This June 13, 2007, photo shows corn being grown to produce ethanol, in a field in London, Ohio. In the world of greenhouse gas emissions, carbon dioxide gets most of the blame. But tiny organisms that flourish in the world's farm fields emit a far more potent gas, nitrous oxide, and scientists have long sought a way to address it. (AP Photo/Kiichiro Sato, file)
FILE - In this April 28, 2004, file photo Mearl McCartney plants soybeans using a no-till drill near Bowling Green, Ohio. In the world of greenhouse gas emissions, carbon dioxide gets most of the blame. But tiny organisms that flourish in the world's farm fields emit a far more potent gas, nitrous oxide, and scientists have long sought a way to address it. (AP Photo/J.D. Pooley, File)