Recently, the Qiyang Red Soil Experimental Station of the Institute of Agricultural Resources and Regional Planning (IARRP) of the Chinese Academy of Agricultural Sciences (CAAS) made significant progress in a study revealing that substituting Chinese milk vetch for chemical nitrogen fertilizer can reduce greenhouse gas emissions, enhance rice yield, and improve nitrogen utilization efficiency. The related findings, titled "Green manure substitution for chemical nitrogen reduces greenhouse gas emissions and enhances yield and nitrogen uptake in rice–rice cropping systems," were published online in Field Crops Research.

In the double-cropping rice regions of southern China, the winter planting and incorporation of Chinese milk vetch into the soil can partially substitute chemical nitrogen fertilizers, thereby reducing the negative impacts of excessive nitrogen application on rice production and the environment. However, the comprehensive analysis of how substituting Chinese milk vetch for different proportions of chemical nitrogen fertilizer affects rice yield, nitrogen uptake, and greenhouse gas emissions. Additionally, the microbial mechanisms underlying these effects are not well understood.. To address this, the study was based on a long-term field experiment initiated in 2008 at the Qiyang Red Soil Experimental Station of the CAAS, investigating the effects of substituting Chinese milk vetch for different proportions of chemical nitrogen fertilizer on rice yield, nitrogen uptake, greenhouse gas emissions, and the microbial mechanisms driving these emissions.

The results of the study indicate that incorporating milk vetch while reducing chemical nitrogen fertilizer by 20% was the optimal strategy for improving nitrogen uptake and rice yield. This treatment promotes conditions conducive to methane-oxidizing bacteria activity, thereby aiding in reducing methane emissions. As a result, the global warming potential of early and late rice was reduced by 44.5% and 39.5%, respectively. This study underscores the critical role of balancing carbon and nitrogen inputs to achieve synergistic improvements in productivity, resource use efficiency, and emission mitigation. It provides robust scientific evidence for advancing clean and sustainable agricultural practices in the double-cropping rice regions of southern China while ensuring food security.

Ph.D. student Nano Alemu Daba and associate researcher Huang Jing from the IARRP are the co-first authors. Researcher Zhang Huimin from the IARRP and Dr. Han Tianfu, associate professor at Zhengzhou University and a former postdoctoral fellow, are the co-corresponding authors. The research was supported by projects including the National Key Laboratory for Efficient Utilization of Dryland and Semi-arid Farmland in Northern China, the National Natural Science Foundation, and the Innovation Project of the CAAS.