Nitrous oxide (N2O) is a potent greenhouse gas, with 300 times the warming ability of carbon dioxide. Due to fertilizer runoff from farm fields, an increasing load of nitrogen is washing into rivers and streams, where nitrogen-breathing microbes break some of the fertilizer down into N2O, which the river releases into the atmosphere as it tumbles toward the ocean. But, until now, scientists haven’t had a clear picture of how the process works, what fraction of the runoff winds up as N2O or what steps might be taken to mitigate N2O emissions.
