Submitted to: American Chemical Society Symposium Series
Publication Type: Book / Chapter
Publication Acceptance Date: 1/5/2002
Publication Date: 3/1/2004
Citation: Dabney, S.M., Yuan, Y., Bingner, R.L. 2004. Evaluation of best management practices in the Mississippi Delta Management Systems Evaluation Area. In: Nett, M.T., Locke, M.A., and Pennington, D.A., Editors. American Chemical Society. Washington, D.C. American Chemical Society Symposium Series 877. Water Quality Assessments in the Mississippi Delta: Regional Solutions, National Scope. pp. 61-74.
Interpretive Summary: Sediment has been identified as the pollutant most limiting to fish growth and reproduction in oxbow lakes in the Mississippi Delta. Farmers need economical ways of reducing sediment loss from their fields. We evaluated the cost effectiveness of several Best Management Practices (BMPs) designed to reduce sediment yield from agricultural fields in the Mississippi Delta. To do this, we used field measurements of a limited set of practice combinations collected in the Mississippi Delta MSEA (MDMSEA) project. We then extended the results to a wider set of BMP combinations using a computer simulation model called AnnAGNPS 2.0. BMPs considered included: no-till, reduced-till, cover crops, filter strips, grade control pipes, and impoundments. A cost/benefit analysis was conducted with a 25-year planning horizon. We found that reduced tillage together with the growth of winter weeds (cover crop), and a small permanent impoundment (covering <3% of the watershed) with conventional tillage were the most cost-effective ways of reducing sediment yield by at least 50% of that predicted for conventional tillage alone. Combining no-till, volunteer winter weeds, and an edge-of-field grade control pipe reduced sediment yeilds by nearly 90%. We also describe an innovative practice combination that is being currently evaluated: by surrounding the inlet of a grade-control pipe with a vegetative barrier, a temporary impoundment may trap sediment without removing additional land from production. Our work demonstrates the least costly ways for farmers to achieve various levels of reduction in sediment delivery from their fields to Delta oxbow lakes, ditches, and rivers.
Technical Abstract: Sediment has been identified as the pollutant most limiting to fishery health in oxbow lakes in the Mississippi Delta Management System Evaluation Area (MDMSEA). Best Management Practices (BMPs) with potential to cost-effectively reduce sediment yield from agricultural fields have been evaluated in a combination of field and computer modeling studies. BMPs considered included: no-till, reduced-till, cover crops, filter strips, grade control pipes, and impoundments. A cost/benefit analysis was conducted in which initial and future costs were combined into a single current cost using annuity calculations with a 25-year planning horizon. Benefits were determined using the Annualized Agricultural Nonpoint Source Pollutant Loading model (AnnAGNPS 2.0) to generalize measured scenarios. No-till and a small permanent impoundment (covering <3% of the watershed) were the most effective single practices for sediment reduction; each reduced sediment yield by at least 50%. Volunteer winter weeds as cover crops and edge-of-field grade control pipes were among the most cost-effective supplemental BMPs. An innovative combination of grade-control pipes surrounded by a vegetative barrier to create temporary impoundments is being currently evaluated in the MDMSEA and may achieve most of the sediment reduction benefits of small impoundments at lower cost.