The Innovation Team of Fertilizer and Fertilization Technology of the Institute of Agricultural Resources and Regional Planning (IARRP) of the Chinese Academy of Agricultural Sciences (CAAS) uncovered the mechanism by which mixed plantation of different green manure to strengthen the inhibition of cadmium uptake in rice. Their related findings were published under the title "Green manuring reduces cadmium accumulation in rice: Roles of iron plaque and dissolved organic matter" in the international journal "Environmental Research".

Green manuring is not only an important measure to improve rice yield and soil fertility in southern rice fields, but also an effective means to remediate cadmium-contaminated paddy fields in situ and ensure the safe utilization of cadmium-contaminated soil. Mixed plantation of green manure of different genera is a common technique to enhance the effect of green manuring in paddy fields, and whether mixed plantation of different green manure exerts stronger effect on inhibiting cadmium uptake by rice than single plantation is not yet clear.

The study found that compared with winter fallow treatment, green manuring treatments significantly reduced the cadmium content in different tissues of rice. Specifically, the brown rice cadmium content was significantly reduced by 76.6% to 97.0%. The mode of mixed plantation of milk vetch, rape, and ryegrass exerted better effects on reducing Cd uptake by rice than single plantation of milk vetch and rape. Further research indicated that compared with CKl treamnet(without DOM and Fe²⁺), the shoot and root cadmium content in Fe²⁺ and/or DOM (derived from different green manure) treatments significantly reduced by 9.6% to 63.3% and 23.1% to 84.4%, respectively. Moreover, the Fe²⁺ and DOM treatment exerts a better reduction effects, confirming that green manuring inhibits cadmium absorption in rice by increasing the iron plaque content on the rice root surface and promoting the modification of soil dissolved organic matter. These research results can provide technical and theoretical support for the safe production of rice using green manure in cadmium-contaminated paddy fields in southern China.

Master's student Xie Jiancheng from the School of Resources and Environmental Sciences of Nanjing Agricultural University, under the supervision of Professor Cao Weidong from the IARRP, is the first author of this paper. Professor Cao Weidong and Dr. Gao Songjuan of Nanjing Agricultural University are the co-corresponding authors of this paper. This work was financially supported by the National Key Research and Development Program of China (2021YFD1700200), and the earmarked fund for CARS-Green manure (CRAS-22).

Citation: Xie J, Fan Q, Liang T, et al. Green manuring reduces cadmium accumulation in rice: Roles of iron plaque and dissolved organic matter[J]. Environmental Research, 2024, 251: 118719.

Original paper link: https://doi.org/10.1016/j.envres.2024.118719