Enhanced reactive oxygen species generation potential in long-term fertilized soil mitigates microbial carbon and phosphorus co-limitation

Reactive oxygen species (ROS) are ubiquitous in soil, yet their generation in managed ecosystems and roles in microbial resource acquisition remain unknown. Based on a survey in a 31-year long-term fertilization field, we report that mineral NPK fertilization, alone or combined with cattle manure, increases the O 2 ⋅− and ⋅ OH contents by 0.5–2.7 and 1–3.7 times, respectively. This increase is driven by the enhanced abundance of Fe(II) and specific Proteobacteria and Firmicutes members, facilitating redox reactions for ROS generation. Integrating incubation experiments, we find that the resulting ROS could mitigate microbial C and P co-limitation through interacting non-enzymatic and enzymatic pathways. O 2 ⋅− and ⋅ OH mobilize dissolved organic carbon (DOC) and Olsen-P through Fe(III)-bound C/P decomposition and recalcitrant organics degradation. Crucially, O 2 ⋅− stimulates enzyme activities by providing substrates and cleaving inhibitory adducts. These findings reveal the ROS generation mechanism in fertilized soils and highlight their overlooked positive role in nutrient cycling.