Annual NO and N

Context Overuse of N fertiliser in vegetable cropping systems is known to release of nitric and nitrous oxide to the atmosphere in China. Optimisation of N fertilisation regimes has the potential to mitigate NO and N2O emissions from these N-rich systems. Aims We investigated the effects of different N fertilisation regimes on NO and N2O emissions, and vegetable yields, with particular efforts to estimate annual direct emission factors of NO and N2O under different N fertilisation regimes in greenhouse vegetable fields. Methods Annual NO and N2O fluxes were taken simultaneously using the static chamber-based method from a greenhouse vegetable system in south-east China with four N fertiliser treatments: (1) no N fertiliser (control); (2) chemical N fertiliser application (CF); (3) organic N fertiliser application (OF); and (4) organic-chemical mixed N fertiliser application (MF). Key results N fertilisers significantly increased NO and N2O emissions. Direct emission factors of N fertiliser for NO and N2O were the largest for MF, with an average of 0.99% and 0.67%, respectively. Vegetable yields were only significantly enhanced under OF treatment. Conclusions Relative to the use of chemical N fertiliser, the application of organic-chemical mixed N fertiliser showed not to be effective for mitigating NO and N2O emissions. Instead, sole application of organic N fertiliser was a viable option to enhance vegetable yields but without increasing NO and N2O emissions in greenhouse vegetable systems. Implications Substituting the use of chemical N fertiliser with organic N fertiliser input could benefitvegetable production but without stimulating NO and N2O emissions from vegetable cropping systems in sub-tropical China.