2007 Annual Report
The soil conditioning index is useful in predicting soil quality in cotton production systems. Various models are being developed and utilized by scientists and government agencies to quantify the potential for carbon storage in soil. However, testing of models is needed to verify their accuracy and reliability. A collaboration among scientists from the USDA-Agricultural Research Service in Watkinsville Georgia, USDA-Natural Resources Conservation Service, Auburn University, and Texas A&M University tested the performance of a highly technical environmental model (EPIC v. 3060) against a simple predictive model currently used by the USDA-Natural Resources Conservation Service to quantify soil management systems impact on soil quality. Several cotton management systems were evaluated at three locations (Blackland Prairie in Texas, Southern Coastal Plain in South Carolina, and Southern Piedmont in Georgia). Both models predicted low soil quality with conventional tillage production of cotton without a cover crop (traditional management), but higher soil quality with no-tillage management of cotton with winter cover crop and/or rotation with other high-residue producing crops. Although both models can be used by land managers and policy makers to evaluate soil quality on the 7 million acres of cotton in the southeastern USA, there is still an urgent need to collect field-based measurements of soil quality to fully validate and refine these tools. This project is contributing to the Soil Resource Management National Program (NP202) in Problem Area 3 (Soil carbon measurement, dynamics, and management) and Problem Area 5 (Adoption and implementation of soil and water conservation practices and systems). It also will contribute to the Global Change National Program (NP204) in Component 1 (Carbon cycle and carbon storage).
Aeration of well-drained grasslands captures more rainfall and reduces phosphorus losses. Phosphorus (P) losses from organic and inorganic (manures) fertilizers applied to pastures can contribute to eutrophication of surface waters. Management practices are needed to reduce losses of P from fertilized pastures. Scientists from USDA-ARS, J. Phil Campbell Sr., Natural Resource Conservation Service and the Univ. of Georgia worked together to determine the effectiveness of mechanical aeration to reduce overland flow, runoff and nutrient losses that contaminate surface waters. At the plot scale using simulated rainfall, aeration improved retention of rainfall and reduced nutrient losses for two fertilizer sources (inorganic fertilizer and broiler litter). At the field scale, aeration reduced runoff and dissolved P losses on well-drained soils but exacerbated P losses on poorly drained soils. Results from this study are being utilized by the Georgia P-Index Workgroup to calibrate the Georgia P-Index management coefficients for determination of site vulnerability to P losses to surface waters. The Workgroup is made up representatives from the USDA-NRCS, USDA-ARS, the University of Georgia, and the Georgia Dept. of Agriculture. This project contributes to the Soil Resource Management National Program (NP202) in Problem Area 4 (Nutrient management for crop production and environmental protection) and to the Water Resource Management National Program (NP201) in Problem Area 6 (Water quality protection systems).
Stream-side pastures with 45% or more forage cover minimize nutrient and sediment transport. Losses of phosphorus (P) and nitrogen (N) to streams and rivers from adjoining pastures contribute to eutrophication of surface water bodies. Collaborators from USDA-ARS, J. Phil Campbell Sr., Natural Resource Conservation Service, University of Georgia, and North Carolina State University used simulated rainfall studies on stream-side grassland fields fertilized with inorganic fertilizers or manures to identify management systems that retain nutrients for use by plants and animals rather than transporting them to surface waters in sediment and run-off. Inorganic fertilizer lost more total P than broiler litter while the opposite was true for N. These results support the use of different nutrient-source weighting factors in risk assessment tools such as state P-Indices, which are used in nutrient management programs. Stream-side vegetative cover of 45% or more was found to be an effective management strategy to reduce sediment, P and N losses from deposited cattle feces and urine. The results of this study are being utilized by the Georgia P-Index Workgroup to support and modify source coefficients of the Georgia P-Index for the determination of site vulnerability to P losses. They are also being utilized by the North Carolina Cooperative Extension Service to develop new best management practices (BMPs). This project contributes to the Soil Resource Management National Program (NP202) in Problem Area 4 (Nutrient management for crop production and environmental protection) and to the Water Resource Management National Program (NP201) in Problem Area 6 (Water quality protection systems).
Conservation tillage system reduces nutrient losses in run-off. Losses of phosphorus (P) and nitrogen (N) to streams and rivers from adjoining cropland contribute to eutrophication of surface water bodies. ARS scientists at J. Phil Campbell Sr. Natural Resource Conservation Center, Watkinsville, GA and Southeast Watershed Research Unit, Tifton, GA, in cooperation with University of Georgia scientists simulated rainfall at a constant- and variable-intensity on loamy sand soils managed under conservation (strip-tillage) and conventional tillage. They found that constant-intensity rainfall simulations may over estimate the amount of dissolved nutrients lost to the environment in runoff. Conservation tillage resulted in more losses of dissolved P and N than conventional tillage treatments but conservation tillage systems lost 71% less total N and 67% less total P in runoff than conventional-tillage systems. This information can be used by State Cooperative Extension Systems, USDA-NRCS, environmental consultants, and agricultural producers to promote adoption of conservation tillage as a means of improving water quality, as well as for reducing soil erosion. This project contributes to the Soil Resource Management National Program (NP202) in Problem Area 4 (Nutrient management for crop production and environmental protection) and to the Water Resource Management National Program (NP201) in Problem Area 6 (Water quality protection systems).
Spatial variation in soil organic carbon and crop yield predicted with process-based model. Computer simulation models can be useful tools to predict changes in crop yields and environmental consequences from soil management practices. However, these models need to be checked or validated against data from long-term field experiments in order to have confidence in model predictions and improve their usefulness. A collaboration among scientists from the USDA-Agricultural Research Service in Watkinsville Georgia and Auburn Alabama, Auburn University, USDA-Natural Resources Conservation Service in Temple Texas, and Joint Global Change Research Institute in College Park Maryland tested the performance of a highly technical environmental model (EPIC v. 3060) against five years of crop yield and soil data collected from a corn–cotton rotation in central Alabama. The cropping system had additional variables of dairy bedding manure and conventional and conservation tillage systems. The model accounted for 88% of the variation in corn grain and cotton lint yields during the five years. Model predictions were sensitive to landscape position. Predictions of soil organic carbon at the end of five years of the different management schemes were very reasonable, although distribution with depth and within various fractions of organic matter were not wholly adequate. This research demonstrated that EPIC modeling has challenges to overcome, but could be a reasonably accurate tool to predict yield and environmental consequences for the greater than 10 million acres of corn and cotton land in the southeastern USA. This project is contributing to the Soil Resource Management National Program (NP202) in Problem Area 3 (Soil carbon measurement, dynamics, and management). It also will contribute to the Global Change National Program (NP204) in Component 1 (Carbon cycle and carbon storage).
Modeling and remote sensing used to predict the effects of conservation management on soil organic matter in West Africa. In the drought-prone Sudan-Sahelian zone of West Africa, agricultural operations are based on relatively low-output systems, which maintain production at subsistence levels. It is getting more difficult to sustain the required food supply for its people, because of land degradation from soil erosion and nutrient mining. Scientists from the USDA Agricultural Research Service in Beltsville MD and Watkinsville GA collaborated with scientists from the University of Hawaii and Institute for Rural Economy in Mali to evaluate management systems for improving soil quality and carbon sequestration. Based on land-use classification, climate variables, soil texture, in-situ soil carbon concentrations and crop growth characteristics, the EPIC-Century model was used to project the amounts of soil carbon sequestered for the region. Under continuous conventional cultivation with minimal fertilization and no residue management, the soil top layer was continuously lost due to erosion. The combination of modeling with land use classification was used to calculate that a modest, but significantly positive amount of carbon could be sequestered with ridge tillage, increased application of fertilizers, and residue management. These findings have important implications for building soil fertility, improving human livelihoods, and sequestering atmospheric carbon throughout West Africa. This project is contributing to the Soil Resource Management National Program (NP202) in Problem Area 3 (Soil carbon measurement, dynamics, and management) and Problem Area 5 (Adoption and implementation of soil and water conservation practices and systems). It also will contribute to the Global Change National Program (NP204) in Component 1 (Carbon cycle and carbon storage).
Soil bacterial populations are altered by tall fescue-endophyte associations. With the concern over carbon dioxide emission and its connection with global warming, the United States and other nations have been interested in identifying means to enhance the removal of carbon dioxide from the atmosphere. Tall fescue with endophyte infection has been shown to enhance soil organic carbon accumulation compared to tall fescue pastures without this fungal infection. Previous research indicated that the effect on soil organic carbon from the endophyte infection may have been related to toxic compounds produced by the fungus by altering the functional capability of soil bacteria involved in decomposing plant material. Scientists at the USDA Agricultural Research Service in Watkinsville GA conducted an experiment to directly determine if endophyte infection of tall fescue altered the population and diversity of soil bacteria. Endophyte-infected tall fescue decreased the population of four bacterial groups that are involved in decomposition of plant materials, compared with uninfected tall fescue. This study has identified important groups of bacteria that were affected by endophyte-infected tall fescue and has contributed to a better understanding of the potential mechanisms for enhanced soil organic carbon sequestration. This research will be of keen interest to scientists and government agencies dealing with global warming issues, greenhouse gases, and management of agricultural activities. This project is contributing to the Soil Resource Management National Program (NP202)in Problem Area 1 (Understanding and managing soil biology and rhizosphere ecology) and Problem Area 3 (Soil carbon measurement, dynamics, and management).
Moderate grazing pressure can ensure high productivity and avoidance of pasture decline. Bermudagrass is a typical pasture grass in the southeastern USA that can be grazed by beef cattle during the summer. Despite considerable research on cattle performance from bermudagrass, a gap exists in how low and high grazing pressure might affect cattle stocking rate, performance, and production over a number of years. Scientists at the USDA Agricultural Research Service in Watkinsville GA conducted a 5-year grazing study to investigate dynamics in cattle performance and production. During the first couple of years, cattle stocking rate and cattle gain were greater under high than under low grazing pressure. However by the end of five years, stocking rate and cattle gain had become similar, suggesting that high grazing pressure had reduced pasture productivity as a result of changes in plant community composition and surface soil condition. How grazing animals can alter pasture productivity and economic return needs to be a consideration in long-term management strategies on the 46 million acres of pastureland in the southeastern USA. This research will benefit: (a) science- by improving grazing land ecological theory, (b) producers- by improving productivity, and (c) the environment- by reducing land degradation. This project is contributing to the Pasture, Forage, Turf and Rangeland Systems National Program (NP215) in Component 4 (Grazing management: Livestock production and the environment).
Abrahamson Beese, D.A., Norfleet, M.L., Causarano, H.J., Williams, J.R., Shaw, J.H., Franzluebbers, A.J. 2007. Effectiveness of the soil conditioning index as a carbon management tool in the southeastern USA based on comparison with EPIC. Journal of Soil and Water Conservation 62:94-102.
Butler, D.M., Franklin, D.H., Ranells, N.N., Poore, M.H., Green, Jr., J.T. 2006. Ground cover impacts on sediemt and phosphorus export from manured riparian pastures. Journal of Environmental Quality. 35:2178-2185.
Butler, D.M., Ranells, N.N., Franklin, D.H., Poore, M.H., Green, Jr., J.T. 2007. Ground cover impacts on nitrogen export from manured riparian buffers.Journal of Environmental Quality. 36:155-162.
Doraiswamy, P.C., McCarty, G.W., Hunt Jr, E.R., Yost, R.S., Doumbia, M., Franzluebbers, A.J. 2006. Modeling soil carbon sequestration in agricultural lands of Mali. Agricultural Systems. doi:10.1016/j.agsy.2005.09.011.
Franklin, D.H., West, L.T., Radcliffe, D.E., Hendrix, P.F. 2007. Characteristics and genesis of prefrential flow paths in a Piedmont ultisol. Soil Science Society of America Journal. 71:752-758.
Franzluebbers, A.J., Brock, B.G. 2007. Surface-soil responses to silage cropping intensity on a typic kanhapludult in the Piedmont of North Carolina. International Journal of Soil and Tillage Research. 93:126-137.
Causarano, H.J., Shaw, J.N., Franzluebbers, A.J., Reeves, D.W., Raper, R.L., Balkcom, K.S., Norfleet, M.L., Izaurralde, R.C. 2007. Simulating field-scale soil organic carbon dynamics using EPIC. Soil Science Society of America Journal. 71:1174-1185.
Potter, T.L., Truman, C.C., Bosch, D.D., Strickland, T.C., Franklin, D.H., Bednarz, C.W., Webster, T.M. 2006. Combined Effects of Constant Versus Variable Intensity Simulated Rainfall and Reduced Tillage Management on Cotton Preemergence Herbicide Runoff. Journal of Environmental Quality. 35:1894-1902.
Stuedemann, J.A., Franzluebbers, A.J. 2006. Cattle performance and production when grazing bermudagrass at two forage mass levels in the southern Piedmont. Journal of Animal Science. 85(5):1340-1350.
Franklin, D.H., Cabrera, M.L., West, L.T., Calvert, V.H., Rema, J.A. 2007. Field scale, paired watershed study: aeration to reduce runoff and phosphorus losses from grass lands fertilized with broiler litter. Journal of Environmental Quality. 36:208-215.
Franklin, D.H., Truman, C.C., Potter, T.L., Bosch, D.D., Strickland, T.C., Bendnarz, C.W. 2007. Nitrogen and phosphorus runoff losses from variable and constant intensity rainfall simulations on loamy sand under conventional and strip tillage systems. Journal of Environmental Quality. 36:846-854.