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United States Department of Agriculture

Agricultural Research Service


Location: Rangeland and Pasture Research

2008 Annual Report

1a. Objectives (from AD-416)
1) Develop management and monitoring tools based on improved estimates of carbon sequestration and loss potential of Southern Plains mixed-grass prairie under alternative grazing systems. 2) Determine the interactions of season and frequency of prescribed burning and livestock grazing on ecosystem function, vegetation heterogeneity, and animal responses in the southern mixed-grass prairie. 3) Determine the impact of plant diversity (including invasive weeds) on establishment, productivity, and stability of degraded cropland and arid pastures seeded with improved native and introduced germplasm. 3.1) Evaluate the herbage production and soil responses of grass monocultures and in 2-, 4-, 8-, and 16-way mixtures of native and introduced grasses and grass-forb mixtures in pasture plantings for revegetation of marginal crop land in the Southern Plains. 3.2) Evaluate the use of legumes as a nitrogen source for grass-legume mixtures for reclaiming marginal croplands in the Southern Plains. 3.3) Develop optimum methods and timing for winter seeding of eastern gamagrass (Tripsacum dactyloides) 3.4) Develop establishment and management practices to integrate Texas bluegrass (Poa arachnifera) into Southern Plains complementary grazing systems. 4) Develop decision support tools for planning and management of forage-based livestock systems for the southern mixed-grass prairie and its associated marginal crop lands to extend seasonal forage yields and produce acceptable livestock products across wider gradients of soils and environmental conditions.

1b. Approach (from AD-416)
Major red meat production assets of the Southern Plains include temperate winter weather and a high forage production potential from a combination of rangeland, perennials established on marginal farmland, and annuals on farmland. Major natural resource problems include drought, over-used rangeland, farmland highly susceptible to erosion, weeds, difficulty in grass and forb establishment, low fertility on farmland seeded to forages, and low forage quality from late summer through winter. The challenge is to develop economic, energy-efficient grazing systems for the area while maintaining or improving the plant, soil, water, wildlife, and aesthetic resources. The overall approach is to gather information on forage production and quality, and cattle gain on native rangelands, perennial forages growing in marginal farmlands, and annual farmed forages as affected by management, climate, and soils. The information will be used to develop and test forage and grazing management strategies for red meat production systems.

3. Progress Report
Considerable progress has been made for the on going study of carbon sequestration by rangeland; the 8 years of data has been summarized. Also, the data from previous research on carbon sequestration by rangeland has been used to prepare a manuscript that has been accepted for publication in the Journal of Rangeland Ecology and Management. In the patch burning study, all treatments and locations were successfully applied and data collection has begun. The data for the examination of mixtures of grass to stabilize marginal cropland has been collected; it is currently being summarized for an article to be submitted in FY09 to the Journal of Rangeland Ecology and Management. The evaluation of legumes as a nitrogen source study has been initiated and the first year of samples have been collected; samples are currently being analyzed in the laboratory. All the data to examine the GPFARM model has been transferred to cooperators in Fort Collins, CO. In FY09, initial calibration runs of the climate and forage production modules of the Southern Plains GPFARM model should be completed. (NP 215, Components 1 and 2)

4. Accomplishments
1. Carbon sequestration project: There is considerable interest in potential effects of increasing atmospheric CO2 on global climate, and consequently in maximizing terrestrial and oceanic sinks. Attempts to balance known sources and sinks of the global carbon cycle often result in a "missing sink" of about 1,300 megatons annually. From the standpoint of carbon cycling, the more arid rangelands of the world occupy more than 50% of the earth's surface and may play an important role in the carbon cycle. We studied net ecosystem exchange of carbon on eight North American rangeland sites from 1996 to 2001. Although any site could be either a sink or source for CO2 depending on yearly weather patterns, five of the eight rangelands typically were sinks for CO2. Sagebrush steppes and Great Plains grasslands were sinks, but the Southwest sites were sources of CO2. Most rangelands were characterized by short periods of high carbon uptake (2 to 3 months) and long periods of near balance or a small loss. Our results show that native rangelands are a potentially important sink for atmospheric CO2, and maintaining the periods of active carbon uptake will be critical if we are to manage rangelands for carbon sequestration. (NP 215, Component 1)

5. Significant Activities that Support Special Target Populations

Review Publications
Springer, T.L., Gillen, R.L., McNew, R.W. 2007. Combining ability of binary mixtures of introduced, cool- and warm-season grasses and legumes. Crop Science. 47:2540-2546.

Gregorini, P., Gunter, S.A., Beck, P.A., Soder, K.J., Tamminga, S. 2008. The interaction of diurnal grazing pattern, ruminal metabolism, nutrient supply and management in cattle. Professional Animal Scientist. 24:308-318.

Svejcar, A.J., Angell, R.F., Bradford, J., Dugas, W., Emmerich, W.E., Frank, A.B., Gilmanov, T., Haferkamp, M.R., Johnson, D.A., Mayeux Jr, H.S., Mielnick, P., Morgan, J.A., Saliendra, N., Schuman, G.E., Sims, P.L., Snyder, K.A. 2008. Carbon fluxes on north american rangelands. Rangeland Ecology and Management. 61:465-474.

Last Modified: 07/20/2017
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