Location: Water Quality and Ecology Research2015 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 integrated management practices that include vegetative buffers, Conservation Reserve Program, and sediment basins have reduced total solids by 65%, contributing to clearer lake water and reduced concentrations of total phosphorus and nitrate in lake water by over 50%, thus resulting in healthier lake conditions that have ultimately shifted Beasley Lake from a hyper-eutrophic to a more eutrophic condition. On-going ecological assessments in three Mississippi-Delta Bayou Watersheds since 2010 continue to identify factors that influence ecosystem health in agriculturally influenced bayous. Variation in cropping patterns and conservation practices influence seasonal patterns of excess sediment and nutrient loads in shallow, low gradient, low-flow streams (bayous). New studies conducted in experimental mesocosms combined with field studies demonstrate that rapid breakdown of both riparian and agriculturally derived organic matter combined with excess nutrients influence dissolved oxygen dynamics in bayou ecosystems. 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. Manipulation of water levels in one watershed is planned for fall 2015 to experimentally assess ecological consequences of fluctuating water levels. 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 began in 2015 that integrates conservation and irrigation scheduling technologies in soybean production and addresses 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 demonstrated that 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 species specific differences in denitrification rates and found that cutgrass permanently removed 30 times more nitrate through the denitrification process than cattail or unvegetated sediments. A winter experiment also demonstrated that dead cutgrass can serve as a significant nitrogen sink during winter storm events while releasing relatively little bound phosphorus back to aquatic environments. Additional studies on nutrient mitigation properties of cutgrass have been initiated with a graduate student and university faculty collaborator. 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 new version (AnnAGNPS v5.43) that includes enhanced gully, wetland and riparian buffer components has been released. Progress was made in a study that is assessing the efficacy of a tailwater recovery system to conserve water and improve water quality. All sites where water transfers between system components are now being monitored continuously for hydrology, pesticides, sediments, nutrients, and water quality. A simulated runoff experiment is planned for fall 2015 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 Agricultural Research Service (ARS) Long-Term AgroEcosystem Research (LTAR) project continues. Research 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 have been initiated to establish both business-as-usual and aspirational long term agricultural research sites in rice-soybean production systems in the Mississippi Delta region.
1. Borrow pits excavated for flood-control levee construction along rivers increase fish community diversity and size. Fish surveys also demonstrated that nearly a dozen species not typically found in stream channels were located in these borrow pits. This demonstrates the opportunity for created habitats to mitigate negative impacts associated with flood control projects, offering watershed managers unique opportunities to improve fish diversity in rivers and streams.
2. Chemical analyses, fauna sampling, and bioassays showed no detrimental effects associated with runoff collected from an on-farm water storage reservoir and its associated tailwater ditch. This is good news because on-farm water reservoirs for storage and re-use of irrigation water (tailwater recovery) are being constructed in the lower Mississippi Delta to provide a water supply alternative to pumping groundwater. This research is crucial given the recent Environmental Protection Agency (EPA) Clean Water Rule issuance that could impact agricultural wetlands and ditches.
3. A common grass species (cutgrass) converts nitrogen dissolved in water to nitrogen gas at rates 30 times higher than observed for agricultural ditch environments planted with cattails or without plants. These experimental research results indicate, that ditches planted with cutgrass have the potential to permanently remove 50% of nitrogen captured from agricultural runoff and serve as an important nitrogen mitigation practice on agricultural lands.
4. A new version (Ver. 5.43) of Annualized AGricultural Non-Point Source (AnnAGNPS) watershed management planning tool was released with enhanced gully, wetland and riparian buffer components. These enhancements are critical to the development of integrated conservation management practice watershed plans and will help watershed conservation managers evaluate effectiveness of conservation practices by providing unique information about the source of pollutants.
Jenkins, M., Adams, M.P., Endale, D.M., Fisher, D.S., Lowrance, R.R., Newton, G.L. 2015. Storm flow dynamics and loads of fecal bacteria associated with ponds in southern piedmont and coastal plain watersheds with animal agriculture. Agricultural Water Management. 148:97-105.