Tobacco-rice rotation ensures safe and high-quality rice production in a three-year field experiment

Crop rotation, particularly the paddy-upland system, is a viable strategy to mitigate soil degradation and increased accumulation of hazardous elements under long-term continuous rice monoculture, yet the temporal stability of its benefits on rice quality and heavy metal regulation remains to be fully elucidated. This study conducted a three-year field experiment (2022–2024) across two sites in Southern China to investigate the impacts of a tobacco-rice rotation system compared to continuous rice monoculture. The results demonstrated that the tobacco-rice rotation consistently enhanced rice quality, significantly increasing head rice yield and grain protein content while reducing chalkiness. Although the rotation system resulted in lower soil organic matter and available nitrogen due to high biomass removal, it elevated soil pH and enriched available phosphorus and potassium through legacy fertilization effects in tobacco season. More importantly, the rotation system served as a sustainable strategy for mitigating grain Cd accumulation, increasing the compliance rate with food safety standards from 57.14% to 71.43%. Multivariate analyses further revealed that these improvements were primarily driven by the synergistic effects of the rotation cropping system and the elevated soil pH. These findings confirmed tobacco-rice rotation as a sustainable, long-term agronomic strategy that harmonizes soil health regulation with the rice production with higher quality.