2009 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 ongoing study of carbon sequestration by rangeland; the 9 years of data has been summarized. Also, the data from previous research on carbon sequestration by rangeland was 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 in FY2008, and data has been collected for two growing seasons. These 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 FY2010 to the Journal of Rangeland Ecology and Management. The evaluation of legumes as a nitrogen source study has been initiated and the two years of samples have been collected; samples for year two are currently being analyzed in the laboratory. All the data to examine the GPFARM model were transferred to cooperators in Fort Collins, CO, in FY2008. In FY09, the initial calibration runs of the climate and forage production modules of the Southern Plains GPFARM model were completed, and a manuscript has been prepared for submission in FY2010.
Forage intake is a key determinant of cattle performance: Forage intake by cattle depends not only on the nutritive value of the grass, but also its availability and accessibility, the latter being directly related to sward height. We used three tillage systems to establish wheat pastures with canopies differing in structure to evaluate effects on short-term forage intake rate and dynamics by beef steers. Forage intake rate was increased as sward surface height increased, resulting in steers that grazed the tallest pastures being most efficient. Hence, pastures with greater leaf accessibility as a result of increased sward surface height encourages grazing cattle to reach the same forage intake level in less time. Therefore, it may be logical to reduce area and time allocations in pastures with taller swards where a leafy upper canopy stratum is found.
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Gunter, S.A., Beck, P.A., Kreider, D.L., Gregorini, P., Stewart, C.B. 2009. The effects of a modified glucomannan on the performance of stocker cattle grazing endophyte infected tall fescue. Professional Animal Scientist. 25:300-306.