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.
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.
In Objective 1A (little bluestem improvement), 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 will soon be available to producers in the Southern Plains to add to their native grass seed mixes. In 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. Genetic and non-genetic effects on nitrate accumulation for each tissue were estimated. Researcher found that only 15% of leaf nitrate and 6% of stem nitrate variation was attributed to genetic effects. Based on these results, lowering the risk of nitrate accumulation in these forages from genetic selection will likely be more challenging than originally thought. In Objective 2A (Patch burn vs. Broadcast burn study), ARS scientists conducted 2 of the 3 burns scheduled for the year. A persistent County burn ban during the burn window delayed any burning and conditions were never ideal for the last burn to be conducted. The grazing proceeded as planned for the dormant and growing season grazing periods and animal performance data and gas exchange measurements were made for the cattle. Some preliminary analysis has been completed relative to animal performance. In Objective 2B (Weather and Climate Tool Applications) ARS scientists in Woodward, Oklahoma; Boise, Idaho; and Burns, Oregon, have utilized data from these weather tools to characterize the effects of weather on rangeland production is Southeast Oregon and two manuscripts have been prepared and submitted. These tools have also been used to evaluate elevation and aspect effects on soil microclimate and germination timing for a site in Boise, Idaho. In Objective 3A (Switchgrass fertility and soil organic carbon), all 4 start-year blocks have now been established and the last block will begin the first round of fertilization treatments this coming spring. The first round of post-treatment soils sampling was completed this year, harvest of for the 2021 growing season were completed, and very 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. In Objective 4B, the field research is still being completed and indirect calorimetry is being evaluated. The first group of calves are being evaluated now, the second set of heifers have been evaluated and bred, and gas exchange measurements of their offspring will be completed in the next year. Because this project is one year delayed due to the COVID-19 shutdown. This year was the first to evaluate offspring from the maiden heifers.
1. Released two little bluestem varieties. Grassland managers across the Southern Plains desire more warm-season grass germplasms with improved establishment. They still want these germplasms to be productive, have high quality forage, provide favorable wildlife habitat and ample soil protection, but because risk of failure is a concern when considering revegetation projects with current germplasms the establishment traits need improvement. Germination and establishment are often the critical bottle necks for warm-season native grass plantings. Germplasms selected to germinate at low water potential have greater likelihood of germinating, emerging, and ultimately establishing than similar germplasms not selected for this trait, especially in years with less favorable soil moisture conditions. Using recurrent selection techniques, ARS researchers in Woodward, Oklahoma, made little bluestem selections with forage production and quality traits similar to currently available varieties, but with superior germination and establishment. These selections have now been released as new little bluestem varieties, ‘Ahring’ and ‘Sims’. Native seed companies are growing these varieties and they will soon be available for producers in the region to use for their native grass planting.
2. Two models to describe passage of particles through a ruminant's digestive track were implemented using different software and the results are not identical, but they can be used interchangeably. The total mass and kinetics of feed particles passing through the digestive tract affects feed intake, nutrient excretion, and emissions by ruminants. Ruminant nutritionists need greater access to tools that can be used to develop these models. Use of models to calculate digesta kinetics parameters will assist managers in mitigating enteric methane emission and producing food more sustainably. We evaluated two software programs for fitting parameters to one-and two-compartment age-dependent digesta kinetic models from previously published fecal-marker concentration datasets. Model parameters and digesta kinetics estimates derived from both software programs can be used interchangeably in nutritional modelling. Two-compartment models can be more problematic to fit, but residual mean-square errors are usually smaller. Model parameters from both the one-compartment and two-compartment models can be used to derive unbiased estimates of digesta kinetics from either software program.
Boerman, N.A., Moran Lauter, A., Edwards, J.W., Scott, M.P. 2021. Variation in degree of pollen exclusion for ga1-s unilateral cross incompatibility in temperate maize breeding populations. Agrosystems, Geosciences & Environment. 4(4). https://doi.org/10.1002/agg2.20220.
Springer, T.L., Carr, B. 2022. Field establishment of little bluestem populations selected for improved laboratory seed germination in simulated dry conditions. Crop Science. 62(2):958-963. https://doi.org/10.1002/csc2.20705.
Springer, T.L., Carr, B. 2022. Registration of ‘Ahring’ little bluestem. Journal of Plant Registrations. 16(2):198-204. https://doi.org/10.1002/plr2.20200.
Springer, T.L., Moffet, C. 2022. Germination and field establishment of Indiangrass populations selected for greater laboratory seed germination in simulated dry conditions. Crop Science. https://doi.org/10.1002/csc2.20822.
Hardegree, S.P., Sheley, R.L., James, J., Reeves, P.A., Flerchinger, G.N., Moffet, C. 2022. Postplanting microclimate, germination, and emergence of perennial grasses in Wyoming big sagebrush steppe. Rangeland Ecology and Management. 84:63-74. https://doi.org/10.1016/j.rama.2022.05.008.
Gunter, S.A., Gadberry, S., Coffey, K., Moffet, C. 2022. Comparing two software programs for fitting nonlinear, one- and two-compartment age-dependent digestion models: empirical data. Animal Production Science. 62(16)1630-1638. https://doi.org/10.1071/AN21311.