Nitrous oxide (N2O) is an important greenhouse gas (GHG) but it often takes a backseat in discussions about GHG emissions. This might be because it ranks third for GHGs emitted in the U.S. Carbon dioxide (CO2) is by far the number one GHG, making up 80 percent of GHG emissions. Methane (CH4) comes in second with 11 percent of the U.S. footprint from all sources. But for agriculture, the importance of all three gases is somewhat different than the national footprint.