The air–water interfacial nitrogen cycle produces irrigatable-level ammonium nitrate

, derived entirely from air and water. This carbon-free and catalyst-assisted platform offers a decentralized and environmentally friendly approach to nitrogen fixation, with immediate applications in hydroponic systems, where controlled nutrient delivery is essential. The integration of solar photocatalysis with microdroplet interfacial chemistry establishes a viable foundation for next-generation green fertilizer technologies.