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ARS Home » Southeast Area » Tifton, Georgia » Southeast Watershed Research » Research » Research Project #441611

Research Project: Shifting the Balance of Water Resources and Interacting Agroecosystem Services Toward Sustainable Outcomes in Watersheds of the Southern Coastal Plain

Location: Southeast Watershed Research

2022 Annual Report

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.

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
This project replaced terminating project 6048-13000-027-000D, "Enhancing Water Resources, Production Efficiency and Ecosystem Services in Gulf Atlantic Coastal Plain Agricultural Watersheds." Refer to terminated project for additional information. Flow data and water quality collection and analysis efforts on the Little River Experimental (LREW), University of Georgia (UGA) Gibbs Farm, and New River (NR) watersheds (urban) continue. 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. Water samples are being collected at all sites in the LREW to relate dissolved nutrient loads and dissolved organic matter (DOM) to land-use. Bi-weekly water samples from the LREW, UGA Animal Science Farm (ASF), UGA Gibbs Farm and NR watersheds, are being analyzed for DOM optical characteristics (began in November 2016). The resulting optical data are being processed using parallel factor (PARAFAC) analysis. Existing sites at the ASF, LREW O3 sub-watershed, and LREW O sub-watershed, along with new sites at the Wilson Farm are being used to evaluate livestock impacts at the watershed scale. Automated flow monitoring, sample collection, and water quality analysis at existing sites at the ASF, LREW O3, and LREW O continues. Installation of hydrologic measurement and sampling equipment was completed at the TyTy Cooperator Farm (TCF), and Sumner Cooperator farm (SCF). Pond bathymetry at both TCF and SCF was measured to obtain information on pond storage for more accurate water balance calculations. Data continue to be collected from the meteorological station installed at the SCF. Soil cores from ASF have been processed for analysis of microbial biomass C and N, processing of the SCF cores is underway. Preparations are underway for repeat soil core collections at the ASF in 2022. Re-design of field scale plots at the UGA Gibbs (GFRP) and UGA Ponder (PFRP) farms was begun in the spring of 2018 for purposes of this project. As part of this project and our participation in the USDA Long Term Agroecosystem Research (LTAR) network, we have implemented studies to compliment ongoing research conducted at all participating LTAR locations. The PFRP plots are fully operational. Completion of the GFRP plots is anticipated by the end of 2022. Baseline hydrologic data has been collected from the PFRP plots. Electricity and flumes are being installed in late summer 2022 on the GFRP plots to enable baseline hydrology of those areas. Additional groundwater wells are being installed surrounding GFRP and PFRP plots to better document shallow water table depths. Imagery, both RGB and multi-spectral, is being collected regularly over the plots to document baseline surface conditions and plot development. Baseline soil cores will be collected at the PFRP plots in fall 2022. Data collection continues at the SEWRL LTAR meteorological and phenology stations. Eddy covariance data are being collected at two sites for quantifying the exchange rates of trace gases over natural ecosystems. Very high resolution RGB and multispectral imagery is being collected throughout the growing season at three cooperator farms for model development to scale yield measurements from field to landscape. We are utilizing landscape and watershed scale assessment models to evaluate the long-term sustainability of agricultural watersheds. Toward this goal, a framework for simulation utilizing the landscape version of the Soil and Water Assessment Tool (SWAT+) on the LREW has been established. The model will be used to quantify the impacts of conservation practices and winter covers in the LREW. A geodatabase has been designed and geophysical characterization of the watershed is being incorporated into the database. NASA Synthetic Aperture Radar (SAR) Validation: Crop fields in the southern part of the LREW were selected among a handful of sites flown in the 2019, 2020 and 2021 NASA Uninhabited Aerial Vehicle SAR AM/PM campaign. This NASA effort is in anticipation of future soil moisture and agricultural cover data products by the upcoming NASA-Indian Space Research Organization (ISRO) SAR (NISAR) mission. Synthetic aperture radar data is being compiled with locally collected soil moisture and crop attribute data provided by the LREW.

1. Validation of Remotely Sensed Soil-Water. Estimates of soil moisture across the globe are critical for prediction of climate, water balance, and crop production. Soil moisture is fundamental to agricultural management and provides critical information on hydrologic and climatic processes. The Little River Experimental Watershed (LREW) managed by ARS researchers in Tifton, Georgia, is part of a nation-wide network of core validation sites collecting continuous in-situ soil-water across large spatial areas. This network has played a crucial role in the calibration and validation of satellite based remotely sensed soil-water. In-situ data collected from this network has helped to improve the accuracy of remotely sensed soil-moisture by 40% from 2002 to 2020. The credibility of the remotely sensed data has been greatly enhanced by the testing provided by this nationwide in-situ network. The LREW provides a unique data set for the diverse Coastal Plain landscape. Soil moisture satellite products are being used to improve drought analysis. Soil moisture products from SMOS and SMAP have been used to improved flood forecasting as well. Soil moisture products are being incorporated operationally to improved continental National Weather Service Noah Models. The LREW is currently one of eight ARS watersheds conducting satellite scale soil moisture calibration and validation activities at increasingly finer scales, bringing soil moisture monitoring closer to scales relevant to field-level management.

2. Importance of Long-term data in understanding soil moisture. Soil moisture is fundamental to agricultural management and provides critical information on hydrologic and climatic processes. The validation of national and global soil moisture utilizing data collected from satellites and simulated by numerical models uses ground-based measurements for verification purposes. The ground-based measurements are often assumed stable over time, but there has been little research demonstrating the consistency of a data and their variability over time. A nationwide study including ARS researchers in Tifton, Georgia, and from several other ARS watershed locations, found that ground-based measurements were able to adequately capture a full range of soil moisture conditions within one calendar year. The incorporation of long-term soil moisture data is helping to improve national and global models of soil moisture dynamics, including drought impacts, and is encouraging for network scaling activities and validation campaigns.

Review Publications
Anderson, W.F., Knoll, J.E., Olson, D.M., Scully, B.T., Strickland, T.C., Webster, T.M. 2022. Winter legume cover effects on yields of biomass-sorghum and cotton in Georgia. Agronomy Journal. 114(2):1298-1310.
Liu, P., Bindlish, R., O'Neil, P., Fang, B., Lakshmi, V., Yang, Z., Cosh, M.H., Bongiovanni, T., Holifield Collins, C.D., Starks, P.J., Prueger, J.H., Bosch, D.D., Seyfried, M.S., Williams, M.R. 2022. Thermal hydraulic disaggregation of SMAP soil moisture over continental United States. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. 15:4072-4093.
Pisani, O., Liebert, D.P., Strickland, T.C., Coffin, A.W. 2022. Plant tissue characteristics of Miscanthus x giganteus. Scientific Data.
Williams, M.R., Welikhe, P., Bos, J.H., King, K.W., Akland, M., Augustine, D.J., Baffaut, C., Beck, G., Bierer, A.M., Bosch, D.D., Boughton, E., Brandani, C., Brooks, E., Buda, A.R., Cavigelli, M.A., Faulkner, J., Feyereisen, G.W., Fortuna, A., Gamble, J.D., Hanrahan, B.R., Hussain, M., Kohmann, M., Kovar, J.L., Lee, B., Leytem, A.B., Liebig, M.A., Line, D., Macrae, M., Moorman, T.B., Moriasi, D.N., Nelson, N., Ortega-Pieck, A., Osmond, D., Pisani, O., Ragosta, J., Reba, M.L., Saha, A., Sanchez, J., Silveira, M., Smith, D.R., Spiegal, S.A., Swain, H., Unrine, J., Webb, P., White, K.E., Wilson, H., Witthaus, L.M. 2022. P-FLUX: A phosphorus budget dataset spanning diverse agricultural production systems in the United States and Canada. Journal of Environmental Quality. 51:451–461.