Impact of ozone pollution on nitrogen fertilization management during maize (Zea mays L.) production

The impacts of ozone (O₃) on crops have been extensively studied and are well understood. However, little information is available on the response of crops (especially maize) to the interactive effects of O₃ and nitrogen (N) fertilizer. To this end, a maize cultivar (Zheng dan 958, ZD958) that is common in China was exposed to two O₃ treatments and four N levels. We found that (1) the interactions between O₃ and N were non-significant for grain yield, plant biomass, C and N, although N addition significantly increased all parameters except C concentrations in grain and plant; (2) compared to NF (non-filtered ambient air O₃ concentration), NF60 (NF plus an extra 60 ppb O₃) increased the optimum N application rates (N_opt) in grain yield and plant biomass, but not grain yield and plant biomass potentials, thus resulting in lower N use efficiencies (NUE) and a larger risk of N-related environmental pollution (e.g., increased N₂O emission) under N_opt in NF60; (3) because of higher optimum plant N uptake (PN_opt) in NF60, relative to NF, plant N-saturated conditions for grain yield potential can be gradually turned into N-limited conditions as O₃ pollution increases. These findings manifest that O₃ is a vital global change factor impacting the management of N fertilization. If current O₃ pollution is substantially reduced, maize yield and biomass potentials can be increased under reductions in N input and N-related environmental pollution. In addition, these results can also contribute in developing and verifying N_opt model considering O₃ pollution in the future.