Rings of tubes emit ozone and carbon dioxide, both of which are expected to increase in the atmosphere in coming years. The gases hang over the crops before dissipating, allowing scientists to mimic predicted atmospheric changes.
"The crop is seeing the atmospheric condition we predict for 50 years from today," said Stephen P. Long, a University of Illinois professor of plant and biological sciences who heads the research known as soyFACE.
Scientists predict that Earth's atmosphere will contain 50 percent more carbon dioxide in 2050 than it did in 1900. While more carbon dioxide in the air contributes to global warming, it also increases the photosynthesis of plants, raising the potential for higher crop yield.
The Illinois experiment is testing how the rising levels of carbon dioxide and ozone will change agriculture. It uses technology known as Free-Air Concentration Enrichment to test the effect changes in the gases have on corn and soybeans, which together cover more than 150 million acres of land in the United States.
"It is possible that those changes could have a significant impact on all crops," said Kraig Wagenecht, executive director of the Illinois Council for Food and Agricultural Research, which provides most of the money for the project. "If we can anticipate what those changes are going to be... then we can today start various breeding programs that can adapt to those changes."
Now in their third year of work, soyFACE researchers have learned that higher concentrations of carbon dioxide raise yields in soybeans by up to 17 percent, while ozone, a major component of smog, lowers crop yield as much as 20 percent, Long said. They also have found that plants under increased carbon dioxide return less water to the atmosphere, a factor that could contribute to global warming.
"If we can understand how to adapt plants to take better advantage of carbon dioxide in the future, it might give us better yields today," Long said.
The research also could allow better predictions of the world's food supply, he said.
"The atmospheric change that is happening now is already having a significant effect on the quality and reliability of our crops and if we don't do anything about it, it is also going to affect our competitiveness" in world markets, Long said.
The project is located on 80 acres just south of the university's Urbana-Champaign campus. Researchers have laid out 16 plots in the field — four with elevated carbon dioxide, four with elevated ozone, four with higher levels of both gases and four control plots where nothing is changed.
Sensors inside each gas ring monitor wind speed and direction, and send the information to a computer that controls the gas flow, Long said. The rings use about a ton of carbon dioxide or about a pound of ozone per day, but it is diluted quickly so concentrations are close to normal within about 300 feet of a particular ring.
The experiments have no effect on human health, Long said.
While the technology is used in other experiments around the world, soyFACE is the only one that investigates the effect of changing atmospheric conditions on crops in an open-air environment, Long said.
"We're getting answers that could never have been speculated on before," said Ruth A. Reck, the director of the National Institute for Global Environmental Change, based at the University of California-Davis. Reck's institute is not involved in the Illinois experiments, which she said take a "vitally important" look into the future.
"We're testing the metabolism of this whole ecosystem," she said. "It's a different scale than biologists have been able to do before."