Nitrogen-using bacteria can cut farms’ greenhouse gas emissions
By DIANA GITIG, Ars Technica.
Excerpt: Microbes in soil convert nitrogen fertilizer into nitrous oxide, and the more nitrogen fertilizer they have to work with, the more nitrous oxide they make. Agriculture also leaks plenty of the excess nitrogen into waterways in the form of nitrate, generating algal blooms that create low-oxygen ‘dead zones’ where no marine life can live. One way to reduce nitrogen emissions from farms would be to simply use fertilizer more efficiently. But—as we’ve seen with fossil fuels (and antibiotics and plastics)—when humans have a miraculous substance on our hands, we just can’t seem to use it at levels that minimize its impact. ...But even if we were to start using less fertilizer now, we are past time to choose a single technique to curb greenhouse gas emissions; we need to put them all into action. ...instead of trying to promote the growth of any denitrifying bacteria that might happen to already be in soil, researchers decided to grow them externally and then add them in. Their source was partially treated sewage, called digestate, that was destined as organic fertilizer anyway. Keeping the digestate in oxygen-free conditions enriched their levels of one strain of nitrogen-respiring bacteria. ...When this digestate was mixed into soil, fertilizer-induced emissions were reduced by 50–95 percent, depending on the pH and organic carbon content of the soils. The effect lasted over the entire growing season....