Deciphering the nitrogen-promoting effect of vermicompost: from a complex organic matrix to synthetic microbial communities.

Excessive application of chemical nitrogen fertilizers and low utilization efficiency are key issues constraining sustainable agricultural development, and the development of green nitrogen-regulating inputs is a core requirement for the green transformation of agriculture. Vermicompost, produced through the synergistic conversion of organic waste by earthworms and microorganisms, possesses both excellent nitrogen retention capacity and an active microbial community, demonstrating substantial capacity for improving soil nitrogen-use efficiency. Existing research indicates that the combined application of vermicompost and chemical fertilizers can significantly improve crop nitrogen-use efficiency and yield performance. However, there remains a lack of systematic analysis regarding the independent contributions of their matrix and microbial components, as well as the mechanisms underlying their synergistic effects; the pathway from natural microbial resources to the development of precision functional products remains unclear. This review focuses on the central theme of synergy between the substrate and microbial modules, including the overall effects of vermicompost on nitrogen, mechanisms analyzed at the omics level, the mining of functional microbial resources and the design of synthetic microbial communities, as well as field-based targeted regulation and validation of effects, to clarify the core principles of synergistic nitrogen promotion and pathways for technological advancement. We further situate these mechanisms within the broader context of crop root plasticity and plant microbial symbioses, linking vermicompost research to current advances in nutrient acquisition. This review provides a systematic theoretical framework for in-depth research into the mechanisms by which vermicompost promotes nitrogen and for the development of green biofertilizers.