Abstract: Optimizing field management practices in agricultural ecosystems can effectively enhance soil organic carbon sequestration, mitigate greenhouse gas emission, and improve soil quality. We examined the effects of chemical fertilizer reduction and biochar application on the components and chemical structure of soil organic carbon (SOC) in a jasmine garden in Fuzhou. There were four treatments in the experiment, including control (CK), reduced chemical fertilizer application (FR), biochar application (BA), and reduced chemical fertilizer application combined with biochar application (FRBA). We measured the content of SOC components and their chemical structure. The results showed that: (1) The FRBA and BA treatments increased recalcitrant organic carbon (ROC) content by 167.1% and 101.3%, and SOC content by 57.8% and 28.2%, respectively (P<0.05). Furthermore, the BA treatment resulted in a 42.6% increase in soil dissolved organic carbon (DOC) (P<0.05). (2) The FR, BA, and FRBA treatments all improved the chemical structural stability and hydrophobicity of soil organic carbon, as indicated by the significant reductions in the relative abundance of o-alkyl carbon (by 76.4%, 69.5%, and 89.4%, respectively) and the significant increases in the relative abundance of phenolic alcohol (by 98.7%, 81.6%, and 114.5%, respectively) (P<0.05). (3) The FRBA treatment significantly increased the aromaticity, lipidization, and total index of soil organic carbon (P<0.05). (4) There were significant correlations between soil organic carbon components, chemical structure, and soil physicochemical properties. Both pH and electrical conductivity were significantly and positively correlated with the contents of SOC, DOC, and ROC (P<0.05). In conclusion, the combined application of reduced chemical fertilizer and biochar increased soil organic carbon pool and enhanced the proportion of stable chemical structural components in SOC. This study provides significant implications for the enhancement of soil organic carbon in jasmine plantations.

Key words: chemical fertilizer reduction, biochar, soil organic carbon component, soil organic carbon structure, jasmine plantation