Location: Water Quality and Ecology Research
2017 Annual Report
Objectives
1. Assess and quantify ecological processes that influence water resources in agricultural ecosystems.
1a. Identify and quantify environmental factors that drive processes that are related to retention or removal of agricultural contaminants.
1b. Examine relationships between physical, chemical, and biological factors and ecological responses impacted by agriculture in the Lower Mississippi River Basin.
2. Assess and quantify the benefits of water resource management practices to enhance agricultural ecosystems.
2a. Quantify the long-term effects of conservation practices on aquatic and terrestrial resources in the Lower Mississippi River Basin.
2b. Assess the benefits and risks of management strategies and practices on soil and water resources at multiple scales.
3. Develop a watershed-scale integrated assessment of ecosystem services in agricultural landscapes of the Lower Mississippi River Basin.
3a. Develop technologies and tools to assess water and conservation management strategies in agricultural watersheds.
3b. Evaluate how ecosystem services derived from conservation practices improve water quality and ecology in agricultural watersheds.
4. As part of the LTAR network, and in concert with similar long-term, land-based research infrastructure in the Mid-South region, use the Lower Mississippi River Basin LTAR site to improve the observational capabilities and data accessibility of the LTAR network and support research to sustain or enhance agricultural production and environmental quality in agroecosystems characteristic of the Mid-South region. Research and data collection are planned and implemented based on the LTAR site application and in accordance with the responsibilities outlined in 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.
4a. Develop the Lower Mississippi River Basin LTAR location addressing issues of long-term agroecosystem sustainability specific to the region, participating in the Shared Research Strategy, and contributing to network-wide monitoring and experimentation goals.
4b. Enhance the Lower Mississippi River Basin CEAP watershed longterm data sets and integrate with other long-term data sets in the Lower Mississippi River Basin to address agroecosystem sustainability at the basin scale.
5. Increase knowledge and understanding of the processes governing movement, storage, and quality of water in the Mississippi River Valley Alluvial Aquifer, and develop technologies to enhance the sustainability of water resources for agriculture.
Approach
Many experiments described in the following involve collection and analysis of water quality samples from field sites within the Lower Mississippi River Basin (LMRB). Data acquisition (sample collection, preservation, handling, analysis, quality control), except where otherwise noted, follows standard procedures (APHA, 2005). Base flow samples are collected manually, while storm event or runoff samples are collected using automated pumping samplers (ISCO GLS Compact Composite Samplers) activated by acoustic Doppler water level and area velocity water flow sensors (ISCO 2100). All samples are placed on ice for transport to the laboratory for analysis and held in cold storage (4o C). Storm samples are retrieved within 24 h of collection. All water samples are analyzed for total and dissolved solids (drying at 105o C), total P and total Kjeldahl N (block digestion and flow injection analysis using a Lachat QuikChem® 8500 Series 2 Flow Injection Analysis System). Additional analyses conducted for certain experiments include hardness (EDTA titrimetric method) alkalinity (titration method), turbidity (calibrated Hach electronic turbidimeter); NH4-N, NO3-N, NO2-N, and soluble (filterable) P (all with the Lachat system), and chlorophyll a (pigment extraction with spectrophotometric determination).
Progress Report
Research in the Conservation Effects Assessment Program (CEAP) Beasley Lake watershed continues to assess the long-term (1996 – present) impacts of conservation practices for improvements in edge of field and lake water quality, soil health, and lake productivity. Hydrological, biological, chemical, and physical data are being collected in the lake and within the watershed. Long-term data records are being analyzed and prepared for use in modeling studies to improve simulations of conservation practices in agricultural watersheds and to link watershed and lake water quality models.
Progress is underway on a series of lab and field experiments designed to assess the physical, chemical, and biological factors that contribute to water quality improvement from vegetated ditches and wetlands. Stream mesocosms are being studied to estimate denitrification rates in both vegetated and unvegetated systems during a range of flow conditions. Denitrification measurements have also been initiated in a variety of agricultural aquatic environments in Mississippi. Experiments have also begun in wetland mesocosms with a mixture of plants to assess nutrient and pesticide removal efficiencies.
Team research on water conservation and nutrient removal via a tailwater recovery ditch and reservoir system continues into the fourth year of routine, storm, and targeted seasonal sampling. The ditch is monitored with flow sensors and automatic samplers to capture runoff flow events, and the ditch and pond are being assessed for changes in water level and water quality. Data are being processed and analyzed to construct a water budget to estimate water savings and to determine changes in nutrient loads.
An updated version of the USDA Annualized Agricultural Non-Point Source (AnnAGNPS) pollutant loading model (v5.46) has been released with improved topographic processing, enhanced prairie pothole wetland features, and integrated wetland, riparian buffer, and gully simulation technologies. This technology allows for updated simulations that account for diverse management and natural watershed conditions, while providing valuable information to aid in the effective placement of watershed conservation practices for water quality improvement. Simulation studies using the updated AnnAGNPS model have been initiated to test model functionality using long-term USDA datasets.
Unit scientists continue to cooperate and coordinate on research objectives, measurement networks, and data management system development in the Agricultural Research Service (ARS) Long-Term AgroEcosystem Research (LTAR) project. A network of eddy-covariance towers in the Lower Mississippi River Basin has been established and researchers are on schedule to implement towers at two long-term study sites, as well as both business-as-usual and aspirational long term agricultural research sites. Study design for the aspirational research plots involving a corn-soy-sorghum rotation has been developed and proposed experimental sites are in review. A data management system for lab-wide implementation has been selected to begin quality control for LTAR data.
Accomplishments
1. Agricultural conservation practices improve lake water quality in agricultural watersheds. ARS researchers in Oxford, Mississippi, have studied lake nutrient concentrations for over 20 years in Beasley Lake watershed in the Mississippi Delta as part of the Conservation Evaluation Assessment Program (CEAP). Over this time, within-field, edge-of-field, and Conservation Reserve Program (CRP) practices have been implemented within the watershed. Decreasing total phosphorus, ammonium, and nitrate concentrations in Beasley Lake coincide with the amount and location of best management practices implemented in the watershed. These results provide evidence that agricultural best management practices may improve and sustain lake and floodplain water quality in agroecosystems.
2. Wetland vegetation can reduce loads of fertilizer and pesticides in agricultural runoff and maintain ecological and economic values of water bodies. Agricultural runoff containing pesticides and excessive nutrients can damage ecosystems and harm fish, invertebrates, and other aquatic organisms. ARS researchers in Oxford, Mississippi, conducted an experiment using a series of artificial wetlands planted with two aquatic plant species, common cattail and parrot feather. The wetlands were dosed with fertilizer and permethrin insecticide to measure how well the two plant species alone or in combination could remove the nitrogen and insecticide mixture when water was either flowing or stagnant. During the flow period, the combination of two parrot feather wetlands in tandem removed fertilizer more efficiently than the combination of cattail-parrot feather wetlands. When water was stagnant, the cattail only wetland most efficiently removed fertilizer. All wetlands were equally efficient at removing insecticide. The study showed that different wetland plants alone and in combinations have different removal efficiencies for fertilizer while having the same for insecticide in water.
Review Publications
Nifong, R.L. 2017. Experimental effects of grazers on autotrophic species assemblages across a nitrate gradient in Florida springs. Aquatic Botany. doi:10.1016/j.aquabot.2017.02.010.
Huang, Y., Yasarer, L.M., Li, Z., Sturm, B.S., Zhang, Z., Guo, J., Shen, Y. 2017. Air–water CO2 and CH4 fluxes along a river–reservoir continuum: Case study in the Pengxi River, a tributary of the Yangtze River in the Three Gorges Reservoir, China. Environmental Monitoring and Assessment. 189:223. doi:10.1007/s10661-017-5926-2.
