Location: Water Quality and Ecology Research2014 Annual Report
1a. Objectives (from AD-416):
Objective 1. Develop and evaluate farm and land management practices that reduce erosion, conserve soil, improve water quality, and protect ecological resources. Sub-objective 1a. Quantify the effects of conservation practices on runoff water quality and soil resources in Beasley Lake Conservation Effects Assessment Project (CEAP) watershed. Sub-objective 1b. Assess the influence of conservation practices on ecology and agricultural contaminant fate and transport in alluvial plain landscapes. Objective 2. Characterize and/or quantify the structure, function, and key processes of ecosystems in agricultural settings. Sub-objective 2a. Evaluate how nutrients, pesticides, and sediments interact with watershed hydrology to influence mechanisms regulating water quality and aquatic ecosystem structure and function in agricultural watersheds. Sub-objective 2b. Examine effects of water flow, climate-change-induced drought, and agricultural nutrient contaminants on stream microbial productivity and nutrient processing. Sub-objective 2c. Examine associations between fish species composition, hydrologic connectivity, and hypoxia in agricultural watersheds. Objective 3. Integrated assessment of the effects of agriculture on ecosystem services for watershed-scale endpoints. Sub-objective 3a. Develop integrated remote sensing tools to better evaluate wetlands and riparian buffers. Sub-objective 3b. Develop agricultural conservation strategies to adapt to climate change. Sub-objective 3c. Develop integrated modeling tools to assess the effectiveness of conservation practices that enhance ecosystem services at multiple scales. Objective 4. As part of the Long-Term Agro-ecosystem Research (LTAR) network, and in concert with similar long-term, land-based research infrastructure in Lower Mississippi River Basin (LMRB), use the Beasley Lake Experimental Watershed to improve the observational capabilities and data accessibility of the LTAR network, to support research to sustain or enhance agricultural production and environmental quality in humid environments characteristic of the LMRB, as per the LTAR site responsibilities and other information outlined in the 2012 USDA Long- LTAR Network Request for Information (RFI) to which the location successfully responded, and the LTAR Shared Research Strategy, a living document that serves as a roadmap for LTAR implementation. Participation in the LTAR network includes research and data management in support of the ARS GRACEnet and/or Livestock GRACEnet projects.
1b. Approach (from AD-416):
Long-term viability of U.S. agriculture depends upon implementation of management strategies that address goals of environmental sustainability and economic viability. Despite significant financial investment in conservation practices and water quality protection over recent decades, water quality issues remain unsolved in many agricultural landscapes. Off-site and downstream impacts of agricultural water pollution continue to raise concerns, most notably marine dead zones linked to excess nitrogen (N) and phosphorus (P). Biodiversity continues to decline due to water quality and habitat degradation. Future influences on environmental quality include synergistic effects of climate change, biofuel production, increased human population and exotic species. To address issues of water quality and watershed ecosystem function, investigations will pursue complementary approaches that consider the entire landscape, from upland fields to receiving water bodies. First, farm and land management technologies that reduce erosion, pesticide, and nutrient losses, conserve and improve soil, and protect ecological resources will be assessed. Second, studies will be conducted to improve understanding of structure, function, and key processes of aquatic systems, guiding better management of these systems and providing a scientific basis for regulatory agencies to establish water quality criteria. Third, investigations will develop and assess technology for improving water quality and ecosystem function in agriculturally impacted aquatic systems. Fourth, investigations will assemble and use long-term databases to develop and further enhance computer models for quantifying effects of conservation measures on agricultural watershed ecosystem services. This plan calls for experiments to be conducted across a range of spatial scales from the laboratory bench to the watershed.
3. Progress Report:
Long-term (1996-present) assessments in Conservation Effects Assessment Program (CEAP) Beasley Lake Watershed continue to demonstrate that a combination of management practices such as vegetative buffers, Conservation Reserve Program, and sediment basins contribute to: • Clearer lake water: Lower turbidity, higher secchi visibility, reduced total solids 65%, with improvements observed most strongly during the spring season. • Lower concentrations of total phosphorus and nitrate in lake water: Decreased over 50% during the study period. • Healthier lake conditions: Long-term nutrient, algae, and water clarity trends indicate Beasley Lake has shifted from a hyper-eutrophic to a more eutrophic condition. A project assessing ecosystem health of three Mississippi-Delta Bayou Watersheds since 2010 is continued and has demonstrated: • Shallow, low gradient, low-flow streams (bayous) are susceptible to land-use changes (crops and riparian acreage) causing seasonal excess sediment and nutrient loads and chronic low dissolved oxygen (hypoxia). • Bayou ecology is driven by seasonal combinations of light limitation (sediment), hyper-eutrophication (excess nutrients), and hydrology (water depth and flow). • Bayou algae have adapted to light limited, high nutrient, shallow conditions while fish populations and diversity are poor (low) under these conditions. • Nutrient-rich (hyper-eutrophic) lakes and bayous are used by farmers for irrigation, so hydrology (depth and flow) and water quality varies with growing season. A long-term study assessing runoff as influenced by field and edge-of-field management practices in corn showed reduction in off-site loss of sediment and nutrients associated with sediment, but loss of soluble nutrients and organic carbon were not significantly reduced. A new phase of the study will begin in fall 2014 with the integration of conservation and irrigation scheduling technologies in soybean to address water quantity and quality issues related to aquifer depletion. Studies utilize artificial stream mesocosms at the University of Mississippi Field Station to simulate agricultural streams. These experiments are showing: • Organic carbon inputs exacerbate dissolved oxygen minimums under no-flow and drought conditions while increasing the processing time of dissolved organic carbon. • Nitrogen and phosphorus inputs (eutrophication) followed by organic carbon inputs caused 12-18 hour hypoxic to anoxic conditions with and without flow. • Fish exposed to higher sediment concentrations gained more weight than fish in clear water. The hypothesis is that either sediments stimulate algae to supplement fish diet or that higher sediment improves swimming efficiency in certain fishes. Several research projects assess edge-of-field conservation practices such as ditch, buffer, and wetland management. These studies demonstrated that vegetation, in combination with weirs, reduced drainage flow, thus reducing sediment and chemical loss from ditch systems. Also, a water-level controlled natural wetland was effective in trapping sediment and chemicals, thus buffering negative ecological effects of chemicals. USDA Annualized AGricultural Non-Point Source (AnnAGNPS) pollutant loading model development and calibration continues. The modeling research demonstrated that utilizing buffers 5-40 m wide can filter up to 72-100% of sediment entering a buffer, although buffer efficacy is significantly reduced (to 3%) when concentrated flow (e.g., gullies) passes through buffers. Work is progressing to improve the riparian buffer component of the model with respect to water quality. A field experiment is conducted to test the hypothesis that long-term applications of glyphosate to both resistant and non-resistant corn under reduced and conventional tillage management impact soil characteristics and nutrient uptake. Preliminary results demonstrated no discernable differences in nutrient uptake or in soil and root rhizosphere microbial community structure and activity (based on genomics and exoenzymes) between the transgenic and non-transgenic corn cultivars. A new study was implemented to assess the efficacy of a tailwater recovery system to conserve water and improve water quality. Another new study was begun in collaboration with other ARS locations to assess the effects of flue-gas desulfurization gypsum and vegetative buffers on phosphorus runoff loss from corn. Involvement and leadership in the ARS Long-Term AgroEcosystem Research (LTAR) project was begun. Plans to develop and coordinate LTAR research in the Lower Mississippi River Basin are ongoing.
Lizotte Jr, R.E., Locke, M.A., Testa III, S. 2014. Influence of varying nutrient and pesticide mixtures on abatement efficiency using a vegetated free water surface constructed wetland mesocosm. Chemistry and Ecology. 30(3):280-294.