A recent study by the Fertilizer and Fertilization Technology Innovation Team at the Institute of Agricultural Resources and Regional Planning (IARRP), part of the Chinese Academy of Agricultural Sciences, has revealed that mixed planting of milk vetch (Astragalus sinicus L.) and ryegrass (Lolium perenne L.) enhances biological nitrogen fixation in paddy fields. Published in the European Journal of Agronomy, the research highlights the role of leguminous green manure in reducing fertilizer use and boosting soil fertility. While the benefits of mixed planting for resource utilization and yield are known, its impact on nitrogen fixation mechanisms was previously unclear.

Through long-term field experiments in Xinyang (Henan province), Jingzhou (Hubei province), and Gao'an (Jiangxi province), combined with ¹⁵N-labeled microplot experiments, researchers assessed the symbiotic nitrogen fixation efficiency of milk vetch and the potential for free-living nitrogen fixation in the soil. The team also analyzed the composition and functional characteristics of nitrogen-fixing microbial communities. 

Results showed that mixed planting of milk vetch and ryegrass significantly increased green manure biomass, soil free-living nitrogen fixation potential, and the symbiotic nitrogen fixation efficiency and total nitrogen fixation of milk vetch, while also enhancing nitrogen uptake by ryegrass. The study further revealed that shifts in the diazotrophic microbial community composition and structure were the key mechanisms through which mixed planting regulated biological nitrogen fixation.

Fan Qianyu, a Ph.D. student at the College of Resources and Environmental Sciences, Nanjing Agricultural University, is the first author. Prof. Cao Weidong from IARRP and Assoc. Prof. Gao Songjuan from Nanjing Agricultural University are co-corresponding authors.

The research was supported by the National Key Laboratory of Efficient Utilization of Northern Arid and Semi-arid Cultivated Land, the National Key R&D Program of China (2021YFD1700200), the National Green Manure Industry Technology System (CARS-22), and the National Natural Science Foundation of China (32472842).

Citation:

Fan Q., Xie J., Du J., Chang D., Liang H., Lv Y., Geng M., Xu C., Hu F., Gao S., Cao W., 2026. Mixed plantation of milk vetch (Astragalus sinicus L.) and ryegrass (Lolium perenne L.) promotes biological nitrogen fixation by modulating diazotrophic community. European Journal of Agronomy, 172, 127880.

Article link: https://doi.org/10.1016/j.eja.2025.127880