Ozone treatment enhances yield and quality of soilless-grown lettuce by modulating bacterial communities in the nutrient solution

Recirculating hydroponic systems enhance water-fertilizer use efficiency in greenhouse production but are susceptible to pathogen accumulation and microbial imbalances over prolonged operation. Ozone represents a promising eco-friendly disinfection method; however, its ecological effects on nutrient solution microbiomes and crop performance remain poorly understood. This study evaluated the impact of four ozone concentrations (0, 1, 2, and 4 mg L –1 ) on microbial community composition and lettuce production in greenhouses. High-throughput sequencing and multivariate analyses were employed to explore dose-response relationships between ozone levels, lettuce growth, and microbiome dynamics. Low ozone concentrations (1–2 mg L –1 ) significantly improved lettuce yield, quality, and water-fertilizer use efficiency, while 4 mg L –1 exhibited inhibitory effects. Ozone treatment reduced bacterial richness and diversity, with the most pronounced effect occurring at mid-growth (day 20). Proteobacteria dominated the microbial communities, and Pseudomonas abundance decreased with increasing ozone concentration. Functional predictions revealed possible shifts in chemoheterotrophic groups and nitrogen-cycling-related taxa. Random forest analysis highlighted Flavihumibacter, Runella , and Cytophaga as key taxa correlated with yield and quality (R 2 = 0.595–0.938). Partial least squares path modeling suggested that ozone-induced microbial restructuring influenced variations in lettuce growth. These findings provide mechanistic insights into ozone-driven microbiome modulation and offer practical recommendations for optimizing ozone management in recirculating nutrient solution systems for soilless cultivation, promoting the sustainable application of controlled-environment agriculture under realistic conditions.