Long-term Effectiveness of Cadmium-Stabilizing Materials: Machine Learning and Meta-Analysis Confirm the Sustained Efficacy of Biochar in Soil-Rice Systems

Based on the results of long‑term experiments with existing immobilization materials, this study identifies the material type that exhibits the most durable and stable performance and explores the key soil physicochemical properties and material characteristics that govern its long‑term immobilization effectiveness. By systematically collecting published data from long‑term studies on immobilization materials and conducting subgroup analyses and calculating the effect size lnRR in Meta‑Win, the results indicate that biochar is the most effective long‑term immobilization material. The study found that the optimal range of soil physicochemical properties for biochar gradually narrows from the long term to the medium term, suggesting that soil organic matter (SOM), clay content, and cation exchange capacity (CEC) play important regulatory roles in stabilizing biochar’s long‑term performance. Further analysis of biochar’s intrinsic properties revealed that its immobilization effectiveness primarily depends on pyrolysis temperature, inherent pH, and application rate.