NH3, N2O, NO and NO2 losses, emission factors and reduction mechanisms under different N managements from greenhouse vegetable soils.

Excessive nitrogen (N) application in greenhouse cultivation has led to substantial reactive N (Nr) emissions from soils, necessitating effective mitigation strategies. This study presents simultaneous high-frequency monitoring of ammonia (NH3) volatilization, nitrous oxide (N2O), nitric oxide (NO) and nitrogen dioxide (NO2) emissions across three greenhouse vegetable seasons (tomato, cabbage and lettuce) under different N management regimes. Key findings reveal that emission factors of NH3, N2O, NO, and NO2 were 0.6 %, 1.6 %, 0.8 % and 0.2 % in greenhouse vegetable systems, respectively. Among the emitted annual Nr gases (8.2-72.0 kg N·ha-1), N2O emissions accounted for the highest proportion of total Nr gas losses. Controlled-release N with organic fertilizer emerged as the most effective strategy, significantly reducing total Nr gas emissions while maintaining high vegetable yield. This reduction was mechanistically linked to suppressed urease activity and decreased expression of key microbial genes (amoA, hao, nirK and norB). N application rate, fertilizer type, soil moisture and temperature were identified as the primary drivers of Nr gas emissions. This study firstly provided crucial empirical emission factors and proportions for NH3, N2O, NO and NO2 gases, offering a technical pathway for synergistically reducing pollution and carbon emissions in greenhouse vegetable cultivation.