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United States Department of Agriculture

Agricultural Research Service


Location: Southeast Watershed Research

2011 Annual Report

1a. Objectives (from AD-416)
1. Use remote sensing tools to develop rapid assessment procedures for soil and water resources in Coastal Plain agricultural systems. a. Evaluate tillage and residue management effects on soil carbon accretion, soil water content and associated changes in crop response. b. Remotely quantify variability in crop residue cover to better develop indices that may be used to rapidly assess conservation tillage adoption at the watershed scale. 2. Modify, test, and apply the Riparian Ecosystem Management Model (REMM) to evaluate and guide restoration and management of riparian buffers and wetlands. 3. Develop an improved GIS modeling framework for accurately quantifying soil moisture, evapotranspiration (ET), and infiltration in Coastal Plain watersheds. a. Evaluate techniques for assimilating estimates of soil-moisture at the soil surface into field and watershed scale hydrologic models. b. Improve methods for estimating evapotranspiration and infiltration within Coastal Plain watersheds. 4. Evaluate the effects of land use and surface water features on nutrient and dissolved oxygen levels in Coastal Plain watersheds.

1b. Approach (from AD-416)
OBJ.1: Direct measurements of soil and plant attributes will be related to crop yield and measurable changes in soil organic carbon accretion, soil water content, plant available water content, microbial community size, soil nitrogen, and nitrate leaching. Remotely sensed data will allow us to 1) integrate the combined effects of soil organic carbon accretion and nitrogen management via real-time, non-destructive assessments of crop response, 2) monitor crop response as a function of plant available water and nitrogen contents, and 3) refine crop coefficients for improved irrigation management and water use efficiency. OBJ.2: The Riparian Ecosystem Management Model will be modified to facilitate use for specific applications such as pesticide transport, P retention estimates, and watershed scale buffer scenario testing. Procedures will be tested for integrating modifications of REMM with watershed scale models. REMM integrations with watershed and channel process models will be tested using watershed data collected at ARS and cooperator watersheds in Georgia, Delaware, Mississippi, Maryland, and elsewhere. OBJ.3: A GIS based modeling system will be developed to simulate soil moisture conditions across the region. Based upon existing soil, climate, and vegetation data, the system will allow point, field, and watershed scale estimates of evapotranspiration, runoff, and soil moisture. It is anticipated that the system will be capable of estimating soil moisture across spatially variable fields for purposes of irrigation scheduling, as well as watersheds equivalent in size to the Little River Experimental Watershed for purposes of long term water resource planning. OBJ.4: Levels of dissolved oxygen will be correlated with other measured water quality parameters for 18 sites in the Suwannee River Basin to determine if relationships exist between dissolved oxygen and stream chemistry.

3. Progress Report
A validation of soil moisture data collected by the European Space Agency Soil Moisture and Ocean Salinity (SMOS) mission was conducted utilizing data collected from the Little River Experimental Watershed along with data sets from three additional ARS research watersheds. Results indicate the SMOS data track observations of soil moisture at each of these research watersheds fairly well. Soil moisture and streamflow data collected on the Little River Experimental Watershed were used to test drought indices obtained from remotely collected satellite data. The remotely sensed evaporative stress index (ESI) was identified as a promising drought index for characterizing streamflow and soil moisture anomalies. Cooperators at North Carolina State University (NCSU) continued cooperative research to use Riparian Ecosystem Management Model (REMM) to evaluate buffers established as part of the USDA funded North Carolina Conservation Reserve Enhancement Program. We worked with a doctoral student and his major professor to apply REMM to experimental buffers that were part of the North Carolina Conservation Reserve Enhancement Program (CREP). Calibration and validation of REMM was completed and the model was used to estimate the long-term (30 years) impact of CREP buffers.

4. Accomplishments
1. Estimation of soil moisture from remotely collected satellite data. Soil moisture products from satellite sensors have the potential to dramatically improve the accuracy and timeliness of weather, climate, and agricultural assessments and forecasts used by USDA, NOAA, and other agencies. ARS researchers at Tifton, GA, Beltsville, MD, Tucson, AZ, El Reno, OK, and Boise, ID are working cooperatively on the testing. Comparisons between estimates of soil moisture from satellite data and field data collected at the ARS Little River Experimental Watershed in Tifton, GA, indicate that the satellite based estimates of soil moisture track soil moisture trends fairly well. Additional research is being conducted to improve the methods used to relate basic satellite measurements to actual soil moisture conditions on the ground.

2. Estimation of biofuels feedstock production potentials from non-forested riparian zones and grass waterways. USDA's Regional Roadmap to Meeting the Biofuels Goals of the Renewable Fuels Standard by 2022 targets the southeastern U.S. for delivery of 49.8% of the feedstock contributions needed to meet the advanced biofuels goal of 79.5 billion liters per year. Using corporate estimates that 14,160 ha must be dedicated to feedstock production within 40 km of a 136 million liter per year biofuel conversion facility converting perennial grass feedstocks via cellulosic ethanol production, we used field trial data to estimate that between 6% to 38% of the needed acreage could be gained from riparian buffers and grassed waterways. The remaining acreage, if taken from agricultural land in the 40 km radius would be from 3% to 18% of current ag lands. The analysis suggests a potential to produce > 1.98 billion liters of ethanol per year (at 270 liters per Mg dry matter and 33 Mg ha-1 yr-1 dry matter) from riparian zones alone around 11 case study cities in the coastal plain of south Georgia. Another 814 million liters per year could come from non-prime agricultural lands (at 22 Mg ha-1 yr-1 dry matter).

Review Publications
Todd, J., Lowrance, R.R., Goovaerts, P., Vellidis, G., Pringle, C. 2010. Geostatistical Modeling of the Spatial Distribution of Sediment Oxygen Demand Within a Coastal Plain Blackwater Watershed. Geoderma. 159:53-61.

Desteven, D., Lowrance, R.R. 2011. Agricultural Conservation Practices and Wetland Ecosystem Services in a Wetland-Dominated Landscape: The Piedmont-Coastal Plain Region. Ecological Applications. 21:53-517.

Dale, V., Lowrance, R.R., Mulholland, P., Robertson, G.P. 2010. Bioenergy Sustainability at the Regional-Scale. Ecology and Society. 15(4):23. Available:

Last Modified: 2/23/2016
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