Submitted to: International Association of Environmental and Analytical Chemistry
Publication Type: Abstract Only
Publication Acceptance Date: May 10, 2004
Publication Date: August 16, 2004
Citation: Locke, M.A., Zablotowicz, R.M., Knight, S.S., Smith Jr., S., Lerch, R.N. 2004. Watershed research to assess conservation management and pesticide fate in lake water. International Association of Environmental and Analytical Chemistry. p. 38. Technical Abstract: The Mississippi Delta Management Systems Evaluation Area project (MDMSEA) began in 1994 as an assessment of conservation land management effects on environmental quality. Three oxbow lake watersheds were selected for evaluation (Thighman, Beasley, and Deep Hollow), using the premise that the lake was the recipient of most watershed drainage, thus improvements due to management would be manifested in lake water quality. For comparison, a hierarchy of management was used from one watershed to another, with the greatest intensity of conservation practices implemented at Deep Hollow (1996 to 2000), and the least at Thighman. Only edge-of-field practices (e.g., buffer strips, erosion control pipes) were used in Beasley until 2000. All watersheds were primarily planted to cotton and soybean in 1996, but by 2002, land use patterns shifted to include more corn, soybean, and in Beasley watershed, trees. Lake water samples were assessed for herbicides (fluometuron, atrazine, cyanazine, and metolachlor), total solids, phytoplankton, and nutrients from 1996 to 2002. Water quality of the three watersheds was dynamic and was influenced by land management practices and hydrology. Before improved practices were implemented in 1994-1995, lake ecology was impaired in all lakes due to sedimentation. During the period of assessment when management practices were implemented, primary productivity of lakes was restored. Overall, highest sediment levels, algal and bacterial populations, enzyme activities and herbicide levels (atrazine and metolachlor for corn production) were observed in Thighman Lake. Reduced tillage and glyphosate resistant crops (cotton / soybeans) (after 2000) in Beasley watershed resulted in lower levels of suspended sediments and herbicide concentrations in lake water. Reverting Deep Hollow watershed back to conventional tillage after 2000 increased fluometuron levels in lake water with little effect on suspended sediment.