PARENT SESSION
Monday, August 7, 5:00-6:30 pm
Poster Session 3 - Agroecosystem ecology
Exhibit Hall, Ballroom Level, Cook Convention Center

Farms of the future: soybean productivity and yield in a high- CO₂, high- O₃world.

McConnaughay, K¹, Brewer, E¹, Abts, A¹, Beaver, P¹, Morris, S¹, Morgan, P², Long, S², ¹ Bradley University, Peoria, IL² University of Illinois, Urbana-Champaign, IL

ABSTRACT- Atmospheric CO₂ is predicted to increase from current levels of 375 ppm to 550 ppm by 2050. Atmospheric ozone (O₃) is also increasing. Increases in these atmospheric gases can have profound impacts on the growth and productivity of crop plants: CO₂ through its direct impacts on photosynthesis and plant water use, and O₃ through its direct negative impacts on photosynthesis. Here we report data on effects of increased levels of CO₂ and O₃ on growth and productivity in soybeans from a large-scale, multi-investigator FACE study. We monitored biweekly growth and seed yield for field-grown soybean crops exposed to current and future-predicted atmospheres of CO₂ and/or O₃ for two consecutive years (2004 and 2005). In both years, increased CO₂ availability resulted in increased aboveground net productivity and seed yield. In 2004, a year in which background levels of O₃ were particularly low, soybean growth and seed yield were not affected by ozone levels, with the exception that leaf senescence was accelerated for soybeans exposed to high O₃ and low CO₂. In contrast, in 2005, elevated O₃ reduced soybean productivity and seed yield, but elevated CO₂ ameliorated this response. In addition, soybeans grown at elevated O₃ levels produced smaller seeds. Overall, these results suggest that soybean crops exposed to high levels of O₃ may experience reduced productivity and yield, but that elevated CO₂ may reduce these negative impacts. Similarly, predicted increases in crop productivity and yield due to increased CO₂ availability may be offset by decreases in productivity due to O₃ pollution.

Key words: agriculture yield, elevated carbon dioxide, elevated ozone