Wetlands provide valuable ecosystem services and many economic benefits to communities. Unfortunately, much of the original wetland habitat in the United States has been lost. In Illinois, over 90% of original wetland acreage has been converted for urbanization and agriculture. Approximately 39% of Illinois’ agricultural acres are tile-drained, emphasizing the importance of edge-of-field practices to help reduce nutrient contributions to the Gulf of Mexico.
The Nature Conservancy, University of Illinois, and the Franklin Family have partnered since 2005 on the 101-hectacre Franklin Research and Demonstration Farm (FRDF) in Lexington, IL. This farm showcases various agricultural conservation practices, including sequential constructed wetlands that represent 3%, 6%, and 9% of farm drainage areas. Twelve years of water quality analysis demonstrate that the wetlands removed an average of 15%-57% of nitrate-nitrogen and 32%-95% of dissolved phosphorus loadings from tile drainage waters. Since the phosphorus (P) cycle lacks an atmospheric removal pathway, the capacity of wetlands to sequester P often decreases over time as the availability of soil sorption sites declines. US Army Corp of Engineers soil scientists evaluated the P sorption capacity of the FRDF treatment wetlands and found that the wetlands sequestered P, with water soluble P displaying significant decreases in sequential treatment cells (61.0 – 81.7% reduction). Soil P sorption capacity increased in the direction of treatment water flow as anticipated but varied significantly between treatment wetlands with soils ranging from P sinks to potential P sources.
In addition to the FRDF, The Nature Conservancy and conservation partners have worked with other Illinois landowners over the past several years to install constructed wetlands for cropland drainage treatment under USA Farm Bill programs. Our goals were to support landowner outreach while improving wetland engineering, operation and maintenance, and water quality monitoring. Our collective aim is to support conservation professionals and landowners that install constructed wetlands to ensure wetland functionality and longevity.