Location: Livestock, Forage and Pasture Management Research Unit
2023 Annual Report
Objectives
The vision of this research is to increase the ecological and economic sustainability of forage based livestock production systems associated with the Southern Plains mixed grass prairie. Our strategy is to minimize environmental impacts and increase the efficiency of plant and animal resources while addressing the production and conservation goals for mixed grass prairie. Over the next 5 years, we will focus on these following objectives:
Objective 1: Improve native and introduced warm-season grass establishment and resilience to biotic and abiotic stressors.
Subobjective 1A: Evaluate 21 germplasm lines of little bluestem for establishment and adaptation at 3 sites.
Subobjective 1B: Select and breed Sudan grass with reduced ability to accumulate excess nitrate from the soil with a goal of releasing a new cultivar for use in the southern Great Plains.
Objective 2: Evaluate the potential for using patch-burning and weather assessment tools on rangelands to improve the productivity of stocker cattle, while enhancing other ecological services.
Subobjective 2A: Evaluate the potential for using patch-burning on rangelands to improve the productivity of stocker cattle while enhancing other ecological services.
Subobjective 2B: Contribute and utilize weather and climate tool applications through the Long-term Agroecosystem Research (LTAR) Climate Group for national and regional LTAR agricultural and natural resource modeling programs in grazing management, ecosystem monitoring and remote sensing, soil productivity, hydrology and erosion and evaluate, develop and implement landscape-scale applications for weather and climate related rangeland planning and management needs.
Objective 3: Determine the effects of weather, timing, and the amount of nitrogen (N) fertilization applied to forage grasses either through inorganic or organic N sources and their effect on ecological services.
Subobjective 3A: Determine the effects of the amount and timing of N fertilizer application on dormant season harvested switchgrass biomass production and changes in soil organic carbon stocks.
Subobjective 3B: Determine the utility value of underseeding red clover as an N fixer for winter-wheat pasture production to replace inorganic N from fertilizer.
Objective 4: Determine genetic, annual and seasonal effects on methane emission by grazing stocker cattle.
Subobjective 4A: Evaluation of new technologies in indirect calorimetry for grazing beef cattle.
Subobjective 4B: Gas flux by calves from dams identified as either high or low methane emitters.
Approach
The research described herein provides essential knowledge to enhance the production and conservation goals for Southern Plains agroecosystems. The Southern Plains mixed-grass prairie is one of the United States' most important crop and livestock-producing regions that supports many rural communities and provides habitat for a host of plants and animals. The region’s agricultural enterprises are challenged with uncertainties in profitability, reliance on unsustainable land use practices, and an ever-increasing concern for the environment. Specifically, this project will 1) improve native and introduced warm-season grass establishment and resilience to biotic and abiotic stressors, 2) evaluate the potential for using patch-burning and weather assessment tools on rangelands to improve the productivity of stocker cattle, while enhancing other ecosystem services, 3) determine the effects of weather, timing, and the amount of nitrogen fertilization when applied to cool-season annual or warm-season perennial forage grasses either through inorganic or organic nitrogen sources and their effect on ecological services, and 4) determine genetic, seasonal and annual effects on methane emission by grazing stocker cattle. Experiments will concentrate on breeding and selecting new perennial forages and the effects of livestock grazing, prescribed fire, and soil disturbances on vegetation composition, diversity, production, and vegetation heterogeneity and animal body weight (BW) gains. Coordinated experimentation will leverage interdisciplinary work of 4 scientists to address integration of forage-livestock systems through new forages, use of patch burning and livestock grazing management to support sustainable and economically viable agricultural enterprises.
Progress Report
Objective 1A (little bluestem improvement), has been accomplished and recurrent selection for germination at low water potential was shown to improve the likelihood of establishing this species in the field. This research has resulted in the release of 2 new little bluestem varieties that are available to producers to add to their native grass seed mixes. Objective 1B (sudan grass with reduced ability to accumulate nitrate), following on previous work that identified candidate low-nitrate accumulating lines from sudan grass populations grown under high-nitrate conditions and tested for nitrate accumulation. Twenty sorghum female inbred lines and two sudan grass male populations were grown under high nitrate conditions during two growing seasons. Nitrate concentration was measured from dried leaf and stem tissue and found that genetic variance composed most of the phenotypic variance in stem and leaf tissue and concluded that sufficient genetic variance exists for developing male sterile sorghum inbred lines having leaf nitrate concentrations below the potentially lethal toxicity threshold. In Objective 2A (patch burn vs. broadcast burn study), ARS scientists conducted all 4 burns scheduled for the year. The grazing proceeded as planned for the dormant and growing season grazing periods and animal performance data were collected for the cattle. In Objective 3A (Switchgrass fertility and soil organic carbon) all 4 start-year blocks have now been established and the last block began the first round of fertilization treatments this spring. Soil for the 1st round of post treatment sampling has been completed for the 2nd year-start block, harvest for the 2022 growing season was completed, and preliminary results produced, but the long-term nature of some treatments (e.g., fertilizer applications every 3rd year) will make any interpretation of preliminary results premature. In Objective 4A (new technologies in indirect calorimetry), the measurement data have been collected, analyzed and a manuscript has been submitted and is currently in review. In Objective 4B, the field research is still being completed and gas fluxes are being evaluated. The second group of calves are being evaluated now, the third set of heifers have been evaluated and bred and gas exchange measurements of their offspring will be completed in the next year. Preliminary results indicate that methane emissions from heifers are associated with that of their dam.
Accomplishments
Review Publications
Boerman, N.A., Moffet, C., Gunter, S.A. 2023. Is it feasible to improve stand persistence of eastern gamagrass (Tripsacum dactyloides L.) through breeding? Agrosystems, Geosciences & Environment. 6(1). https://doi.org/10.1002/agg2.20335.
Boerman, N.A., Gillen, R.L., Masters, R.A. 2022. Establishment of sand bluestem with the aid of pre-emergence-applied herbicides. Crop, Forage & Turfgrass Management. 9(1). Article e20198. https://doi.org/10.1002/cft2.20198.
Wilmer, H.N., McGranahan, D.A., Moffet, C., Taylor, J.B. 2023. Effect of burn season and grazing deferment on mountain big sagebrush plant communities. Plant Ecology. 224:501-512. https://doi.org/10.1007/s11258-023-01317-1.
Goncalves Dos Santos, L., Verzegnazzi, A.L., Edwards, J.W., Frei, U.K., Boerman, N.A., Tenello Zuffo, L., Pires, L.M., De La Fuente, G.N., Lubberstedt, T. 2022. Usefulness of temperate-adapted maize lines developed by doubled haploid and single-seed descent methods. Journal of Theoretical and Applied Genetics. 135:1829-1841. https://doi.org/10.1007/s00122-022-04075-2.
Copeland, S.M., Davies, K.W., Hardegree, S.P., Moffet, C., Bates, J.D. 2022. Influence of weather on production dynamics in Wyoming big sagebrush steppe across plant associations. Rangeland Ecology and Management. 85:48-55. https://doi.org/10.1016/j.rama.2022.09.002.
Hardegree, S.P., Boehm, A.R., Glenn, N., Sheley, R.L., Reeves, P.A., Pastick, N., Hojjati, A., Boyte, S., Enterkine, J., Moffet, C., Flerchinger, G.N. 2022. Elevation and aspect effects on soil microclimate and the germination timing of fall-planted seeds. Rangeland Ecology and Management. 85:15-27. https://doi.org/10.1016/j.rama.2022.08.003.
Ralston, S.R., Rooney, W.L., Boerman, N.A. 2023. Estimating reliability for evaluating nitrate accumulation in sorghum (Sorghum bicolor L. Moench) inbred A-lines. Crop Science. 6(3). Article e20403. https://doi.org/10.1002/agg2.20403.
Springer, T.L., Brandon, C. 2022. Registration of ‘Sims’ little bluestem. Journal of Plant Registrations. 17(1):34-39. https://doi.org/10.1002/plr2.20246.
