Abstract:

Straw resource utilization is a key approach for enhancing soil carbon sequestration and regulating nutrient cycling. This study was conducted within a long−term experimental platform for low−carbon agriculture, established by the Shanghai Academy of Agricultural Sciences in 2012. Three straw management practices, including straw removal (CK), direct straw return (SR) and straw biochar return (BC) were compared to assess effects on SOC dynamics in 2024, with particular emphasis on the mineral−associated organic carbon (MAOC) and particulate organic carbon (POC) fractions. The objective was to elucidate the mechanisms through which these practices influence SOC stabilization, providing a scientific basis for enhancing soil carbon sequestration and promoting straw resource utilization. The results showed that: (1) compared with CK treatment, both SR and BC treatments significantly increased SOC content by 25.3% (P<0.05) and 41.4% (P<0.05), respectively, indicating substantial carbon sequestration effects under both straw return practices. (2) Regarding carbon fractions, both SR and BC treatments effectively increased POC content, with increases of 49.1% (P<0.05) and 111.5% (P<0.05) compared to the CK treatment, respectively. Moreover, both straw return practices significantly promoted the formation of MAOC, with increases of 19.7% (P<0.05) and 25.3% (P<0.05) relative to the CK treatment. However, no significant difference was observed between SR and BC treatments in terms of MAOC increase, which may be attributed to competing processes involving microbial activity and homeostasis. In conclusion, straw biochar return not only facilitate rapid carbon sequestration by increasing the POC content, but also enhance long−term carbon sink capacity by promoting MAOC formation. These findings proposed a path toward more sustainable and efficient straw resource management in agricultural systems.

Key words: Straw management, Biochar, Soil carbon fractions, Paddy field, Microbial homeostasis