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Effectiveness of Constructed Wetlands in Reducing Nitrogen and Phosphorus Export from Agricultural Tile Drainage
Author(s) -
Kovacic David A.,
David Mark B.,
Gentry Lowell E.,
Starks Karen M.,
Cooke Richard A.
Publication year - 2000
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2000.00472425002900040033x
Subject(s) - tile drainage , wetland , environmental science , hydrology (agriculture) , drainage , surface water , nutrient , evapotranspiration , phosphorus , subsurface flow , buffer strip , surface runoff , soil water , agronomy , environmental engineering , groundwater , ecology , soil science , chemistry , geology , geotechnical engineering , organic chemistry , biology
Much of the nonpoint N and P entering surface waters of the Midwest is from agriculture. We determined if constructed wetlands could be used to reduce nonpoint N and P exports from agricultural tile drainage systems to surface waters. Three treatment wetlands (0.3 to 0.8 ha in surface area, 1200 to 5400 m 3 in volume) that intercepted subsurface tile drainage water were constructed in 1994 on Colo soils (fine‐silty, mixed, superactive, mesic Cumulic Endoaquoll) between upland maize ( Zea mays L.) and soybean [ Glycine max (L.) Merr.] cropland and the adjacent Embarras River. Water (tile flow, precipitation, evapotranspiration, outlet flow, and seepage) and nutrient (N and P) budgets were determined from 1 Oct. 1994 through 30 Sept. 1997 for each wetland. Wetlands received 4639 kg total N during the 3‐yr period (96% as NO 3 ‐N) and removed 1697 kg N, or 37% of inputs. Wetlands decreased NO 3 −N concentrations in inlet water (annual outlet volume weighted average concentrations of 4.6 to 14.5 mg N L −1 ) by 28% compared with the outlets. When the wetlands were coupled with the 15.3‐m buffer strip between the wetlands and the river, an additional 9% of the tile NO 3 −N was apparently removed, increasing the N removal efficiency to 46%. Overall, total P removal was only 2% during the 3‐yr period, with highly variable results in each wetland and year. Treatment wetlands can be an effective tool in reducing agricultural N loading to surface water and for attaining drinking water standards in the Midwest.