Soil organic carbon (SOC) depletion is a global issue linked to land use changes, climate, and management practices. Poplar plantations (PP), widely grown in the Mediterranean for plywood and bioenergy, have potential for carbon capture, but their impact on SOC and climate change mitigation is understudied. This research evaluated the effect of PP on SOC stocks in arable soils in Northern Italy by analyzing 15 sites across six farms, comparing PP with cropland (CR) and polycyclic plantations (PC). SOC stocks were assessed at 0–10 cm and 10–30 cm depths using a paired comparison and a spatial survey of 30-year-old plantations.

Results showed that PP generally maintains higher SOC stocks than cropland, with significant variations in half of the cases. SOC sequestration rates were 0.09 and 0.32 Mg C ha−1 year−1 for 0–10 cm and 10–30 cm depths, respectively, with a mean rate of 0.75 Mg C ha−1 year−1. Initial carbon loss occurred in the first 1–5 years. PC showed even greater SOC stocks, suggesting its potential for climate change mitigation. The study also identified the need for further research on the effects of fertilization and deep-soil tillage on SOC, along with improvements in supply chain sustainability for PP farmers.