Location: Rangeland and Pasture Research2017 Annual Report
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 of the Southern Plains mixed-grass prairie. Over the next five years, we will focus on these following objectives: Objective 1: Develop enhanced germplasm of eastern gamagrass, sand bluestem, little bluestem, and Texas bluegrass for improved forage yield, forage quality, seed yield, and stand persistence. Objective 1A: Breed eastern gamagrass cultivars with improved biomass yield and other performance traits. Objective 1B: Continue to develop a diallel population of sand bluestem from 15 diverse accessions. Objective 1C: Breed little bluestem cultivars with improved forage and seed production. Objective 1D: Breed and evaluate pure Texas bluegrass and interspecific hybrids with improved performance traits. Objective 2: Develop perennial sorghum-based, interspecific, and wide hybrids with high sugar content for livestock and biofuel production on the Southern Plains. Objective 3: Evaluate the potential for using patch-burning and supplementation strategies on rangelands to improve the productivity of stocker cattle and beef cows while enhancing other ecological services. Objective 4: Evaluate alternative grass, forb, and shrub establishment practices on degraded rangelands to restore livestock productivity and ecological services. Objective 5: Evaluate and improve native and introduced warm-season grasses for use in forage-based livestock production, and determine the environmental benefits of these grasses relative to other forages, and/or cropping options.
To identify germplasm with superior traits, expand the limits of germplasm variation by wide hybridization using interspecific and intergeneric introgression and genetic manipulation, evaluate and improve native and introduced warm-season grasses for use in forage-based livestock production, and then release superior germplasm and improved cultivars. Broad-based germplasm collections of eastern gamagrass, Texas bluegrass, little and sand bluestems are maintained at the Southern Plains Range Research Station in Woodward, OK. Further, a major resource problem is over-used rangeland, making it susceptible to erosion and weeds, also compromising other ecological services. The challenge is to develop economic, energy-efficient forage grazing systems for the Southern Plains while maintaining or improving ecological service to wildlife and society. This research will employ basic agronomic, animal performance, plant and animal physiology, genetics, cytogenetic, and molecular biology experiments.
Progress was made in all five objectives, all of which are contributing to the National Program 215, Pastures, Forages, and Rangelands Systems. Objective 1 of our project is to develop and enhance germplasm of native grasses for improved forage yield, seed yield, and stand persistence. In the first subobjective (Objective 1A), due to lack of substantial re-growth after the 2016 grazing season, cattle were not re-introduced into the gamagrass to overgraze until June 2017. A final evaluation of the plot performance is being completed in 2017. Combined harvested gamagrass seed from seed increase nurseries containing an experimental diploid sexual population and true breeding triploids was cleaned and placed in cold storage. Based on seed yield per inflorescence and germination in the greenhouse, five new triploid gamagrass hybrids were selected from a spaced plant nursery to be planted in 2018. In Subobjective 1B, we completed all crosses and have a complete diallel crossing for 11 of the 15 diverse sand bluestem accessions. Due to compatibility issues, we had limited success in making crosses with four of the accessions; hence, we did not meet the required seed numbers for the complete diallel series. Therefore, these four accessions were removed from the experiment. In Subobjective 1C, in cooperation with the USDA-NRCS, we planted regional trials in Kansas, Oklahoma, and Texas of the 21 little bluestem lines that were developed at USDA-ARS in Woodward, Oklahoma, 14 of the lines were selected for greater seed germination at a low water potential. Two cycles of recurrent selection were used to develop 14 synthetic populations. Seed germination rates after 1 selection cycle were 3.7% higher than the seeds from the seven original lines, and seed germination rates after selection cycle-2 were 16.2% higher than the selection cycle-1 populations. Selection for greater seed germination at a low water potential produces synthetic lines of little bluestem with greater stand emergence potential. In Subobjective 1D, seeds were harvested from the isolated breeder seed nursery containing D4 Texas bluegrass, an ecotype selection that has potential for use as a low input turf-grass or for winter pasture. New production plots of breeder seed from approximately ten experimental hybrids derived from crosses between Texas and Kentucky bluegrass were established. These seed producing true breeding hybrids selected at Woodward have the potential to produce an attractive turf with greater heat and drought tolerance than other cool season grasses. A materials transfer agreement was completed and seed from pure Texas D4 and the hybrids was sent to a turf-grass specialist at Oklahoma State University for further off-station testing for turf performance and resistance to pathogens not present at Woodward. In our high-risk project, Objective 2, a male sterile line of sorghum was planted on a weekly bases starting in the spring of 2017 in the greenhouse to use as a female parent in the cross with Saccharum spontaneum. Although Saccharum spontaneum did flower in 2017 in the greenhouse, the timing was not synchronized with any of the sorghum plants, so crosses were not possible. Since hybrid seed was not obtained, the opportunity for screening material for sugar content was not possible. Objective 3, the experimental pastures were grazed in winter and summer of 2016 and 2017. A section within each patch burn pasture and one broadcast burn pasture was burned in early spring this year. Hence, data were collected on body weight change of the grazing stocker cattle, forage availability and forage quality several times during the two grazing periods. During the summer grazing period, we also collected multi-spectral radiometer data, digital photography, and soil moisture data on several occasions. After cattle completed the summer grazing period, pastures were sampled for forage biomass and plant species composition. In Objective 4, we discontinued our work to evaluate alternative grass, forb, and shrub establishment practices on degraded rangelands to restore livestock productivity and ecological services. We began the experiment in FY13, but in subsequent years, did not plant the experiment due to severe drought concerns at the time of planting and the prediction of continued drought for the establishment season. We may revisit this objective when superior plant materials that germinate at a low-water potential are released for little bluestem, as are being produced in 1C. Objective 5 of our project is to evaluate and improve native and introduced warm-season grasses for use in forage-based livestock production and determine the environmental benefits of these grasses. In Subobjective 5A, progress has not been made due to the abolished position of the research agronomist/geneticist. In Subobjective 5B, preliminary analysis of the species composition inside and outside the grazing exclosures has been performed. Furthermore, the soil samples collected inside and outside the exclosures have been prepared for laboratory analysis and total carbon and nitrogen in the soil have been determined.
1. Switchgrass grown for biomass. In an eight-year experiment at USDA-ARS, Woodward, Oklahoma, Panicum virgatum, commonly known as switchgrass was harvested for biomass production. The first four years urea nitrogen was used to produce switchgrass biomass; the last four years switchgrass biomass was produced from residual nitrogen (nitrogen not used from the previous year to produce biomass or nitrogen released from decaying plant materials). Annual nitrogen fertilization of switchgrass at 80 kilograms per hectare provided for sustainable biomass yields that averaged 11.7 ± 0.4 megagrams per hectare. This level of nitrogen fertilization was least affected by environmental conditions (such as drought). Residual nitrogen sustained high biomass yields for one year after fertilization ceased. Fertilization increased the concentration of soil organic carbon an average of 1.0 milligram per gram of soil, which did not decrease after fertilization ceased. Hence, the data suggested that biomass producers could occasionally skip a year of nitrogen fertilization without detrimentally impacting the production of switchgrass biomass.
Thacker, E.T., Springer, T.L. 2016. Preference of pen-reared northern bobwhite among native plant seeds of the sand sagebrush-mixed prairie. Southwestern Naturalist. 61(4):307-311.
Galyean, M.L., Gunter, S.A. 2016. Predicting forage intake in extensive grazing systems. Journal of Animal Science. 94(6):26-43.
Gunter, S.A., Bradford, J.A., Moffet, C. 2017. Effects of mass air flow rate through an open-circuit gas quantification system when measuring carbon emissions. Journal of Animal Science. 95:475-484. doi:10.2527/jas2016.0933.
Springer, T.L., Gunter, S.A., Goldman, J.J., Moffet, C. 2016. Optimizing eastern gamagrass forage harvests using growing degree days. Agricultural Sciences. 7:710-715.
Springer, T.L., Aiken, G.E. 2015. Harvest frequency effects on white clover forage biomass, quality, and theoretical ethanol yield. Biomass and Bioenergy. 78:1-5.
Boe, A., Springer, T.L., Lee, D., Rayburn, A., Gonzalez-Hernandez, J. 2013. Underutilized grasses. In: Saja. M.C., Bhandari, H.S., and Bouton, J.H., editors. Bioenergy Feedstocks: Breeding and Genetics. Oxford, UK: John Wiley & Sons, Inc. p. 173-206
Springer, T.L. 2017. Effect of nitrogen fertilization and residual nitrogen on biomass yield of switchgrass. BioEnergy Research. 10(3): 648-656.
Beck, P.A., Gadberry, M., Stewart, C., Gray, H.C., Wistuba, T.J., Cravey, M.D., Gunter, S.A. 2017. Effects of a blended garlic and cinnamon essential oil extract with and without monensin sodium on the performance of grazing steers. Professional Animal Scientist. 33:176-185.
Springer, T.L., Wynia, R.L., Rea, G.L. 2014. Registration of 'Centennial' Sand Bluestem. Journal of Plant Registrations. 8:248-252.
Reuter, R.R., Moffet, C., Horn, G.W., Zimmerman, S., Billars, M. 2017. Technical Note: Daily variation in intake of a salt-limited supplement by grazing steers. Professional Animal Scientist. 33:372-377.
Beck, P.A., Gadberry, S., Gunter, S.A., Kegley, E.B., Jennings, J.A. 2017. Invited review: Matching forage systems with cow size and environment for sustainable cow-calf production in the southern region of the United States. Professional Animal Scientist. 33(3):289-296.