Tony Vyn, professor of agronomy, found that no-till reduces NOX emissions by 57% over chisel tilling – which mixes crop residue into surface soil – and 40% over moldboard tilling, which completely inverts soil as well as the majority of surface residue. Chisel plowing is the most widely used form of tilling before planting corn in Indiana, he says.
"There was a dramatic reduction simply because of the no-till," says Vyn, whose findings were published in the Soil Science Society of America Journal. "We think the soil disturbance and residue placement impacts of chisel plowing and moldboard plowing modify the soil physical and microbial environments such that more NOX is created and released."
During early season nitrogen (N) fertilizer applications on corn, no-till may actually reduce NOX emissions from other forms of N present in, or resulting from, that fertilizer.
Nitrous oxide is the third-most abundant greenhouse gas in the atmosphere but, according to the U.S. Environmental Protection Agency, has about 310 times more heat-trapping power than carbon dioxide in part because of its 120-year lifespan.
"This suggests there is another benefit to no-till beyond soil conservation and improving water quality," Vyn says. "There is an air quality benefit, as well."
Using a corn-soybean rotation instead of continuous corn decreased NOX emissions by 20% in the three-year study. Vyn says 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% less N.
Vyn says finding ways to reduce NOX emissions is important because food production accounts for about 58% of all emissions of the gas in the U.S. Of that, about 38% is coming from the soil.
"There is more NOX emission coming from agriculture than the tailpipes of cars and trucks," Vyn says. "And there is likely to be more NOX emission if we increase N 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 N-based fertilizers to chemicals that can emit NOX.
A USDA 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.