Location: Southeast Watershed Research
2025 Annual Report
Objectives
1. Quantify and assess the patterns, trends, and interactions among agroecosystems and landscape components and their impacts on water supply and water quality within the Little River Experimental Watershed (LREW) and in agricultural watersheds of the southeastern U.S.
1.A. Quantify the differences between water use and storage capacity among differing land use types in agricultural watersheds of the Georgia Coastal Plain.
1.B. Quantify differences in water quality as a function of land use in LREW sub-watersheds.
2. As part of the Long-Term Agroecosystem Research (LTAR) Network and a participant in the Conservation Effect Assessment Project (CEAP) effort, use GACP and other LTAR sites to quantify contrasting agroecosystem responses to “Business-As-Usual” and “Aspirational” treatments, among others, at plot, field, and farm scales.
2.A. Quantify the plot-level biophysical and hydrological responses to ASP practices as compared with BAU, that are characteristic of the GACP LTAR Network site.
2.B. Characterize and quantify the contaminants and dissolved trace gases transported from agroecosystems by surface and subsurface flow.
3. Quantitatively assess the effects of agricultural conservation practices on ecosystem services at field, landscape, and regional scales in agricultural watersheds of the southeastern US.
3.A. Characterize field level spatial and temporal variability of biophysical parameters on three farms within the LREW.
3.B. Quantify meteorological and phenological characteristics from crops under differing management practices.
4. Utilize landscape and watershed scale assessment models to improve understanding of tradeoffs among ecosystem services and evaluate the long-term sustainability of agricultural watersheds.
4.A. Estimate ecosystem services provided by GACP agricultural landscapes.
4.B. Quantify the impacts of regional cropping patterns, conservation practices and winter covers on hydrology and water quality in GACP watersheds.
4.C. Evaluate uncertainties in the regional water balance and scenarios of long-term water quality as a response to intensifying seasonal climatic extremes.
4.D. Evaluate tradeoffs in ecosystem services related to scenarios of conservation practice implementation for enhancing long-term sustainability of agricultural watersheds in the GACP region.
Approach
The goal of this project is to leverage our knowledge about the tradeoffs in ecosystem services to support stakeholder decisions about the balance of costs and benefits of conservation practice implementation. An additional goal includes contributions to the LTAR Network’s Strategic Plan by considering agroecosystem responses to sustainable intensification strategies. We do so by accounting for uncertainties in the regional water balance due to intensifying seasonal climatic extremes in order to more effectively manage ecosystem services through proper placement of conservation practices in the landscape.
The proposed research uses plot, field, landscape, and watershed observations from multiple locations in the 334 km2 Little River Experimental Watershed (LREW; centered at N31°36', W83°37') that are the basis for our long-term hydrology and natural resources research at SEWRL. Experiments are designed to evaluate processes at plot-to-landscape levels using the LREW as the basis for validating modeled outcomes from practice implementation. Each objective and sub-objective is designed to address selected spatial and temporal processes, provide information for extrapolations across scales, and/or explore novel technical approaches for characterizing ecosystems services within the LREW. Research is conducted on large plots (0.08 – 0.12 ha) at several farms in partnership with the University of Georgia, private producers’ fields (50 – 72 ha) within the LREW, and multiple collaborators.
We will compare historical observations in flow, ET, land cover, and groundwater withdrawal practices to better understand trends in the watershed. We will compare annual and seasonal means of discharge using appropriate parametric and non-parametric tests for analysis of watershed data. Rates of ET will be compared where quantifiable. Geospatial statistics and simulation models offer innovative methods for quantifying the relationships between land-use change, its driving factors and downstream effects on hydrology, nutrient loading, dissolved organic carbon chemistries, and effects of agricultural versus urban associations with water quality. As part of the LTAR Network, aspirational cropping scenarios that include biofuel feedstock production and winter cover crops will be compared to traditional (business-as-usual) systems with respect to impacts on ecosystem services (primarily C and nutrient stocks, water holding capacity, and stream flow and water quality), and profitability for producers. A long-term approach is necessary to fully evaluate the potential magnitudes of change as well as the stability of these changes. A combined approach using remote sensing and physical sampling will be used to measure changes to vegetation and crop production in relation to soil and weather conditions as affected by management practices. Regular image collection using multispectral UAS-borne sensors will occur throughout the year with flights timed to capture phenological stages in crop development. Inferences between the implemented conservation practices and the hydrologic and water quality impacts will be assessed via modeling.
Progress Report
In regards to Objective 1, research continued on the hydrology of the Little River Experimental Watershed (LREW) in the southern coastal plain of Georgia, USA, which is a benchmark watershed for USDA-ARS, participating in the USDA-ARS Conservation Effects Assessment Project (CEAP) for watersheds. The 9 streamflow and water quality monitoring stations throughout the watershed were continuously maintained and their data checked for quality and accuracy. In addition detailed water quality monitoring was carried out for three small irrigation ponds within the LREW, in response to producer and regulator concerns about algae growth and water quality used for irrigation. Data from the ponds were analyzed and the final dataset has been published in the National Agricultural Library’s Ag Data Commons repository. Additional water quality analyses are underway to evaluate and compare urbanized versus non-urbanized watersheds, and the effects of cattle use of a small watershed. The development of a data paper and two research articles evaluating the impacts of the cattle is underway.
Due to scheduled road and bridge work on Upper Ty Ty Road, Tift County requested that all equipment associated with Station B, the largest and most significant structure in the watershed, be removed. Consequently, the research structure was decommissioned, and all USDA-ARS equipment was removed from the site on January 28-29, 2025. While access to the site is still available, water samples and measurements are still being collected for continued monitoring of water quality. To increase public awareness of the Southeast Watershed Research Laboratory’s research program at Station B and the impact of its decommissioning, a workshop was held on January 15, 2025, providing stakeholders with an overview. The workshop’s theme was “essential water resources for agriculture in the southeastern US” and included a field trip to Station B and one of the ARS weather stations that provides real time soil moisture and rainfall data to local producers. Thirty-three participants were in attendance, representing a variety of stakeholder groups including federal and state agencies, university partners, non-government entities, and private landowners.
Under Objective 2, ARS researchers at Tifton, Georgia continued comparing crop rotations by varying the type and use of winter cover crops to evaluate plant health, biomass production, soil fertility, and weed pressure. Research on this Objective is related to plot level studies associated with the USDA Long-Term Agroecosystem Research (LTAR) Network at the Gulf Atlantic Coastal Plain (GACP) site. Due to the limitations of available space (i.e. land) for extensive research plots, the research is spread across two locations owned by our collaborators from the University of Georgia: the UGA Gibbs Farm (GRP) and the UGA Ponder Farm (PRP). At the GRP, ARS researchers completed baseline data collections of soils, surface and subsurface water, and biomass. The series of 9 plots at the GRP were officially synchronized with the GACP LTAR common experiment, with the first fall/winter and spring field activities within the common experiment framework. Research at the 6 plots in the PRP continued into the third year of research with the fall/winter (2024) and spring (2025) crop rotations. The 18-month baseline data collection is in the process of being developed into a series of datasets and a data paper for publication in late 2025.
Under Objective 3,research continued on soils collected from the Ty Ty Cooperator Farm (TCF) and the Ashburn Cooperator Farm (ACF). The cores are being processed, and analyses are underway. Due to significant sample backlog, the collection of additional aboveground biomass at the farms was paused in 2024. Existing samples are being processed to reduce the sample backlog.
Phenological and eddy flux data were collected as part of long-term data collections at both TCF and ACF locations. The phenological data are publicly available and contributed to the PhenoCam network (https://phenocam.nau.edu/webcam/) and are also archived with the National Agricultural Library. Eddy flux data are being collected at the same two sites for quantifying the exchange rates of trace gases over natural ecosystems. Data from 2018 through 2023 have been fully post-processed and are being organized as a dataset for publication in the National Agricultural Library’s Ag Data Commons. A peer-reviewed data descriptor paper is planned for submission in September 2025.
The LREW meteorological stations are operational and continue to provide continuous weather and soil moisture data important for producers in the area. The meteorological and streamflow data through 2021 were published through the USDA, Natural Resources Conservation Service, STEWARDS v4.0 database (https://www.nrrig.mwa.ars.usda.gov/stewards/stewards.html). Data from 2022 and 2023 data are being processed and prepared for uploading in late 2025. These datasets continue to attract attention and are utilized by scientists for multiple applications. In recent years, the SEWRL has lost several rain gauging stations due to agreements expiring with landowners who do not wish to renew them. Critical vacancies in the Unit have decreased our ability to seek out and engage with new collaborating landowners willing to work with us.
The SEWRL remote sensing and mapping group accomplished the annual survey of land cover in the LREW, as well as land cover monitoring in the Gibbs Watershed, a smaller area to the southeast of the LREW. The land cover data were archived in the SEWRL data servers and are contributing to validation datasets for researchers to evaluate the accuracy of regional and national land cover datasets and contribute to modeling of hydrology in the LREW.
Under Objective 4, research continued on spatial databases of soils, hydrography, land-cover, and land-management across the LREW have been updated. Historical land-cover data were assembled in a geodatabase and are being updated regularly. Most of the sub-objectives in Objective 4 relate to modeling work, such as SWAT modeling. Due to two critical vacancies by scientists leading these subobjectives, we are prioritizing the re-hiring of these positions.
Accomplishments
1. Coordinated development of a long-term national agricultural experiment to improve cropping systems production in the Gulf Atlantic Coastal Plain. ARS researchers in Tifton, Georgia implemented the USDA Long-Term Agroecosystem Research Network (LTAR) experimental design framework for local sites near Tifton. The Tifton location, known as the Gulf Atlantic Coastal Plain (GACP), is one of nineteen sites where regionally relevant agricultural production practices are being compared through coordinated treatments testing “aspirational” and “prevailing” practices. The experiment at the GACP involved the complex design and successful construction of 15 hydrologically isolated plots across two sites. ARS scientists also wrote and coordinated the development of LTAR Network protocols to collect and manage water, soils and vegetation samples. Scientists successfully completed a full period of baseline data collection to quantify landscape and site level characteristics of the experimental plots and are working on releasing the baseline datasets and associated data papers.
2. Provided high quality real-time meteorological, stream flow, and soil moisture to researchers and stakeholders. Estimates of water, including precipitation, surface and subsurface flows, and soil moisture are critical for prediction of climate, water balance, and crop production. The Little River Experimental Watershed (LREW) managed by ARS researchers at Tifton, Georgia, is part of a nation-wide network of core validation sites collecting continuous stream flow, rainfall and soil water information across large spatial areas. This network has played a crucial role in the calibration and validation of satellite based remotely sensed soil-water. Tremendous improvements have been made in accuracy and resolution of these remotely sensed data, documented through scientific publications utilizing data collected at the LREW and other locations within the core validation network. The credibility of the remotely sensed data has been greatly enhanced by the testing provided by this nation-wide in-situ network. The LREW continues to provide a unique data set for the diverse Coastal Plain landscape.
3. The concentration of pathogens in small irrigation ponds of southeast Georgia is related to water quality and environmental parameters. ARS researchers in Tifton Georgia, in collaboration with ARS scientists in Beltsville, Maryland and the University of Georgia, discovered that spatiotemporal patterns in cyanotoxins and Escherichia coli can occur in small irrigation and livestock ponds in southeast Georgia. The distribution of pathogens in the irrigation ponds is related to water quality parameters and environmental variables, such as wind direction. Small irrigation ponds are a common feature in agricultural landscapes of the Little River Experimental Watershed (LREW) that support agricultural water use in the region. Producers are experiencing the growth of thick algae in their irrigation ponds that create blockages in their pumping equipment. However, more studies are needed to understand the dynamics of small agricultural ponds and help local producers solve this water quality issue. These studies indicate the importance of monitoring small agricultural ponds to understand the drivers of pathogen variation within these water bodies. These results will provide necessary data for microbial water quality models.
4. Discovery and use of persistency in water quality in irrigation ponds. The quality of water in irrigation sources must be assessed to prevent the spread of contaminants and harm to human and animal health. Various irrigation water components, including microbes, toxins, heavy metals, and emerging pollutants, present a direct danger to consumer health. Concentrations of those components are highly variable across irrigation water sources and over time, which makes pollution monitoring prohibitively costly. ARS scientists from Beltsville, Maryland, and Tifton, Georgia, revealed and demonstrated persistent spatial patterns in concentrations of both pollutants and readily available water quality parameters in irrigation ponds in Georgia. They successfully applied artificial intelligence techniques to relate persistent patterns of contaminants and more easily obtainable water quality parameters. This achievement created the knowledge base for a drastic decrease in the number of water samples to evaluate the level of pollution in irrigation water sources and will be used to guide water resource managers and consultants who design and implement pollutant water quality monitoring.
Review Publications
Coffin, A.W., Pisani, O., Pisarello, K., Porter, K.M., Bosch, D.D., Strickland, T.C. 2024. The LTAR Croplands Common Experiment at the Gulf Atlantic Coastal Plain. Journal of Environmental Quality. 53(6):869-879. https://doi.org/10.1002/jeq2.20645.
Boatwright, L., Thudi, M., Sangiredday, M.R., Coffin, A.W., Tadesse, H.K., Vutla, S., Harris-Shultz, K.R., Knoll, J.E., Cuevas, H.E., Kumar, N., Soman, C., Schnable, J., Punnuri, S. 2024. GWAS analysis for plant height and stem diameter in sorghum using multiple phenotyping approaches. The Plant Phenome Journal. 7, e70008. https://doi.org/10.1002/ppj2.70008.
Smith, J.E., Widmer, A., Wolny, J.L., Dunn, L., Stocker, M.D., Hill, R.L., Pisani, O., Coffin, A.W., Pachepsky, Y.A. 2024. Persistence of microcystin in three agricultural ponds in Georgia,USA. Toxins. 16(11): Article e482. https://doi.org/10.3390/toxins16110482.
Widmer, J.A., Stocker, M.D., Strickland, T.C., Coffin, A.W., Pisani, O., Sharma, M., Pachepsky, Y.A., Dunn, L.L. 2025. Spatiotemporal trends of E. coli levels and their influences vary among ponds in the coastal plain of Georgia, USA. Journal of Environmental Quality. https://doi.org/10.1002/jeq2.70018.
Albright, A.T., Coffin, A.W., Pisani, O., Bosch, D.D., Strickland, T.C. 2025. A pilot study for water storage and carbon variability in an irrigation pond of the Southeastern Plains, USA. Journal of the American Water Resources Association. 61(3):e70026. https://doi.org/10.1111/1752-1688.70026.
Liebig, M.A., Abendroth, L.J., Robertson, G., Augustine, D.J., Boughton, E.H., Bagley, G.A., Busch, D.L., Clark, P., Coffin, A.W., Dalzell, B.J., Dell, C.J., Fortuna, A., Freidenreich, A.S., Heilman, P., Helseth, C.M., Huggins, D.R., Johnson, J.M., Khorchani, M., King, K.W., Kovar, J.L., Locke, M.A., Mirsky, S.B., Schantz, M.C., Schmer, M.R., Silveira, M.L., Smith, D.R., Soder, K.J., Spiegal, S.A., Stinner, J.H., Toledo, D.N., Williams, M.R., Krecker-Yost, J.L. 2024. The LTAR Common Experiment: Facilitating improved agricultural sustainability through coordinated cross-site research. Journal of Environmental Quality. 53(6):787-801. https://doi.org/10.1002/jeq2.20636.
Tsegaye, T., Marlen, E., Hapeman, C.J., Kleinman, P.J., Baffaut, C., Browning, D.M., Coffin, A.W., Spiegal, S.A. 2024. The Long-Term Agroecosystem Research Network: Cross-site transdisciplinary science to support a sustainable and resilient agriculture. Journal of Environmental Quality. 53(6):777-786. https://doi.org/10.1002/jeq2.20649.
Kaplan, N.E., Armendariz, G.A., Azad, S., Carlson, B.R., White, W.A., Abendroth, L.J., Coffin, A.W., Gordon, V.S., Maul, J.E., Osterholz, W.R., Sears, J.L. 2025. Five foundational tools for managing metadata from the USDA Long-Term Agroecosystem Research (LTAR) network. Journal of Environmental Quality. https://doi.org/10.1002/jeq2.70027.