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Research Project: Integrated Strategies for Improved Water Quality and Ecosystem Integrity within Agricultural Watersheds

Location: Water Quality and Ecology Research

2016 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 the Conservation Effects Assessment Program (CEAP) Beasley Lake watershed continue to demonstrate effectiveness of integrated management practices including vegetated buffers, sediment retention basins, and Conservation Reserve Program (CRP) acreage at reducing concentrations of total solids, nitrate, and phosphorus being transported from production acreage into the lake. As a result, Beasley Lake water clarity improved, and these improved parameters have resulted in lake conditions shifting from hyper-eutrophic to eutrophic. On-going ecological assessments in Mississippi-Delta Bayou watersheds since 2010 continue to identify factors influencing ecosystem health in agriculturally-influenced bayous. Variation in cropping patterns and conservation practices influence seasonal patterns of excess sediment and nutrient loads in the shallow, low-gradient, low-flow bayou systems. An assessment on the interaction of light and nutrients on algal nutrient limitation has been completed, has have multiple organic matter processing studies. These studies demonstrate rapid breakdown of agriculturally derived and natural riparian organic matter combined with excess nutrients influence dissolved oxygen dynamics in bayou ecosystems. A GIS database has been constructed for each watershed, and cropping patterns are updated annually. Because farmers use these bayous for irrigation, water depth, flow, and quality varies by season. Depth manipulation on one lake that includes a weir (to increase depth) was conducted through a drawdown study completed in Fall 2015, with data collection on-going. Several research projects assess edge-of-field conservation practices such as ditch and wetland management. These studies demonstrated species specific differences in denitrification rates, finding that cutgrass removed 30 times more nitrate than cattails or unvegetated sediment. Winter experiments demonstrated that dead cutgrass still serves as a significant sink for nitrogen, releasing less than 10% of previously-retained nitrogen. Additional studies on nutrient mitigation and potential denitrification in mixed plant systems have been initiated. USDA Annualized AGricultural Non-Point Source (AnnAGNPS) pollutant loading model enhanced wetland features. The modeling research demonstrated an integrated watershed systems approach to quantitatively evaluate wetlands as potential conservation management alternatives. This technology provides conservationists the capability for improved management of watershed systems and support for nutrient credit trading programs. A new version (AnnAGNPS v5.44) that includes integrated tillage, gully, wetland and riparian buffer components has been released. Significant progress was made on a study assessing the ability of a tailwater recovery system to not only improve water quality, but also to conserve water use. Continuous monitoring and flow-triggered sampling during runoff events are now active at all field outlet pipes leading to the tailwater recovery ditch. Two years of bi-monthly water quality sampling and one year of storm sampling have been completed and are being analyzed. Routine and storm sampling currently continue and are planned to continue through the next project plan cycle. Preliminary water quality results indicate mitigation of nutrients within the ditch, resulting in lower nutrient concentrations leaving the agricultural drainage. Involvement and leadership in the Agricultural Research Service (ARS) Long-Term AgroEcosystem Research (LTAR) project continues. Unit scientists are engaged and coordinating with the national LTAR network in the development of the common experiment, measurement approaches, infrastructure needs, and data management. Efforts are underway to establish both business-as-usual and aspirational long term agricultural research sites in rice-soybean production systems in the Mississippi Delta region.

4. Accomplishments
1. Enhanced watershed management planning technology available. A new version (v5.44) of the Annualized Agricultural Non-Point Source (AnnAGNPS) watershed planning tool was released with enhanced gully, wetland and riparian buffer components. These components are critical in development of integrated conservation management practice watershed plans. It provides watershed conservation managers with technology to implement the efficient placement of practices with minimum utilization of resources.

2. Mowing vegetation in ditches still allows for nutrient mitigation. Small-scale field trials compared the nitrogen and phosphorus concentrations in runoff through vegetated agricultural drainage ditches that had been mowed and an equal number that were left undisturbed. No significant differences in nutrient concentrations between ditch type (mowed vs. undisturbed) were noted. Results suggest farmers can maintain their ditches through mowing, an important aesthetic and pest control feature, while still providing nutrient reduction capacities. This provides beneficial management strategies to be utilized by farmers and landowners in maintaining vegetated drainage ditches.

3. Nutrient mitigation best achieved with aquatic plant mixtures in wetlands and ditches. Mesocosm experiments compared the nitrogen and phosphorus retention capability of six different aquatic plants against each other and against an unvegetated control over two summers. Cattails (Typha latifolia) had significantly better phosphorus retention than the control and other plants during both summer experiments. Other aquatic plants had significant nutrient retention in the first summer, but results from the second summer were not significant. This research highlights the inherent variability among different aquatic plants used for nutrient uptake. As a result, researchers are now examining different plant mixtures to determine optimum nutrient mitigation. With this increased understanding, farmers and landowners can better design management systems to decrease nutrient input into downstream receiving systems.

5. Significant Activities that Support Special Target Populations:

Review Publications
Murdock, J.N. 2015. Detecting carbon uptake by individual algae in multi-species assemblages. American Society of Limnology and Oceanography. 14(2):124-137 DOI:10.1002/lom3.10078.

Keating, M.P., Balachandran, D., Ochs, C.A., Holland, M.M., Lizotte Jr, R.E., Yu, K. 2015. Spatial variation related to hydroloigc patterns and vegetation in greenhouse gas fluxes from the Mississippi Delta agricultural region. Applied Soil Ecology. 98:278-281 DOI: 10.1016/j.apsoil.2015.09.012.

Dash, P., Ikenga, J., Silwal, S., Pinckney, J., Arslan, Z., Lizotte Jr, R.E. 2015. Water quality of four major lakes in Mississippi, USA: Impacts on human and aquatic ecosystem health. Water Research. 7:4999-5030. doi: 10.3390/w7094999.

Chen, J.G., Chakravarty, P., Davidson, G.R., Wren, D.G., Locke, M.A., Zhou, Y., Cizdziel, J.V. 2015. Simultaneous determination of mercury and organic carbon using a direct mercury analyzer: Mercury profiles in sediment cores from oxbow lakes in the Mississippi Delta. Analytica Chimica Acta. 871:9-17.

Iseyemi, O.O., Farris, J.L., Moore, M.T., Choi, S. 2016. Nutrient mitigation efficiency in agricultural drainage ditches: An influence of landscape management. Bulletin of Environmental Contamination and Toxicology. 96:750-756.

Moore, M.T., Kroger, R., Locke, M.A. 2016. Drying and storage methods affect cyfluthrin concentrations in exposed plant samples. Bulletin of Environmental Contamination and Toxicology. 2016;97:244-248.

Moore, M.T., Locke, M.A., Kroger, R. 2016. Using aquatic vegetation to remediate nitrate, ammonium, and soluble reactive phosphorus in simulated runoff. Chemosphere. 2016; 160:149-154.

Wren, D.G., Rigby Jr, J.R., Davidson, G.R., Locke, M.A. 2016. Determination of lake sediment accumulation rates in an agricultural watershed using lead-210 and cesium-137. Journal of Soil and Water Conservation. 71(2):137-147; doi: 10.2489/jswc.71.2.137.

Bingner, R.L., Wells, R.R., Momm, H., Rigby Jr, J.R., Theurer, F.D. 2016. Ephemeral gully channel width and erosion simulation technology. Natural Hazards. 80(3):1949-1966.

Taylor, J.M., Back, J.A., Brooks, B.W., King, R.S. 2016. Consumer-mediated nutrient recycling is influenced by interactions between nutrient enrichment and the anti-microbial agent triclosan. Freshwater Science. 2016. 35(3):856-872. DOI: 10.1086/687838.

Li, H., Cruse, R.M., Bingner, R.L., Gesch, K.R., Zhang, X. 2015. Evaluating ephemeral gully erosion impact on Zea mays L. yield and economics using AnnAGNPS. Soil & Tillage Research. 155:157-165.