new carbon pool assessment model. These are needed to provide scientific references to reveal the dynamics in soil quality changes. |
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