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

The impacts of ozone (O) 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 O and nitrogen (N) fertilizer. To this end, a maize cultivar (Zheng dan 958, ZD958) that is common in China was exposed to two O treatments and four N levels. We found that (1) the interactions between O 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 O concentration), NF60 (NF plus an extra 60 ppb O) increased the optimum N application rates (N) 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 NO emission) under N in NF60; (3) because of higher optimum plant N uptake (PN) in NF60, relative to NF, plant N-saturated conditions for grain yield potential can be gradually turned into N-limited conditions as O pollution increases. These findings manifest that O is a vital global change factor impacting the management of N fertilization. If current O 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 model considering O pollution in the future.