Wetlands Filter Out Nutrients
Wetlands, funded through programs such as the Conservation Reserve Program and the Environmental Quality Incentives Program, are expected to be a key tool in
reducing the amount of nitrogen (N) and phosphorus (P) escaping from farm fields through tile drainage water. Eventually, the nutrients make their way into the Gulf of Mexico, where they create algae blooms that deplete the water of oxygen, destroying marine habitat.
But how many acres of wetlands might be needed? Part of the answer will come from the Franklin Demonstration Farm, near Lexington, Ill., where researchers are running water from a tile system through constructed wetlands before it reaches the Mackinaw River.
After two years, research suggests a wetland/cropland ratio of 3% can remove 18% of the N and 43% of the P. A ratio of 6% wetlands removed 34% of the N and 55% of the P. With 9% of the area in wetlands, 43% of the N and 56% of the P were removed.
Not all the wetlands required taking land out of production, notes Nature Conservancy (www.nature.org) aquatic ecologist Maria Lemke. "Some of them were constructed in uncropped areas or cropland that was prone to flooding," she says.
Within a year, researchers hope to have enough data to generate ratios that could be applied to other farms.
Besides the Conservancy, partners include the University of Illinois, the McLean County Soil and Water Conservation District, the Natural Resources Conservation Service and the Franklin family of Lexington, Ill. The Illinois Department of Natural Resources funded the initial project, and a gift from Monsanto Company will fund three more years of water monitoring.
On the Franklin farm, new tile systems were installed for research purposes. But that won't be necessary for every application, Lemke says. "On most farms, we can reroute the existing tile system's outlet through the wetland."
Pheasants Forever Will Preserve a Kansas Farm
"When you have literally sweated, bled and cried over a place, you don't want to see it broken up," says Wallace Weber of Dorrance, Kan.
- March 2009