Well-facilitated Farmland Construction enhances soil organic carbon storage in China

Soil organic carbon (SOC) is central to regulating the global carbon cycle and underpinning food security, yet unsustainable cultivation has resulted in a continuing SOC loss and has made it highly vulnerable to climate change. In China, the Well-Facilitated Farmland Construction (WFC) initiative has sought to enhance soil conditions by integrating farmland management units (FMUs) and adopting improved practices, including optimized irrigation, straw incorporation, and targeted fertilization strategies. Since its launch in 2013, the WFC project has been implemented across more than 50 million hectares of farmland in China. However, its spatio-temporal impacts on SOC remain poorly understood. To address this gap, we focused on three representative regions, Shunyi, Rudong, and Dangtu, to examine the impact of FMU integration. A total of 1,549 soil profiles were compiled to calibrate the process-based CENTURY model and simulate long-term variations in topsoil (0-20 cm) SOC density (SOCD) across Chinese farmlands. Results show that, following the WFC project, farmland fragmentation decreased while SOCD increased, with strong negative correlations between fragmentation degree and SOCD (-0.88 in Shunyi, -0.94 in Rudong, and -0.52 in Dangtu). These findings indicate that farmland patch integration contributes significantly to SOC sequestration. By comparing future SOC trajectories under traditional versus WFC practices, we found that WFC management offers substantial sequestration potential, increasing SOC stocks by 3.34 Pg under SSP1-2.6 and 2.86 Pg under SSP5-8.5 during 2030-2100 in Chinese farmlands. This sustained increase reflects the synergistic effects of fertilization and elevated CO₂, enhanced crop productivity through optimized irrigation, greater organic inputs from straw incorporation, and reduced microbial decomposition under balanced nitrogen fertilization. In conclusion, WFC demonstrates a scalable pathway toward more resilient and climate-smart food systems.