Assuming gradual rises in ozone levels, the findings suggest that the U.S. soybean industry may suffer an additional $21 million loss each year for the next 30 years. However, researchers say, rising carbon dioxide levels may reduce some ozone effects, but other global warming factors cloud their ability to get a clear view of the future.
Findings of a study done in the 2002 growing season were presented today by Patrick B. Morgan, an Illinois doctoral student in the department of plant biology, at Plant Biology 2003, the annual meeting of the American Society of Plant Biologists, in Hawaii. Morgan's work was specially selected by the society for presentation.
Ozone levels in industrialized nations have been rising annually by 0.5 percent to 2.5 percent, with the highest levels occurring in the northern hemisphere. At Illinois, researchers from around the world are conducting the only open-air experiments, exposing crops to anticipated future levels of ozone and carbon dioxide.
Soybean losses begin at ozone concentrations of 40 parts per billion. In Illinois, the average concentration is already 64 parts per billion with occasional daily spikes as high as 120 parts per billion, Morgan said. In his study, experimental soybeans, a cultivar commonly grown in the Midwest, were exposed to an average concentration of 75 parts per billion (coinciding with a 20 percent increase projected by the Intergovernmental Panel on Climate Change), while the average for control soybeans was 62 parts per billion.
Illinois researchers found that soybeans suffer significant losses in leaf photosynthesis as leaves age and, more dramatically, in overall biomass.