Impact of ozone and sulphur dioxide on soybean yield

Little dose-response information exists on the effects of chronic ozone (O₃) and intermittent sulphur dioxide (SO₂) exposures on the yield of important agricultural crops. Such information is needed for the refinement of estimates of air pollution-induced crop losses. Field-grown plants of two soybean cultivars (Glycine max L. Merr, ‘Amsoy-71’ and ‘Corsoy-79’) were exposed to incremental chronic doses of O₃ for 7 h a day and/or intermittent SO₂ fumigations (4 h a day, 3 days a week) from shortly after emergence until maturity. The O₃ was removed by charcoal filtration or applied by addition of various constant amounts of O₃ to the ambient O₃ present in non-filtered-air open-top chambers. There were no cultivar differences in yield response to either O₃ or SO₂. There also was no indication of an O₃ × SO₂ interaction. The data suggest yield losses of 5–15% at ambient O₃ concentrations (0·045-0·065 μl litre⁻¹) and about 7% yield loss due to 0·10 μl litre⁻¹ of SO₂ in intermittent exposures. These loss estimates for O₃ or SO₂ were similar to those of previously published studies from different areas of the United States utilising different soybean cultivars.