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United States Department of Agriculture

Agricultural Research Service

Research Project: MAINTAINING SOIL RESOURCES FOR EFFECTIVE CONSERVATION AND HERBICIDE MANAGEMENT IN MID-SOUTH CROP PRODUCTION

Location: Crop Production Systems Research Unit

Title: Effects of Land Management Practices on Water Quality in Mississippi Delta Oxbow Lakes: Biochemical and Microbiological Aspects

Authors
item Zablotowicz, Robert
item Zimba, Paul
item Locke, Martin
item Knight, Scott
item Lizotte, Richard
item Gordon, R Earl

Submitted to: Agricultural Research Service Publication
Publication Type: Government Publication
Publication Acceptance Date: September 15, 2008
Publication Date: N/A

Interpretive Summary: 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, Beasley, and Deep Hollow. Biochemical and microbiological studies can assess changes in lake health associated with microbial productivity, e.g., algae and bacteria. Results from the project during 2000-2003 are discussed. Monthly water samples were monitored for enzymatic activity, chemical and physical analysis, algal and bacterial populations. All these parameters were influenced by the nature of the watersheds, with some shifts observed with management changes on the surrounding agricultural fields. Introduction of reduced tillage practices and glyphosate resistant crops (cotton / soybeans) in Beasley watershed resulted in lower levels of suspended sediments, but had minimal impact on overall levels of biochemical or microbiological properties. Conversion of Deep Hollow watershed from reduced tillage to conventional tillage had little effect on suspended sediment, and most microbial activity parameters remained intermediate. Multivariate analysis indicated dynamic shifts in components of the microbial community suggesting that biological parameters of water quality of the lakes were affected by changes in crop management practices.

Technical Abstract: 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 (1497 ha, 9 ha lake); Beasley (850 ha, 25 ha lake); and Deep Hollow (202 ha, 8 ha lake). Results from the project during 2000-2003 are discussed. Monthly water samples were monitored for enzymatic activity (fluorescein diacetate hydrolysis, alkaline phosphatase, and substrate utilization [Biolog plate]) chemical and physical analysis (suspended solids, total organic carbon content, pH, and E.C.), phytoplankton populations (diagnostic photosynthetic pigments and most probable number assays), bacterioplankton populations (plate counts total and Gram-negative bacteria and coliform MPNs). All 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 sediment levels, dissolved organic carbon content, algal and bacterial populations, enzyme activities, and heterotrophic metabolic indexes. Introduction of reduced tillage practices and glyphosate resistant crops (cotton / soybeans) 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, cannonical analysis indicated dynamic changes in the microbial community suggesting that biological parameters of water quality of the lakes were affected by changes in crop and soil management practices.

Last Modified: 4/19/2014
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