2010 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.
Considerable progress has been made for the on going study of carbon sequestration by rangeland; the 10 years of data has been summarized. Also, the data from previous research on carbon sequestration by rangeland has been used to construct a manuscript and has been published in Global Change Biology (Objective 1). In the patch burning study, all treatments and locations were successfully applied in FY2008 and data has been collected for three growing seasons. A conference call is scheduled to review progress with cooperators (Objective 2). The data for the examination of mixtures of grass to stabilize marginal cropland has been collected; it is currently being summarized in an article to be submitted in FY2011 to the Journal of Rangeland Ecology and Management as well as a presentation at a meeting. The evaluation of legumes as a nitrogen source study has been initiated and the three years of samples have been collected; samples for year three are currently being analyzed in the laboratory (Objective 3). All the data to examine the GPFARM model has been transferred to cooperators in Fort Collins, CO in FY2008. In FY09, the climate and forage production modules of the Southern Plains GPFARM model were tested and a manuscript has been accepted for publication in the Journal of Rangeland Ecology and Management in FY2010 (Objective 4).
Yellow bluestem pastures don't benefit from prescribed burn or herbicide treatments. Yellow bluestem pastures are often burned or sprayed with herbicides annually to control weedy species, believing that the treatments will increase forage production and livestock performance. However, these are costly practices for forage producers, and they question whether there is enough benefit for the enterprise to justify the expense and environmental risk. An ARS scientist at Woodward, Oklahoma, in collaboration with Kansas State University, evaluated these practices and found that regular prescribed fire or herbicide applications in the spring are not necessary for the optimal management of Yellow bluestem pastures and do not increase livestock performance. Adequate fertilization and proper grazing management seem to be the most effective annual treatments for the management of Yellow bluestem pastures. Eliminating ineffective practices results in a substantial savings to the producers, while reducing the health and environmental impacts associated with burns and herbicide usage.
Beck, P.A., Stewart, C.B., Gunter, S.A., Singh, D. 2009. Evaluation of tall fescues for stocker cattle in the Gulf Coastal Plain. Professional Animal Scientist. 25:569-579.
Gregorini, P., Gunter, S.A., Beck, P.A., Caldwell, J., Bowman, M.T., Coblentz, W.K. 2009. Short-term foraging dynamics of cattle grazing swards with different canopy structures. Journal of Animal Science. 87:3817-3824.
Polley, H.W., Emmerich, W., Bradford, J.A., Sims, P.L., Johnson, D.A., Saliendra, N.Z., Svejcar, T., Angell, R., Frank, A.B., Phillips, R.L., Snyder, K.A., Morgan, J.A. 2010. Physiological and environmental regulation of interannual variability in CO2 exchange on rangelands in the western United States. Global Change Biology. 16:990-1002.
Polley, H.W., Emmerich, W., Bradford, J.A., Sims, P.L., Johnson, D.A., Saliendra, N.Z., Svejcar, T., Angell, R., Frank, A.B., Phillips, R.L., Snyder, K.A., Morgan, J.A., Sanabria, J., Mielnick, P.C., Dugas, W.A. 2010. Precipitation regulates the response of net ecosystem CO2 exchange to environmental variation on U.S. rangelands. Rangeland Ecology and Management. 63:176-186.
Anders, M.M., Beck, P.A., Watkins, B.K., Gunter, S.A., Lusby, K.S., Hubbell, D.S. 2010. Soil aggregates and their associated carbon and nitrogen content in winter annual pastures using different tillage management options. Soil Science Society of America Journal. 74:1339-1347.
Beck, P.A., Stewart, C.B., Gray, H.C., Smith, J.L., Gunter, S.A. 2009. Effect of wheat forage maturity and preservation method on forage chemical composition and performance of growing calves fed mixed diets. Journal of Animal Science. 87:4133-4142.