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 (Nopt) 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 Nopt in NF60; (3) because of higher optimum plant N uptake (PNopt) 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 Nopt model considering O3 pollution in the future.