Evaluating Agricultural Best Management Practices in Tile-Drained Subwatersheds of the Mackinaw River, Illinois
- A. M. Lemke *a,
- K. G. Kirkhamb,
- T. T. Lindenbaumb,
- M. E. Herbertc,
- T. H. Teard,
- W. L. Perrye and
- J. R. Herkertf
- a The Nature Conservancy, 11304 N. Prairie Rd., Lewistown, IL 61542
b The Nature Conservancy, 301 SW Adams St., Suite 1007, Peoria, IL 61602
c The Nature Conservancy, 101 East Grand River, Lansing, MI 48906
d The Nature Conservancy, 1210 Hempstead Rd., Niskayuma, NY 12309
e Illinois State Univ., Dep. of Biological Sciences, Campus Box 4120, Normal, IL 61790
f Illinois Dep. of Natural Resources, One Natural Resources Way, Springfield, IL 62702. Assigned to Associate Editor Elizabeth Stockdale
Best management practices (BMPs) are widely promoted in agricultural watersheds as a means of improving water quality and ameliorating altered hydrology. We used a paired watershed approach to evaluate whether focused outreach could increase BMP implementation rates and whether BMPs could induce watershed-scale (4000 ha) changes in nutrients, suspended sediment concentrations, or hydrology in an agricultural watershed in central Illinois. Land use was >90% row crop agriculture with extensive subsurface tile drainage. Outreach successfully increased BMP implementation rates for grassed waterways, stream buffers, and strip-tillage within the treatment watershed, which are designed to reduce surface runoff and soil erosion. No significant changes in nitrate-nitrogen (NO3−–N), total phosphorus (TP), dissolved reactive phosphorus, total suspended sediment (TSS), or hydrology were observed after implementation of these BMPs over 7 yr of monitoring. Annual NO3−–N export (39–299 Mg) in the two watersheds was equally exported during baseflow and stormflow. Mean annual TP export was similar between the watersheds (3.8 Mg) and was greater for TSS in the treatment (1626 ± 497 Mg) than in the reference (940 ± 327 Mg) watershed. Export of TP and TSS was primarily due to stormflow (>85%). Results suggest that the BMPs established during this study were not adequate to override nutrient export from subsurface drainage tiles. Conservation planning in tile-drained agricultural watersheds will require a combination of surface-water BMPs and conservation practices that intercept and retain subsurface agricultural runoff. Our study emphasizes the need to measure conservation outcomes and not just implementation rates of conservation practices.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2011. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.