BOOK OF ABSTRACTS 229 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Hall A Poster Session / Environment, Agriculture, and Forestry P4.9 Humic Acid Accumulation and Carbon Stabilization through Cover Crop Incorporation Jeong-Gu Lee1,2*, Chang-Dong Lee1 1 Kyungpook National University, Department of Applied Biosciences, 80 Daehak-ro, Buk-gu, Daegu 41566, Republic of Korea, jeonggu@knu.ac.kr 2 Kyungpook National University, School of Applied Life Science, College of Agriculture and Life Sciences, 80 Daehak-ro, Buk-gu, Daegu 41566, Republic of Korea Soil organic matter is fundamental to soil quality and C sequestration in agricultural systems. Anaerobic conditions influence the stabilization of added organic C by suppressing microbial oxidative activity and promoting the selective preservation of recalcitrant C compounds [1], yet the extent to which cover crop incorporation promotes humic acid formation and stable C accumulation remains unclear. This study evaluated whether green manure derived from a mixture of barley and hairy vetch could enhance humic acid accumulation and C stabilization compared with conventional mineral NPK fertilization. Relative to NPK, green manure (GM) increased CO2 and CH4 emissions, but it also improved soil aggregation [2], as shown by a 21.9% increase in mean weight diameter. GM further increased C concentration within aggregates and elevated hightemperature reactive C in the <0.25 mm aggregate fraction. These results indicate that GM incorporation drove a compositional shift in soil organic matter toward more humified and recalcitrant C forms. Most importantly, both the amount of humic acid and its associated C content were greater in GM than in NPK soil [3]. In conclusion, cover crop incorporation promoted humification and enhanced soil C stabilization through both greater humic acid accumulation and improved aggregate formation. These findings suggest that legumecereal cover crop mixtures represent a practical green manure option for enhancing humification and aggregatemediated C stabilization in paddy soils [4]. References 1. S. Ma, Y. Zhang, D. Beillouin, J. Lu, T. Ren, J. Zhu, Y. Kuzyakov, X. Li, Geoderma 468 (2026) 117762. 2. Y. Chen, L. Huang, S. Huang, T. Guo, S. Zhang, D. Guo, X. Song, S. Ding, M. Mehran, Y. Yang, K. Yue, S. Su, M. Geng, H. Zhang, Soil and Tillage Research 258 (2026) 107024. 3. W. Mi, Y. Sun, Q. Gao, M. Liu, L. Wu, Soil and Tillage Research 195 (2019) 104421. 4. T. Qiu, Y. Shi, J. Peñuelas, J. Liu, Q. Cui, J. Sardans, F. Zhou, L. Xia, W. Yan, S. Zhao, S. Peng, J. Jian, Q. He, W. Zhang, M. Huang, W. Tan, L. Fang, Nature Communications 15 (2024) 10617.
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