Farm wetlands doing their job

LEXINGTON, Ill. — An example of how nature and agriculture can coexist to benefit crop production, water quality and habitat preservation was among the stops during the recent From Farm to Filtration: A Tour of Conservation in Action.

Hosted by the McLean County Soil and Water Conservation District, Purdue University, Illinois Nutrient Research and Education Council, The Nature Conservancy and Illinois Sustainable Ag Partnership, the tour highlighted how drainage tile impacts water quality, cover crops’ role in nutrient management, utilizing wetlands to limit nutrient runoff and the costs associated with treating nutrients in the water.

One of the featured stops was at the Franklin Research and Demonstration Farm in Lexington, a site with over two decades of research on agricultural practices that benefits both farmers and conservation efforts in the Mackinaw River watershed.

Through a cooperative agreement between TNC and the Franklin family, 140 acres of the farm were transformed into a place where farmers and others can learn firsthand about agricultural practices that benefit nature.

The initial partnership between John Franklin’s family, researchers and conservation partners began in 2004.

Three wetlands were constructed between 2004 and 2006, each consisting of three wetland cells separated by berms. Water gravity-flows between cells through tiles installed within the berms, and perimeter berms prevent surface water runoff from entering the wetlands.

Tile systems drain water into the wetlands where plants absorb some of the nutrients and microbes convert some of the nutrients into nitrogen gas, an inert, non-greenhouse gas.

Wetland plants can also sequester carbon from the air.

“We started putting in the monitoring equipment late in 2006, and then we started collecting data by 2007. We’ve been out here a long time collecting a water quality data,” said Krista Kirkham, TNC aquatic ecologist.

The automated water quality monitors were installed at each inlet and outlet of the wetland cells to collect samples.

An Agri Drain control system was installed at a permanent depth so the wetlands can retain as much water as possible. A water transducer monitors water depth and flow.

“Each one of the wetlands are not the same size, and that was done on purpose. These are representing 3%, 6% and 9% of the drainage area coming into it. This is a way to be able to determine how big of a wetland you really need to see the actual improvements of nitrogen and phosphorous levels coming through the tile drainage,” Kirkham said.

Data-Driven

Fifteen years of data showed that a smaller gully wetland representing 3% of the adjacent tile-drainage field can successfully reduce nitrate nitrogen levels by 15% to 38% and dissolve phosphorous by 52% to 81%.

The midsized wetland that treated 6% of the tile-drained farmland showed a cumulative reduction of nitrate nitrogen levels in water by 39% to 49%.

The wetland representing 9% of the tile-drained farmland had a cumulative reduction of 49% to 57% in nitrogen levels in the water.

“These wetlands work and they don’t have to be very big to work, and that’s what we hoped to find. That was great news, so to be able to tell that out to the farming community that these work and they don’t have to be very big,” Kirkham said.

“We’ve also been working in other watersheds to help implement other constructed wetlands under the Farmable Wetlands Program. I believe we helped put in seven wetlands in the Lake Bloomington watershed and a few others outside the Colfax area where we have a long-term project, as well.”

Other Studies

Researchers have expanded their efforts at the site, examining how combining wetlands with various in-field practices might reduce the nutrient loss.

“We incorporated a cover crop study here for the past 10 years, looking at the data to see what the impact will be,” Kirkham said.

“Another thing we did for the past two years where there was corn on the east side, we worked with the tenant to not apply nitrogen in the fall and only do a spring application. Early results seemed pretty strong that that makes a big difference.”

The farm also features a woodland savanna, a restored prairie, floodplain wetlands and grassed waterways.