Main content area

Effects of land management practices on water quality in Mississippi Delta oxbow lakes: Biochemical and microbiological aspects

Zablotowicz, R.M., Zimba, P.V., Locke, M.A., Knight, S.S., Lizotte, R.E., Gordon, R.E.
Agriculture, ecosystems & environment 2010 v.139 no.1-2 pp. 214
land management, deltas, oxbow lakes, water quality, biochemistry, surface water, enzyme activity, alkaline phosphatase, enzyme substrates, enzymatic hydrolysis, hydrochemistry, total suspended solids, dissolved organic carbon, pH, nitrate nitrogen, ammonium nitrogen, electrical conductivity, orthophosphates, phytoplankton, bacterioplankton, agricultural watersheds, heterotrophs, conservation tillage, tillage, Mississippi
The Mississippi Delta Management Systems Evaluation Area (MSEA) project was designed to assess the effects of land management practices on water quality in three small oxbow lake watersheds; Thighman (1338ha, 16ha lake); Beasley (915ha, 25ha lake); and Deep Hollow (132ha, 8ha lake). Monthly water samples were monitored for enzymatic activity (fluorescein diacetate hydrolysis, alkaline phosphatase, and substrate utilization), chemical and physical analysis (suspended solids, dissolved organic carbon, pH, nitrate, ammonium, orthophosphate, and electrical conductivity), phytoplankton and bacterioplankton populations. All of these parameters were influenced by the intrinsic nature of the watersheds, with some parameters shifting as management changes were imposed on the surrounding agricultural fields. Thighman lake water typically maintained the highest suspended solid levels, dissolved organic carbon, algal and bacterial populations, enzyme activities, and heterotrophic metabolic indexes. Introduction of reduced tillage practices and glyphosate-resistant crops in Beasley watershed resulted in lower levels of suspended sediments, but had minimal impact on overall ranking of biochemical or microbiological properties. Likewise, conversion of Deep Hollow watershed from reduced tillage to conventional tillage had little effect on suspended sediment, and most microbial activity parameters remained intermediate. However, canonical analysis indicated dynamic changes in the microbial community, suggesting that biological parameters of lake water quality were affected by changes in crop and soil management practices.