Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: SOIL ORGANIC MATTER AND NUTRIENT CYCLING TO SUSTAIN AGRICULTURE IN THE SOUTHEASTERN USA
2009 Annual Report


1a.Objectives (from AD-416)
Generally, we are designing crop and animal management strategies based on sound biogeochemical principles, that are profitable, and have positive environmental impacts. Specifically, we are developing strategies based on experiments evaluating tillage and cover crop management, crop selection and productivity, forage quality and availability, plant genetics, grazing pressure, animal health and productivity, animal manure application, nutrient cycling, soil quality, carbon storage, and water runoff and quality.


1b.Approach (from AD-416)
To be able to simultaneously address production and environmental issues, we are taking a multidisciplinary approach to.
1)understand biogeochemical mechanisms and processes involved in water and nutrient cycles,.
2)evaluate alternative management options and.
3)develop management systems to improve the sustainability of agriculture in the region. This requires both field and laboratory investigations, including fescue toxicosis effects on animal physiology. Several field studies will give long-term perspectives and yield realistic relationships between productivity and environmental health cropping studies include:.
1)water catchments receiving poultry litter with different tillage management and.
2)cover cropping trials based on plant species and method and timing of killing. Pasture studies include.
1)evaluation of grazing pressure and organic-inorganic fertilization on soil organic C storage, nutrient runoff, and productivity and.
2)water catchments with differences in endophyte association, organic-inorganic fertilization, and presence of cattle.


3.Progress Report
Long-term field studies and soil testing evaluations continued to be investigated. These included the Water Quality Study contributing to Objective 1b, the Dawson Field Grazing Study contributing to Objective 2a, the Pasture-Crop Rotation Study contributing to Objective 3a, and Cattle and Cotton Watershed Study contributing to Objective 3b. Other field studies that were outlined in the project plan and contributed to our objectives have either been terminated (Silage Cropping Intensity Study to meet Objective 1g and Salem Road Grazing Study to meet Objective 2b) or have been redesigned to meet other objectives (nitrogen requirement of cotton under conservation tillage to meet Objective 1c, soil changes under conservation tillage of cotton and corn to meet Objective 1e, and nutrient cycling changes under conservation tillage to meet Objective 1f). Laboratory studies to meet Objective 1a and Objective 1d are continuing at various stages of development.

Soil organic carbon content under various cropping, pasture, and pasture-crop rotation systems is being determined and data are contributing significantly to a growing demand for information on how conservation agricultural systems can contribute to the mitigation of greenhouse gas emissions. Scientists involved with this research project are active in assembling original data, reviewing the literature, and synthesizing available information for technical advisors. Advice is being sought from the Chicago Climate Exchange, Georgia Carbon Sequestration Registry, Soil Science Society of America special committees, Cotton Incorporated, Grassland Carbon Working Group associated with the United Nations Food and Agriculture Organization, the World Bank, the Argentinean No-Till Farmers Association, and the USDA-NRCS Conservation Effects Assessment Program for Pasture Lands.


4.Accomplishments
1. Grazing of cover crops managed with conservation tillage may not be as detrimental to soil as often perceived. Integration of crops and livestock could provide economic benefits to producers by intensifying land use and improving resource efficiency, but how this management might affect soil compaction, water infiltration, and soil strength has not been well documented. Scientists at the USDA-Agricultural Research Service in Watkinsville, Georgia conducted a 3-year field experiment, whereby annual crops were grown following termination of perennial pasture. Conventional tillage loosened soil initially compared with no tillage, but the effect diminished with time. Grazing of cover crops had no effect on soil bulk density, perhaps because of the high soil organic matter content following perennial pasture that mitigated compaction. Soil aggregation was degraded by conventional tillage. Stability of soil aggregates was unaffected by grazing of cover crops in both tillage systems. Water infiltration was reduced with grazing of cover crops when soil water content was high. Soil strength was greater under no tillage than under conventional tillage. It was also greater under grazed than under ungrazed cover crops with conventional tillage, but not different between cover crop system with no tillage. Overall, the introduction of cattle to consume the high-quality cover crop forages did not cause substantial physical damage to the soil. Crop and cattle producers who adopt integrated crop-livestock systems are encouraged to utilize conservation tillage management techniques to help preserve surface soil organic matter and prevent deterioration of soil quality. This recommendation can be applicable to small- and medium-sized farms throughout the southeastern USA.

2. No evidence of soil organic carbon sequestration deep in the soil profile under pastures in the Piedmont. Organic carbon and nitrogen in soil are important components of maintaining soil fertility. Accumulation of organic carbon in soil is also a mechanism that helps to reduce carbon dioxide concentration in the atmosphere. Various land management systems have the potential to sequester carbon from the atmosphere through photosynthesis and subsequent storage of organic matter in soil. By providing more carbon input from photosynthesis than carbon output from decomposition soils can sequester carbon and help mitigate the greenhouse effect. Researchers at the USDA-Agricultural Research Service in Watkinsville, Georgia measured soil organic carbon and nitrogen during a 12-year period of different pasture management systems and found that sequestration of carbon and nitrogen occurred in the surface foot of soil, but not deeper. Farmers, scientists, and environmental specialists can benefit from this information to guide more effective sampling strategies and to acquire better estimates of soil carbon sequestration with cattle grazing systems. Significant sequestration of carbon in soils under pasture is possible, given that pastures occupy more than 100 million acres in the United States alone. Policy makers need this information to design effective strategies to mitigate rising carbon dioxide concentration in the atmosphere.

3. Poultry litter application and pastures can increase soil microbial diversity. Diversity of microorganisms in soil is enormous. Very little is known about how long-term agricultural land management might be affecting the composition and genetic diversity of bacteria and fungi in soil. A collaborative research effort among scientists at the University of Georgia, Mississippi State University, and USDA-Agricultural Research Service in Watkinsville, Georgia investigated the role of typical long-term land management systems on soil microbial diversity in typical soils of the Piedmont region of Georgia. Management systems were broiler litter versus inorganic fertilizer application in each of conventionally tilled cropland, hayed pasture, and grazed pasture. A forest stand planted in the mid 19th century served as a control area. Soil bacterial diversity was greater under pasture systems than under forest, suggesting that forage, fertilizer application, and cattle grazing can increase the diversity of soil microorganisms, most likely due to the increase in soil organic matter that occurs with grassland management. Conventionally tilled cropland with inorganic fertilizer had similarly low diversity of soil microorganisms like the forest. Broiler litter application had a positive influence on nutrient accumulation and soil microbial activity and diversity, regardless of whether land was in crops or pasture. Contrary to a general decline in plant and animal diversity when converting natural systems to agriculture, conservation agricultural systems with wise use of animal manures can improve soil quality by increasing the number and types of microorganisms in soil. These results have important implications for scientists in their quest to preserve global genetic diversity and for society to understand the impact of agriculture on the environment.

4. Combining laboratory indices improves prediction of nitrogen availability. Nitrogen (N) accounted for 57% of the 21 million tons of chemical fertilizer nutrients (nitrogen, phosphate, and potash) used by U.S. agriculture in 2006. Better predictions of N release from soil could reduce excessive application of N fertilizers to reduce costs and potential N loss to ground and surface waters. Researchers from several Agricultural Research Service locations, Empresa Brasileira de Pesquisa Agropecuária (Brazil’s federal agricultural research agency), and universities investigated using a combination of laboratory methods for prediction of soil N availability for a range of soils from the southern USA. Using combinations of methods that included total N and a measurement of microbial growth appeared promising for predicting potentially available N. Use of this approach by soil testing laboratories could help producers save $10 to $20 per acre in reduced fertilizer costs while reducing the amount of N fertilizer lost to ground water. This information is important for producers, soil testing laboratories, extension agents, policy makers and researchers.

5. A simple laboratory method can be used to indicate soil microbial abundance. Soil microorganisms are abundant in soil and their populations may be used as a tool to estimate the relative health and fertility of a given soil. However, estimating the number of microorganisms in soil is a difficult task. Current methods are time-consuming and laborious and often involve chemical extractions or the use of chloroform. Soils are naturally dried and rewetted by the sun and rain and through the method described in this paper we propose to mimic the drying/rewetting process in the laboratory to get a rapid and reliable method for estimating soil microorganisms. This method can provide a tool for soil testing labs to evaluate management impacts on the health of the soil.

6. Novel endophyte association of tall fescue persists and is highly productive in the Piedmont. Tall fescue is a cool-season grass widespread throughout the eastern USA. A fungus naturally infects the grass, and through its ergot alkaloid production, causes poor performance and low weight gain in animals that graze tall fescue. Grassland cattle producers in the southeastern USA have a choice of tall fescue-endophyte options: (a) poor animal performance and excellent stand persistence with wild-type endophyte infection, (b) excellent animal performance and poor stand persistence with endophyte-free infection, and (c) relatively unknown animal performance and stand persistence and substantial cost of pasture renovation using novel-endophyte infection. Scientists with the USDA-Agricultural Research Service in Watkinsville, Georgia conducted a field study for 6 years to evaluate these options under continuous grazing. Cattle gain on a yearly basis was as good with broiler litter fertilization (475 lb gain/acre) as with inorganic fertilization (499 lb gain/acre). Therefore, manure from the 6 billion broilers produced in the USA each year can be an effective fertilizer on tall fescue pastures. Cattle performance on tall fescue pastures with the novel endophyte (1.7 lb gain/day) was as good as with endophyte-free association (1.6 lb gain/day), both of which were superior as on wild-endophyte-infected tall fescue (1.2 lb gain/day). With improved cattle performance and stand persistence, novel-endophyte-infected tall fescue pastures should be recommended for the establishment of new, sustainable, cool-season pastures in the Piedmont region, and these pastures can be effectively fertilized with broiler litter. These results have important implications for the more than half million farmers in the southeastern USA, as well as the agronomic support system of farm advisors, university extension, and research scientists.

7. Models can be used to predict soil organic carbon for cropping systems in the southeastern USA. Agricultural management systems are being evaluated to improve soil quality and sequester soil organic carbon with modified decision support systems. Scientists from the USDA-Agricultural Research Service in Watkinsville, Georgia and Beltsville, Maryland, USDA-Natural Resources Conservation Service, and Texas A&M University tested the performance of a recently modified decision support system (EPIC v. 3060) against a simpler decision support tool currently used by the USDA-Natural Resources Conservation Service to identify soil management systems that contribute to improved soil quality. Management systems common to the southeastern USA such as corn/cotton/cover crop rotation systems with and without tillage were evaluated at three locations (Blackland Prairie in Texas, Coastal Plain in Alabama, and Mississippi Valley Uplands). All but one of the systems were predicted to have higher soil carbon after fifty years with the largest increases in the clay soil of the Blackland Prairie and with added dairy manure fertilizer in the sandy soil of the Coastal Plain under no tillage. Soil carbon decreased in the silt loam soil in Mississippi with conventional tillage (traditional management). No-tillage management of cotton with a wheat cover crop and other crop rotations with high-residue producing crops increased soil carbon. These results will be of great importance to land managers and policy makers for improving soil quality and reducing carbon emissions from agricultural operations in the southeastern USA although there is still a great need for field-based measurements of soil quality in conservation management systems to fully validate these tools.

8. Soil and water quality are intimately linked through surface soil organic matter. Soil and water resources are fundamental components of agriculture. Soil quality can be determined by observing the functionality of soil after being subjected to different types of management. Some key functions of soil are (a) to supply nutrients to plants, (b) to allow rainfall to penetrate soil and provide water to roots, (c) to successfully filter contaminants and nutrients from water passing through soil prior to entry into groundwater, (d) to sequester carbon dioxide from the atmosphere and store C in soil organic matter, and (e) to decompose organic matter and various man-made chemicals to avoid plant and animal toxicities. Soil organic matter is a key soil property that drives many of these important soil functions, and therefore, soil organic matter is an essential component of soil quality evaluation. Conservation agricultural management (i.e., conservation tillage, cover crops, and perennial pastures) helps to build soil organic matter. A scientist from the USDA-Agricultural Research Service in Watkinsville, Georgia reviewed the literature and summarized soil and water quality responses from various conservation agricultural systems. The concentration of surface soil organic matter provided an excellent indication of the capacity of soil to allow rainfall to penetrate soil, as well as to reduce the nutrient content of water running off of the land. A direct linkage is suggested between surface soil organic matter accumulation and the potential of conservation agricultural systems to improve water quality. This concept applies to the >100 million acres currently farmed with conservation tillage and the >100 million acres of pastureland in the USA.

9. Soil organic carbon storage with conservation agricultural systems provides environmental benefits. Increasing concentration of carbon dioxide in the atmosphere during the past few centuries has contributed to a now, well-known phenomenon, called the greenhouse effect. Soil organic carbon has historically been a source of some of this carbon dioxide resulting from accelerated decomposition of soil organic matter following cultivation of large areas of natural landscapes, including much of the United States during the past couple of centuries. Today a large source of carbon dioxide is from the burning of fossil fuels, while agricultural land potentially represents a new sink for carbon dioxide to be fixed by plants and stored in soil organic matter. Some of the important management practices contributing to this change of soil from a source to a sink have been conservation tillage and retention of crop residues on fields. This book chapter, prepared by a scientist at the USDA Agricultural Research Service in Watkinsville Georgia, summarizes the multi-faceted changes in soil organic carbon resulting from conservation tillage adoption and retention of crop residues with no tillage. A key response of soil to these conservation practices is a more highly stratified depth distribution of soil organic carbon and nitrogen fractions. Greater surface soil organic matter and retention of surface residues are not only important for mitigating greenhouse gas emissions by sequestering carbon in soil, but also for enhancing water use by crops and preventing sediment and nutrient losses from wind and water erosion. Environmental benefits of conservation tillage and residue retention in agriculture are being realized on more than 100 million acres of cropland in the United States and there is potential for even greater benefit with further adoption.

10. Grass-based farming systems are essential for soil conservation and improvement in environmental quality. For centuries, farmers relied on crop rotation to maintain or enhance crop yield. Using forage grasses and legumes in rotation with summer annual or winter annual row crops can supply nutrients to subsequent crops that can decrease the need for purchased inputs. Scientists from USDA-Agricultural Research Service in Ames, Iowa and Watkinsville, Georgia collaborated to describe how perennial forage crops can protect the soil from wind and water erosion and use nutrients more efficiently than row crops growing during a fraction of the growing season. Using perennials to establish permanent grasslands on highly erodible soil can eliminate almost all soil erosion. Crop rotations with perennial forages usually have higher soil organic matter because continuous root formation, growth, and death contribute carbon to the soil. Furthermore, land in perennial forages is not tilled, which lowers oxidation losses of soil organic matter. Organic matter inputs help increase the soil water holding capacity, which can help maintain crop growth during periods with below-average rainfall. Despite these benefits, production of perennial forages dropped in the United States during the 20th century. Reasons for this decline include the development of pesticides, the expansion of fertilizer manufacturing, and changing rations for ruminants—animals, such as cattle and sheep, with a four-chambered stomach digestive system—the primary consumers of forages. External inputs for crop production substitute for the ecological role crop rotation provides by breaking pest cycles and using forages to supply nitrogen to subsequent crops. Potentially, landscapes covered with perennial grasses and legumes can play a dominant role in stabilizing soil and water resources, provide feed for ruminants and herbivores, and contribute biomass as a source of bio-renewable energy.

11. Farming with grass can increase agricultural sustainability. Achieving sustainable agricultural landscapes in grassland environments is a broad, perhaps audacious goal, yet the need for change is undeniable. Today’s agriculture and food systems are deeply rooted in the era of cheap energy, an assumption of static climate, and the ability of entities to externalize environmental and social costs. With growing world population, increased demand on water supplies, increased vulnerability to climate extremes, and low global food stocks, it is time to rethink how to provide secure and resilient food systems and enhanced economic opportunities in rural communities. While the pressures are diverse and great, times of change present opportunities to reassess options and choose new directions. Participants in the Farming with Grass conference, set out a vision for agriculture based on sound ecological principles with economic accounting for environmental services and costs. Four grand challenges of agriculture (achieving sustainable bioenergy production, adapting to and mitigating global climate change, improving water quality and availability, and ensuring food security) are interrelated and must be addressed systematically, so that today’s solutions do not create tomorrow’s problems. Past policies have favored a few commodity crops, and disfavored producers of grasses and other perennial crops. Perennial species, incorporated into diverse agricultural systems, have great potential to enhance resilience against uncertain climate and market conditions. Additionally, by developing on-farm and rural enterprises, agriculture can help revitalize communities and provide healthy, local food options. A fundamental re-thinking of agricultural policy and practice to maintain or increase production, mitigate past environmental damage, provide healthier foods (particularly to children and the poor), and increase opportunities in rural areas is proposed.


5.Significant Activities that Support Special Target Populations
Most forage/livestock operations in the Southern Piedmont are owned by small-farm producers with gross receipts well under $250,000. We are developing conservation agricultural systems appropriate for use by these small-farm producers, including no-tillage planting, cover cropping, land application of manures, and crop-livestock integration.


6.Technology Transfer

Number of Web Sites Managed2

Review Publications
Franzluebbers, A.J. 2009. Linking soil organic carbon and environmental quality through conservation tillage and residue retention. In: Lal, R. and follett, R.F. (editors), Soil Carbon Sequestration and the Greenhouse Effect, Soil Science Society of America Special Publication Book Chapter, Number 57, 2nd edition.

Franzluebbers, A.J. 2008. Linking soil and water quality in conservation agricultural systems. Electronic Journal of Integrative Biosciences. 6:15-29.

Abrahamson Beese, D.A., Causarano, H.J., Williams, J.R., Norfleet, M.L., Franzluebbers, A.J. 2009. Predicting soil organic carbon sequestration in crop production systems of the southeastern USA with EPIC and the soil conditioning index. Journal of Soil and Water Conservation Society. 64:134-144.

Franzluebbers, A.J., Stuedemann, J.A. 2008. Soil physical responses to cattle grazing cover crops under conventional and no tillage in the Southern Piedmont USA. International Journal of Soil and Tillage Research. 100:141-153.

Franzluebbers, A.J., Stuedemann, J.A. 2008. soil-profile organic carbon and total nitrogen during 12 years of pasture management in the Southern Piedmont USA. Agriculture Ecosystems and the Environment. 129:28-36.

Haney, R.L., Franzluebbers, A.J. 2009. Soil CO2 evolution: Response from arginine additions. Applied Soil Ecology. 42(3):324-327.

Jangid, K., Williams, M.A., Franzluebbers, A.J., Sanderlin, J.S., Reeves, J.H., Jenkins, M., Endale, D.M., Coleman, D.C., Whitman, W.B. 2008. Relative impacts of land-use, management intensity and fertilization on microbial community structure in agricultural systems. Soil Biology and Biochemistry. 40:2843-2853.

Singer, J.W., Franzluebbers, A.J., Karlen, D.L. 2009. Grass-Based Farming Systems: Soil Conservation and Environmental Quality. In: Wedin, W.F., Fales, S., editors. Grasslands: Quietness and Strength for a New American Agriculture. Madison, WI: ASA. p. 121-136.

Steiner, J.L., Franzluebbers, A.J., Neely, C.L. 2009. Expanding horizons of farming with grass. In: Franzluebbers, A.J., editor. Farming with Grass: Achieving Sustainable Mixed Agricultural Landscapes. Ankeny, IA: Soil and Water Conservation Society. Available: http://www.swcs.org/en/publications/farming_with_grass/ p. 216-234.

Schomberg, H.H., Wietholter, S., Griffin, T.S., Reeves, D.W., Cabrera, M.L., Franzluebbers, A.J., Fisher, D.S., Endale, D.M., Novak, J.M., Balkcom, K.S., Raper, R.L., Kitchen, N.R., Locke, M.A., Potter, K.N., Schwartz, R.C., Truman, C.C., Tyler, D.D. 2009. Assessing indices for predicting potential N mineralization in pedogenically distinct soils under different tillage management systems. Soil Science Society of America Journal. 73(5):1575-1586.

Last Modified: 7/30/2014
Footer Content Back to Top of Page