The fertilizer and fertilization technology innovation team at the Institute of Agricultural Resources and Regional Planning (IARRP), Chinese Academy of Agricultural Sciences, recently reported that combining green manure (Chinese milk vetch) and rice straw with rapeseed-straw biochar can synergistically reduce cadmium (Cd) bioavailability, improve soil fertility and increase rice yield. These findings were published in the Journal of Hazardous Materials (CAS Zone 1, top journal) under the title A comprehensive strategy for solving Cd risk while improving soil quality and rice yield in paddy fields: Co-utilizing green manure, rice straw, and biochar.

Cd contamination in farmland soils is a global challenge. Existing remediation measures mostly rely on external inputs and often neglect the soil's intrinsic regulatory capacity. Identifying approaches that simultaneously enhance soil quality and mitigate Cd risk are urgently needed. Returning Chinese milk vetch and rice straw to the field maintains paddy productivity, while biochar is widely used to immobilize Cd. Rapeseed-straw biochar has shown promising Cd-control potential in milk vetch–rice straw co-incorporation systems, but its long-term effects and underlying mechanisms are not fully understood.

Through field plot experiments, pot trials and laboratory simulations— using XRD, FTIR, XPS and random forest analysis—the team systematically investigated the mechanisms governing Cd immobilization under the combined amendment strategy. Results confirmed that co-utilizing milk vetch, rice straw and biochar effectively achieves "Cd-reduction, soil quality-improvement and rice yield-increase" goals in southern paddy fields. This model not only produced the highest soil quality index and sustained yield gains during the study period, but also significantly reduced soil available Cd and Cd content in brown rice.

Mechanistically, dissolved organic matter derived from milk vetch and rice straw optimized the surface properties of biochar—enhancing negative charge, specific surface area and oxygen-containing functional groups—thereby improving Cd²⁺ adsorption capacity. Meanwhile, dissolved organic matter and biochar jointly strengthened the rice antioxidant defense system and regulated the expression of Cd-related transporter genes, reducing Cd uptake and translocation.

This research provides a feasible technical pathway for integrated soil fertility improvement, grain yield enhancement and Cd-pollution control in southern rice-growing regions.

The paper's co-first authors are Dr. Liang Ting and Assistant Researcher Chang Danna. Researcher Cao Weidong serves as the corresponding author. The work was supported by the State Key Laboratory of Efficient Utilization of Arid-Region Dryland Farmland, the National Key R&D Program (2021YFD1700200), the National Green Manure Industry Technology System (CARS-22), and the Agricultural Science and Technology Innovation Program of CAAS.

Citation:

Liang, T., Chang, D., Zhou, G., et al. (2025). A comprehensive strategy for solving Cd risk while improving soil quality and rice yield in paddy fields: Co-utilizing green manure, rice straw, and biochar. Journal of Hazardous Materials, 500, 140372.

Article link：https://doi.org/10.1016/j.jhazmat.2025.140372.