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United States Department of Agriculture

Agricultural Research Service

Research Project: SOIL ORGANIC MATTER AND NUTRIENT CYCLING TO SUSTAIN AGRICULTURE IN THE SOUTHEASTERN USA
2008 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 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 these 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, and Soil Science Society of America special committees. Research 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). Research is also contributing to the Global Change National Program (NP204) in Component 1 (Carbon cycle and carbon storage), Problem Area 1 (Cropping system and tillage), Problem Area 3 (Grazinglands, CRP, and buffers), and 5 (Organic carbon transformations) and the Agricultural Systems Competitiveness and Sustainability National Program (NP216) in Component 3 (Integrated whole farm production systems), Problem 1A (Strategies and technologies needed to reduce production costs and risks of economic loss).


4.Accomplishments
1. Southeastern farm survey reveals significant soil carbon sequestration with conservation agricultural systems. A long history of tillage and soil erosion has depleted soil organic matter and subsequently degraded soil quality in the southeastern United States. Research has shown that conservation agriculture (including pasture) is able to restore soil organic matter levels, but there is a need for a broad scale evaluation to properly assess the impacts of changing agricultural practices. Scientists at Agricultural Research Service in Watkinsville Georgia and Auburn Alabama cooperated with scientists from Auburn University and the University of Asuncion Paraguay to conduct an on-farm survey of soil organic matter levels under long-term conventional tillage, conservation tillage, and pasture in 87 fields distributed within the Southern Piedmont and Coastal Plain Major Land Resource Areas of Alabama, Georgia, South Carolina, North Carolina and Virginia. Across locations, soil organic matter under pastures was 75% higher than under conventional tillage and 39% higher than under conservation tillage. Our results complement experiment-station data, and the information can be used by the Natural Resources Conservation Service, extension agents and producers to promote pasture-based systems and conservation tillage on 202 million acres in the southeastern United States. Restoration of higher soil organic matter throughout the region will result in improved soil quality, plant productivity and the potential for mitigating global warming. This research 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 is also contributing to the Global Change National Program (NP204) in Component 1 (Carbon cycle and carbon storage), Problem Area 1 (Cropping system and tillage).

2. Mixing cattle and crops can increase productivity, especially with conservation tillage. Integration of crop and livestock operations has the potential for solving many maladies facing modern agriculture by improving nutrient cycling, soil quality, and environmental quality, as well as diversifying farm income. Scientists at Agricultural Research Service in Watkinsville Georgia conducted a field experiment during four years to determine (1) the impact of grazing cattle on crop production components, (2) the choice of tillage system on crop and cattle production, and (3) how tillage and cover crop management might impact economic return. Grazing of cover crops by cattle caused a slight reduction in corn grain yield, but had no effect on wheat grain yield compared to a system with unharvested cover crops. Conservation tillage improved corn grain yield, produced greater cover crop biomass production, and contributed to greater cattle production than conventional-tillage management. Economic return followed the order: conservation tillage with grazing of cover crops > conventional tillage with grazing of cover crops > conservation or conventional tillage without grazing of cover crops. This study suggests there is great potential to improve farm-level economic stability and increase economic return on the existing 26 million acres of cropland in the southeastern United States by adopting conservation-tillage management and allowing cattle to graze cover crops. This research is contributing to the Soil Resource Management National Program (NP202) in Problem Area 5 (Adoption and implementation of soil and water conservation practices and systems) and the Agricultural Systems Competitiveness and Sustainability National Program (NP216) in Component 3 (Integrated whole farm production systems) , Problem 1A (Strategies and technologies needed to reduce production costs and risks of economic loss).

3. Soil organic matter is preserved with grazing of cover crops managed with conservation tillage. 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 organic matter and its characteristics is not known. Scientists at Agricultural Research Service in Watkinsville Georgia conducted a 3-year field experiment following termination of perennial pasture. Management systems evaluated were tillage (plow initially / disking thereafter and no tillage), cropping (sorghum or corn with rye as winter cover and winter wheat with pearl millet as summer cover), and cover cropping (grazed by cattle and left unharvested). Tillage system had the most dominating influence on soil organic matter and microbial properties. If not tilled, soil organic matter remained very high near the soil surface and remained equivalent to long-term pasture. With plowing, soil organic matter was reduced in content due to greater decomposition. Cattle grazing cover crops did not have any major negative influences on soil organic matter, and sometimes even had positive influences on soil organic matter due to faster cycling of cover crop biomass to the soil through manure. Therefore, crop and cattle producers who adopt integrated crop-livestock systems are encouraged to utilize conservation tillage management techniques to help retain soil organic matter and build soil quality. This recommendation can be applicable to small- and medium-sized farms throughout the southeastern United States. This research is contributing to the Soil Resource Management National Program (NP202) in Problem Area 5 (Adoption and implementation of soil and water conservation practices and systems), the Global Change National Program (NP204) in Component 1 (Carbon cycle and carbon storage), Problem Area 1 (Cropping system and tillage) and Problem Area 5 (Organic carbon transformations).

4. Do soils under long-term conservation tillage need loosening? Degradation of cropland with traditional inversion tillage systems has been long documented for soils in the southeastern United States. Conservation tillage systems were developed to improve soil quality for these soils. However, there is concern by producers and technical specialists that lack of mechanical soil loosening could slowly lead to soil compaction under long-term conservation tillage. Scientists at Agricultural Research Service in Watkinsville Georgia conducted a 7-year study to investigate changes in soil compaction, nutrient cycling, and soil organic carbon storage under (a) long-term no-tillage and (b) no-tillage planting with paraplowing in the autumn to loosen soil without inverting it. Immediately following paraplowing, soil was loosened without destroying soil organic matter at the soil surface. However, the high energy cost of paraplowing and the short-lived effect of paraplowing on soil loosening (soil density returned to pre-paraplowing level within 1 year), suggests that there may be little advantage to paraplowing to loosen soil. Naturally occurring soil loosening occurs with long-term conservation tillage as a result of surface residue accumulation that feeds soil organisms, thereby creating biopores for adequate root exploration of soil. This information will be valuable to producers and technical specialists across the 41 million acres of land in the Southern Piedmont region of the southeastern United States. This research 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 is also contributing to the Global Change National Program (NP204) in Component 1 (Carbon cycle and carbon storage), Problem Area 1 (Cropping system and tillage).

5. Strip-tillage systems lose less water to runoff than conventional-tillage systems. Nutrient and pesticide losses in runoff may vary between natural rainfall and rainfall simulation studies conducted by scientists. ARS scientists at J. Phil Campbell Sr. Natural Resource Conservation Center, Watkinsville, GA in cooperation with scientists at the Southeast Watershed Research Unit, Tifton, GA, and University of Georgia evaluated natural (variable) rainfall intensity patterns and constant rainfall intensity patterns on nitrogen and phosphorus losses from a loamy sand soil managed under conventional or strip tillage systems. Maximum runoff, erosion and soil carbon losses from variable-rate-simulated runoff were 1.6, 3, and 4 (respectively) times greater than from constant-rate-simulated rainfall. These results indicate that strip tillage systems may have 42% more days of crop-available water than conventional tillage and that rainfall simulators may underestimate the effectiveness of some management practices to conserve water. This information can be used by State Cooperative Extension Systems, USDA-NRCS, environmental consultants, and agricultural producers developing conservation management plans. This project is contributing to the Soil Resource Management National Program in Problem Area 4 (Nutrient management for crop production and environmental protection). It also contributes to the Water Resource Management National Program in Problem Area 6 (Water quality protection systems).

6. Counteracting land degradation with conservation agricultural systems to sequester soil carbon. Land degradation is a serious concern around the world. Conservation management practices offer an opportunity for landowners to build soil organic matter (i.e., sequester carbon in soil), while halting or reversing the effects of land degradation. Researchers at Agricultural Research Service in Watkinsville Georgia and Beltsville Maryland reviewed the literature to (1) describe carbon sequestration concepts and rationale, (2) expound on relevant management approaches to avoid land degradation and foster carbon sequestration, and (3) summarize research quantifying soil carbon sequestration. The three primary agricultural greenhouse gases (CO2, CH4, and N2O) have increased dramatically during the past century. Management practices to sequester carbon and counter land degradation include: tree planting, conservation-tillage cropping, animal manure application, green-manure cropping systems, improved grassland management, cropland-grazingland rotations, and optimal fertilization. Strategies to sequester soil carbon are urgently needed so that degraded land can be restored and further land degradation can be avoided on the 13.3 billion acres of drylands in the world. This effort 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 is also contributing to the Global Change National Program (NP204) in Component 1 (Carbon cycle and carbon storage), Problem Area 1 (Cropping system and tillage), Problem Area 3 (Grazinglands, CRP, and buffers), and Problem Area 5 (Organic carbon transformations).

7. Agricultural contributions to greenhouse gas emissions reviewed. Agriculture is a source for three primary greenhouse gases: carbon dioxide, methane, and nitrous oxide. It can also be a sink for carbon dioxide through carbon sequestration into biomass products and soil organic matter. Scientists from Agricultural Research Service in Morris Minnesota and Watkinsville Georgia summarized the literature on greenhouse gas emissions and soil carbon sequestration, providing a perspective on how agriculture can reduce its greenhouse gas burden and how it can help to mitigate greenhouse gas emissions through conservation measures. Impacts of agricultural practices and systems on greenhouse gas emission are reviewed and potential trade-offs among potential mitigation options are discussed. Conservation practices that help prevent soil erosion, may also sequester soil carbon and enhance methane consumption. Managing nitrogen to match crop needs can reduce nitrous oxide emission and avoid adverse impacts on water quality. Manipulating animal diet and manure management can reduce methane and nitrous oxide emissions from animal agriculture. All segments of agriculture have management options that can reduce agriculture’s environmental footprint. This effort 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 is also contributing to the Global Change National Program (NP204) in Component 1 (Carbon cycle and carbon storage), Problem Area 1 (Cropping system and tillage), Problem Area 3 (Grazinglands, CRP, and buffers), and Problem Area 5 (Organic carbon transformations).

8. Potential integrated crop-livestock systems reviewed for the southeastern USA. Specialization of crop and livestock operations in modern agriculture is common, but is not necessarily the most profitable, ethical, nor environmentally appropriate mode of agricultural production. There is a need to explore alternative production systems that might optimize production, profit, and environmental quality issues. A scientist at Agricultural Research Service in Watkinsville Georgia reviewed available literature to develop integrated crop-livestock production systems suitable for the southeastern United States. Rotation of crops with pasture could have benefits to both crop and livestock production systems. Growing crops in rotation with cover crops using conservation tillage would improve soil and environmental quality and increase income diversity and avoid risk, if cover crops could be grazed by cattle or other livestock. This review will assist scientists, extension specialists, and farmers to design and implement more robust agricultural systems to maintain high production, improve profit, spread investments costs across multiple operations, increase water and nutrient use efficiency, and improve environmental quality on the 100 million acres of farmland in the southeastern United States. This research is contributing to the Soil Resource Management National Program (NP202) in Problem Area 5 (Adoption and implementation of soil and water conservation practices and systems) and the Agricultural Systems Competitiveness and Sustainability National Program (NP216) in Component 3 (Integrated whole farm production systems), Problem 1A (Strategies and technologies needed to reduce production costs and risks of economic loss).

9. Reconsidering integrated crop-livestock systems in North America. Although integrated crop-livestock systems have been employed globally for millennia, in the past century, farmers in North America have tended toward increased specialization. There is renewed interest in reintegrating crops and livestock because of concerns about natural resource degradation, the profitability and stability of farm income, long-term sustainability, and increasing regulation of concentrated animal feeding operations. Scientists at Agricultural Research Service in St. Paul Minnesota and Watkinsville Georgia collaborated with a scientist from University of Manitoba in Canada to review the scientific basis for integrated crop-livestock systems in North America. Integrated crop-livestock systems could foster diverse cropping systems, including the use of perennial and legume forages, which could be grown in selected areas of the landscape to achieve multiple environmental benefits. Integrated systems inherently would utilize animal manure, which enhances soil tilth, fertility, and carbon sequestration. Integration of crops and livestock could occur within a farm or among farms, although the complexity of such systems could constrain adoption. The combination of system complexity and potential for public benefit justify the establishment of a new national or international research initiative to overcome constraints and move North American agriculture toward greater profitability and sustainability. This research is contributing to the Soil Resource Management National Program (NP202) in Problem Area 5 (Adoption and implementation of soil and water conservation practices and systems) and the Agricultural Systems Competitiveness and Sustainability National Program (NP216) in Component 3 (Integrated whole farm production systems), Problem 1A (Strategies and technologies needed to reduce production costs and risks of economic loss).


5.Significant Activities that Support Special Target Populations
Most forage/livestock operations in the Southern Piedmont are owned by small producers with gross receipts well under $250,000. These producers must often supplement their farm income with off-farm employment. Throughout the Southern Piedmont the lowest cost source of nitrogen for forage production is animal manure. However, many producers have soil phosphorus levels that restrict further manure application. Since FY 2005, a USDA-Sustainable Agriculture Research and Education grant to determine alternative forage management practices has been implemented that could (a) increase producer gross income, (b) export phosphorus from these high phosphorus-status farms, and (c) be reasonably implemented by limited-resource producers.


6.Technology Transfer

Number of Web Sites Managed2
Number of Non-Peer Reviewed Presentations and Proceedings6

Review Publications
Causarnao, H.J., Franzluebbers, A.J., Shaw, J.N., Reeves, D.W., Raper, R.L., Wood, C.W. 2008. Soil organic carbon fractions and aggregation in the Southern Piedmont and Coastal Plain. Soil Science Society of America Journal. 72:221-230.

Franzluebbers, A.J., Doraiswamy, P.C. 2007. Carbon sequestration and land degradation. In: Sivakumar, M.V.K., Ndiangui, N. (eds). Climate and Land Degradation, Springer Verlag, Berlin, Germany. p. 343-358.

Franzluebbers, A.J., Schomberg, H.H., Endale, D.M. 2007. Soil responses to paraplowing of long-term no-tillage cropland in the Southern Piedmont USA. International Journal of Soil and Tillage Research. 96:303-315.

Franzluebbers, A.J., Stuedemann, J.A. 2007. Crop and cattle responses to tillage systems for integrated crop-livestock production in the Southern Piedmont, USA. Renewable Agriculture and Food System. 22:168-180

Last Modified: 8/27/2014
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