A study published in the 14 March online early edition of New Phytologist suggests that rising levels of ozone starting at the Earth’s surface (tropospheric ozone) could reduce soybean harvests. Ozone is formed via the interaction of oxides of nitrogen (NOx) and sunlight.
Mean surface ozone concentration is predicted to increase 23% by 2050. The researchers increased the ozone concentration by 23% from an average daytime ambient 56 ppb to 69 ppb, and found that seed yield decreased by 20%.
|FACE set-up for experimentation.|
Researchers at the University of Illinois and US Department of Agriculture ARS used free-air gas concentration enrichment (FACE) technology for ozone fumigation of soybean crops over two growing seasons—the first such study using FACE with a foodcrop.
Prior studies on foodcrops have used chamber studies—small greenhouse-like enclosures that create conditions that are too different: warmer, less precipitation, more humid. A FACE study, however, uses a larger area, with no artificial enclosure.
Total above-ground net primary production decreased by 17% without altering dry mass allocation among shoot organs, except seed. Fewer live leaves and decreased photosynthesis in late grain filling appear to drive the ozone-induced losses in production and yield.
The team noted that yield losses with elevated ozone were greater in the second year following a severe hailstorm, suggesting that losses caused by ozone might be exacerbated by extreme climatic events.
“Season-long elevation of ozone concentration to projected 2050 levels under fully open-air conditions substantially decreases the growth and production of soybean”; Patric Morgan, Timothy Mies, Germán Bollero, Randall Nelson, and Stephen Long; New Phytologist; doi: 10.1111/j.1469-8137.2006.01679.x