Nitrogen runoff could be reduced by 45 percent in the Mississippi River basin – the heart of U.S. grain farming – with adoption of practices that reduce fertilizer waste and conversion of as little as 3.1 million acres of farmland to filter and hold nutrients that now flow downstream, says a research paper. Nitrogen runoff from farms and other sources is blamed for the “dead zone” in the Gulf of Mexico. The EPA has a goal of reducing nitrogen and phosphorus runoff by 45 percent to decrease the size of the low-oxygen zone to one-quarter or one-third of its usual size.
“Our results indicate that nitrogen-management practices (improved fertilizer management and cover crops) fall short of achieving this goal, even if adopted on all cropland in the region,” says the paper written by a seven-member team. “The goal of a 45 percent decrease in loads to the GoM (Gulf of Mexico) can only be achieved through the coupling of nitrogen-management practices with innovative nitrogen-removal practices such as tile-drainage treatment wetlands, drainage–ditch enhancements, stream-channel restoration, and flood-plain reconnection.”
The combination works best if applied throughout a watershed, “a different approach to conservation than that which has been so successful in addressing producer-identified resource concerns such as soil erosion,” says the paper, co-authored by Eileen McLellan of Environmental Defense Fund and Dale Robertson of Wisconsin Water Science Center.
The 2014 farm law created the Regional Conservation Partnership Project, a first step toward joint action to control a commonly shared problem such as runoff. The bulk of USDA conservation money is spent on cost-share projects on individual farms.
“(W)e believe that our conclusions are applicable to the Chesapeake Bay, Lake Erie and many other hypoxic areas around the world,” says the paper. More than 400 hypoxic, or dead, zones have been identified worldwide. The authors say they looked for techniques that would curtail runoff while minimizing impact on crop production. They included more efficient placement, application rates and timing of fertilizer and planting of cover crops to hold nutrients during the winter; efforts that could reduce nitrogen loss by 30 percent. With the nitrogen removal practices such as wetlands, the reduction would be 45 percent.