Reduced ozone by air filtration consistently improved grain yield in wheat

摘要

This study considered effects of reduced [O_3] on wheat yield. Open-top chamber charcoal filtered air treatments were compared with non-filtered treatments for field-grown wheat. 30 experiments meeting requirements were found, representing nine countries in North America, Europe and Asia. 26 experiments reported improved yield and 4 experiments reduced yield by filtration, a significant positive effect. Average yield improvement was 9%. Average daytime [O_3] was reduced by filtration from 35 to 13 nmol mor~(-1). Filtration efficiency was 63% for O_3 and 56% for SO_2. For NO_x it was observed that NO_2 was reduced and NO increased by filtration. Thus, filters convert NO_2 to NO. Most experiments reported low or very low [SO_2] and [NO_x]. Thus, O_3 can be concluded to be the main phytotoxic component in the experiments. Elevated [NO_2] was observed in one experiment. The conclusion is that current [O_3] over large parts of the world adversely affect wheat yield.