Using a corn-soybean rotation instead of continuous corn decreased nitrous oxide emissions by 20 percent in the three-year study. Vyn said the reduction could be even greater, though, because for the long-term experiment, both continuous corn and rotation crops were fertilized based on the needs of continuous corn. A rotation cornfield would normally receive 20 percent less nitrogen.

Vyn said finding ways to reduce nitrous oxide emissions is important because food production accounts for about 58 percent of all emissions of the gas in the United States. Of that, about 38 percent is coming from the soil.

"There is more nitrous oxide emission coming from agriculture than the tailpipes of cars and trucks," Vyn said. "And there is likely to be more nitrous oxide emission if we increase nitrogen application rates to increase cereal yields."

The study took place on a consistently managed 30-year-old rotation/tillage experiment near Purdue.

The next step in Vyn's research is to develop integrated management practices to reduce nitrous oxide emissions even more. He's also studying additives that slow the conversion of nitrogen-based fertilizers to chemicals that can emit nitrous oxide.

A U.S. Department of Agriculture grant to the Consortium for Agricultural Soil Mitigation of Greenhouse Gases at Kansas State University funded the research. The Indiana Corn Marketing Council and Dow AgroSciences are funding his present on-farm studies of integrated management practices to reduce nitrous oxide emissions.