A new study shows converting some crops to perennial grasses could reduce the amount of chemicals flowing from farm fields into rivers and streams. Researchers used models to calculate how much the flow of nitrogen into the Mississippi River’s dead zone could be reduced if certain amounts of farmland grew switchgrass or miscanthus instead of their current crops.
Iowa State University agronomist Andy Vanloocke, who worked on the study, says the results show that the grasses can help, but are not a silver bullet. “Perennial biofuels are an effective land use management, or likely an effective land use management, when it comes to trying to improve water quality. But they are not the only way to go,” Vanloock says.
The grasses also could prevent water from flowing downstream. So the study considered streamflow as well as nutrient movement. “We would like to see a scenario where streamflow is status quo, where it stays as close to where it has been as possible, but where that water is flowing has as little nitrogen in it as possible as well,” Vanloocke says.
Switchgrass or miscanthus could be used as feedstock for cellulosic ethanol, but currently the commercial markets for the grasses pale in comparison to those for corn or soybeans. Vanloocke says the grasses offer the most gain for areas that currently send the most nutrients downstream, such as places with high rainfall.
The report appears in the journal Global Change Biology Bioenergy.
(Reporting by Amy Mayer and photo by Rick Fredericksen, both Iowa Public Radio)