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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Water Quality and Ecology Research » Research » Publications at this Location » Publication #356548

Research Project: Strategic Investigations to Improve Water Quality and Ecosystem Sustainability in Agricultural Landscapes

Location: Water Quality and Ecology Research

Title: Long-term oxbow lake trophic state under agricultural best management practices

item Lizotte, Richard
item Witthaus, Lindsey
item Bingner, Ronald - Ron
item Locke, Martin
item KNIGHT, SCOTT - University Of Mississippi

Submitted to: Water
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2021
Publication Date: 4/20/2021
Citation: Lizotte Jr, R.E., Witthaus, L.M., Bingner, R.L., Locke, M.A., Knight, S.S. 2021. Long-term oxbow lake trophic state under agricultural best management practices. Water. 13,1123.

Interpretive Summary: One of the main values of agricultural best management practices (BMPs) is to improve water quality and ecosystem services by decreasing nutrient enrichment or eutrophication. Eutrophication can be measured by assessing algae, water clarity and nutrient levels. Our study measured long-term (19-year) changes in summer eutrophication in an agriculturally influenced lake with a variety of BMPs placed in the watershed. Decreased eutrophication, seen as increasing water clarity and decreasing total phosphorus, over the first 10 years was associated with increased vegetative buffers, a sediment retention pond and conservation tillage. However, algae increased with conservation tillage and vegetative buffers while total nitrogen remained unchanged during the study. The study showed BMPs can modestly improve summer eutrophication but these improvements can be balanced by increases in algae. Our results are of interest to regulatory and management agencies and farming stakeholders by providing additional information to improve and sustain water quality and overall environmental quality using BMPs.

Technical Abstract: A key principle of agricultural best management practices (BMPs) is to improve water quality by reducing agricultural-sourced nutrients and associated eutrophication. Long-term (1998–2016) lake summer trophic state index (TSI) trends of an agricultural watershed with agricultural best management practices (BMPs) were assessed. Structural BMPs included vegetative buffers, conservation tillage, conservation reserve, a constructed wetland, and a sediment retention pond. TSI included Secchi visibility (SD), chlorophyll a (Chl), total phosphorus (TP), and total nitrogen (TN). Summer TSI 1977 was >80 in 1998–1999 (hypertrophic) and decreased over the first 10 years to TSI 1977 75 (eutrophic). TSI 1977 decrease and changing TSI deviations coincided with vegetative buffers, conservation tillage, and conservation reserve. The TSI(SD) decrease (>90 to <70) coincided with vegetative buffers and TSI(TP) decrease (>90 to <75) coincided primarily with conservation tillage and the sediment retention pond. TSI(Chl) increase (<60 to >70) coincided with conservation tillage and vegetative buffer. Results indicate watershed-wide BMPs can modestly decrease summer trophic state through increased water transparency and decreased TP, but these changes are off-set by increases in chlorophyll a to reach a new stable state within a decade. Future research should assess algal nutrient thresholds, internal nutrient loading, and climate change effects.