Farm fertilizer produces greenhouse gas; emissions can be reduced by adding less nitrogen

Greenhouse gas produced in the soil following nitrogen addition rises faster than previously expected when fertilizer rates exceed crop needs, according to a study by researchers at Michigan State University published in the journal Proceedings of the National Academy of the Sciences. Adding less nitrogen to overfertilized crops "would deliver major reductions to greenhouse gas emission," researchers said.

"Nitrogen-based fertilizers spur greenhouse gas emissions by stimulating microbes in the soil to produce more nitrous oxide," researchers said. "Nitrous oxide is the third most important greenhouse gas—behind only carbon dioxide and methane—and also destroys stratospheric ozone. Agriculture accounts for around 80 percent of human-caused nitrous oxide emissions worldwide, which have increased substantially in recent years, primarily due to increased nitrogen fertilizer use."

Phil Robertson, director of MSU’s Kellogg Biological Station Long-term Ecological Research Program and senior author of the paper, said, “Our specific motivation is to learn where to best target agricultural efforts to slow global warming. Agriculture accounts for 8 to 14 percent of all greenhouse gas production globally. We’re showing how farmers can help to reduce this number by applying nitrogen fertilizer more precisely.” (MSU photo: Phil Robertson)

The production of nitrous oxide can be reduced if "plant nitrogen needs are matched with the nitrogen that’s supplied," then "fertilizer has substantially less effect on greenhouse gas emission," Roberston said. Lead author Iurii Shcherbak added, “Because nitrous oxide emissions won’t be accelerated by fertilizers until crop nitrogen needs are met, more nitrogen fertilizer can be added to underfertilized crops with little impact on emissions." (Read more)