LEXINGTON, Ill. – A long-term study of constructed wetlands in Illinois by The Nature Conservancy (TNC) and others shows a nearly 50 percent reduction of excess nutrients in agricultural runoff that can damage wildlife habitat and impact water quality.

John Franklin’s farm has been in his family for 170 years. He believes in conservation because he wants to keep it going for the next generation. Franklin, his brother, and other family members raise corn and soybeans on his property in Lexington, bordering the Mackinaw River.

When he heard that TNC was looking for a site to try innovative farming techniques, he offered up 140 acres of his farm. TNC has been using a portion of this site for experiments since 2005 to explore how constructed wetlands can reduce nutrient runoff from farm fields.

“As a longtime Illinois farmer, I know we need to protect our waterways,” Franklin said. “We all live downstream of someone else, after all. And farmers want to keep our nutrients in our soil. This study shows that it’s possible through creative solutions, but we can’t afford to bear all of the cost.”

The 12-year study by TNC, the U.S. Army Corps of Engineers and the University of Illinois shows that small, edge-of-field wetlands can help address runoff by capturing excess nutrients from the agricultural tile drain systems that help maintain productive farmlands.

Dr. Maria Lemke, director of conservation science at The Nature Conservancy in Illinois, and others recently published the study results from Franklin’s farm on a series of wetland complexes they installed. They designed the wetlands to determine how large a wetland is needed to treat water coming through agricultural drainage tile systems effectively.

“That was our overarching question initially, and the wetlands were designed to answer that,” Lemke said. “We set up a series of what we call wetland complexes. Each complex was a series of three wetlands that were all the same size but were connected.”

The first wetland represented 3 percent of the tiled area, the first two wetlands combined represented 6 percent, and all three combined represented 9 percent, Lemke said. Each had an inlet and an outlet.

“We have monitored the inlets of each of those wetlands,” Lemke said. “We could see what was coming into the first one from the field, how well that first small wetland treated that, and we knew what was coming in from that first wetland into the second wetland and what was leaving the second wetland and then what was going into the third one.”

The researchers monitored the volume of water moving into and out of the wetlands, the nitrate (dissolved forms of nitrogen), and the dissolved phosphorous. They found that even a small wetland (about 6 percent of the cultivated area) can slash the excess nitrogen in water by nearly half and remove more than half of dissolved phosphorus.

Each year, excess phosphorous and nitrates flow from midwestern farms into streams and rivers, contributing to a cyanobacterial bloom that can impair local drinking water and ultimately lead to a marine “dead zone” in the Gulf of Mexico that threatens marine life and local economies.

Agricultural landowners and farmers in the Mackinaw River watershed of central Illinois have worked with TNC and partners since 2005 to integrate more than 20 wetlands into farm operations, 16 designed specifically to intercept and treat tile drainage.

But more help is needed. Illinois is one of 12 midwestern states (Indiana, Kentucky, Ohio and Tennessee are also included) that have developed nutrient loss reduction plans to reduce nutrient export from Illinois rivers to the Mississippi River and the Gulf of Mexico.

Yet a recent assessment from the Illinois Nutrient Loss Reduction Strategy (NLRS) reports that nitrogen levels in Illinois waterways have increased by 13 percent and phosphorus by 35 percent from baseline conditions. Illinois will unlikely meet its water quality targets without a dramatic increase in the pace and scale at which wetlands and other tile-treatment practices are implemented.

While wetlands are beneficial, installing one can be difficult and costly. Farmers can receive compensation through the Conservation Reserve Program, Environmental Quality Incentives Program and other programs, but they often must pay out of pocket and wait for reimbursement. Plus, although environmentally helpful, landowners see few personal benefits.

Ashley Maybanks, TNC’s director of government relations, does what she can to encourage public funding to go toward conservation practices like wetlands for nutrient reduction purposes.

“The most relevant and recent policy effort that would support additional conservation practices like wetlands is the passage of the Federal Inflation Reduction Act,” Maybanks said. “That act provides about $19 billion nationwide for ag and conservation practices like the Conservation Stewardship Program and the Environmental Quality Incentives Program.”

Those programs are currently oversubscribed three to one, meaning that there are three to one more applications in the queue than there is funding for, Maybanks said. 

“Hopefully that bill will open opportunities and get more funding for those kinds of projects. The next Farm Bill could help if it includes more funding for the conservation reserve program,” she said.

“We have a long way to go,” Franklin said, “but farmers have an incentive to do this, to become part of the solution in reducing nutrient runoff.”