Pedosphere 36(1): 6--11, 2026
ISSN 1002-0160/CN 32-1315/P
©2026 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Soil organic matter revisited: Why humic substances still matter? |
Sen DOU1 , Yifeng ZHANG1,2, Jun SHAN3, Meng WU3, Rui MA1,4, Song GUAN1, Zhongjun JIA2 |
1 College of Resource and Environmental Science, Jilin Agricultural University, Changchun 130118 (China);
2 State Key Laboratory of Black Soils Conservation and Utilization, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102 (China);
3 State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China);
4 Key Laboratory of Plant Nutrition and Fertilizer in South Region, Ministry of Agriculture, Guangdong Key Laboratory of Nutrient Cycling and Farmland Conservation, Institute of Agricultural Resources and Environment, Guangdong Academy of Agricultural Sciences, Guangzhou 510640 (China) |
| Corresponding Author:Sen DOU |
| ABSTRACT |
| Soil organic matter (SOM) is crucial for ecosystem carbon cycling, soil fertility, and environmental quality. As the main component of SOM, humic substances (HS) are considered a unique category of nonuniformly assembled substances. It is widely accepted that HS are originated from small molecules produced during the decomposition of plant and animal residues or from residual macromolecules. These molecules can be recombined or condensed via enzymatic and mineral catalysis into quasi-macromolecular compounds or compound groups with high condensation (elevated C/H molar ratio) and relatively large molecular weight and are further stabilized by mineral association. Although HS can be regarded as an extension or a narrow definition of SOM, their properties are inherently more complex, and their chemical composition, structure, and formation processes remain controversial. Here, we examine the formation theories, compositional structure, stabilization mechanisms, and functional roles of SOM and HS. We propose that HS indeed differ from non-HS, with HS consisting of both residual and synthetic quasi-macromolecular substance components, which collectively form unique compounds or compound groups with independent characteristics. Consequently, HS remain fundamental to soil science and continue to be widely utilized through various HS-based technologies and products in agriculture and environmental fields. |
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| Citation: Dou S, Zhang Y F, Shan J, Wu M, Ma R, Guan S, Jia Z J. 2026. Soil organic matter revisited: Why humic substances still matter? Pedosphere. 36(1): 6-11. |
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