Location: Rangeland and Pasture Research2018 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 four objectives of this project from FY12 to FY17, all which fall under National Program 215, Pastures, Forages, and Rangelands. Objective 1 of our project was to develop enhanced germplasm of native grasses for improved forage yield, forage quality, seed yield, and stand persistence. In the first subobjective (1A), eastern gamagrass was planted in 2012 to test three different germplasms and two different commercially available varieties for their tolerance to defoliation by grazing, which had been delayed until 2013 because of drought. During 2013 and 2014, full stand establishment was achieved, and grazing began in June of 2014. This project showed the commercial varieties and experimental germplasms differed significantly in their ability to tolerate grazing pressure. After three years of grazing, it was shown that the experimental germplasm of Gun Range and 1:8:1 had superior grazing resistance compared to the varieties of Verl and Pete and the experimental germplasm 2:16:15. The second subobjective (1B) was to develop a diallel population of 11 sand bluestem lines. We completed all the crosses and have viable seed for most combinations. After reducing the number of accessions to eleven, we have several seeds in all 110 [(11 female parents x 11 male parents) - the 11 parents] possible crossings (cells). Our goal was to have greater than 10 seeds in every cell, which was achieved. After completion of this diallel mating, a genetic analysis will be conducted that will aid in the development of superior cultivars of this extremely productive grass unique to the Southern Plains. In the third subobjective (1C), we bred little bluestem with improved forage and seed production characteristics. In this subobjective, we continued to narrow the little bluestem populations to meet our goals of improving forage and seed production in this species. Hence, we released seven little bluestem germplasm lines primarily selected for canopy morphology. With these little bluestem grasses, the germplasm lines NU-1 and NU-2 have a ‘not-upright’ (NU) canopy morphology that is characterized by a hemispherical shape and diffused culms. Lines UC-1 and UC-2 have an ‘upright-compact’ (UC) canopy morphology that is characterized by a columnar shape and erect culms, and UO-1, UO-2, and UO-3 have an ‘upright-open’ (UO) canopy morphology that is characterized by a caespitose shape with ascending culms. These lines also show resistance to leaf rust (Puccinia andropogonis), resistance to culm lodging, and tolerance to higher-pH soils. These germplasm lines will be useful for the breeding and development of new cultivars intended for many purposes, such as: wildlife habitat, livestock grazing, soil stabilization, and biomass for renewable energy. We did not plant regional trials of the advanced lines, selected for better germination at a low water potential, due to the lack of seed for planting at all locations. However, we did plant advanced lines at Woodward, Oklahoma and they are performing as expected; we expect to start planting the additional locations at Knoxville, Texas, Enid, Oklahoma, and Manhattan, Kansas in 2018. This research has shown that selection for greater germination at a low water potential produces germplasm lines with greater stand emergence and plant densities in the field. In the fourth subobjective (1D), a selection of seeds from the D4 Texas bluegrass ecotype that germinates at lower water potentials were planted in isolation nurseries and seed was harvested in April 2016. Seeds were also harvested from the original D4 isolated seed increase nursery. Seeds from promising hybrids, that are now under evaluation, were harvested from plants in the field. In Objective 2, approximately 500 seedlings were produced by interspecific and wide hybridizations of perennial sorghum-based forage plants for livestock and biofuel production, mainly from the cross using sweet sorghum 'Dale' as the male parent. At the seedling stage, a portion of the potential hybrids were screened by DNA markers and flow cytometry to detect the true hybrids, but neither technique has detected the seedlings as true hybrids. Additional crosses using a male sterile line, and Saccharum spontaneum and Saccharum ravennae as the pollen donors were made; however, these crossings failed to produce any seeds. Objective 3 in our project is to evaluate the potential for using patch-burning and supplementation to improve the productivity of cattle and enhance ecological services. The experimental plots were established in 2007 and we have completed 2.25 burn cycles with delays occurring in two of the 10-years because of drought and burn bans. With a goal to complete 4 burn cycles during this 16-year experiment, we are on schedule to complete this experiment and summarize the data in 2024. Objective 4 in our project is to evaluate alternative grass, forb, and shrub establishment practices on degraded rangelands to restore livestock productivity and ecological services. We have discontinued our work to evaluate alternative grass, forb, and shrub establishment practices on degraded rangelands to restore livestock productivity and ecological services because of severe drought concerns at time of planting and the prediction of continued drought for the establishment season. We may revisit this objective when superior plant materials are released for little bluestem from subobjective 1C.
1. Effect of nitrogen fertilization and residual nitrogen on biomass yield of switchgass. Switchgrass (Panicum virgatum) grown for biomass has been extensively researched where the annual precipitation is > 760 mm and the climate varies from humid to moist-subhumid. Research is needed for areas that receive < 700 mm of precipitation, where the climate varies from dry-subhumid to semiarid. The objectives for the ARS scientists in Woodward, Oklahoma were to determine 1) the effect of nitrogen fertilization on biomass production, 2) the effect of residual nitrogen on biomass production, 3) the nitrogen yield from harvested biomass, and 4) the concentration of soil organic carbon from switchgrass plots. Plots were fertilized annually with nitrogen at the rates of 0, 40, 80, and 120 kilograms/hectare from 2008 to 2011 and not fertilized from 2012 to 2015. The biomass yield varied with nitrogen rate by production year, and biomass yield as a function of nitrogen fertilization rate was either linear or curvilinear depending upon production year. When fertilized, the biomass yield averaged 4.4, 9.4, 11.6, and 13.2 ± 0.4 megagram/hectare for the 0, 40, 80, and 120 kilogram of nitrogen/hectare rates, respectively. Residual nitrogen sustained high biomass yields for 1 year after fertilization ceased. The nitrogen harvested in biomass varied with nitrogen rates by production year interactions (P < 0.05), and the harvested nitrogen yield as a function of nitrogen rate was linear each year. Fertilization increased the concentration of soil organic carbon an average of 1.0 ± 0.2 milligram/g of soil. The data suggest that switchgrass producers could occasionally skip a year of nitrogen fertilization without detrimentally impacting the production of switchgrass biomass.
Springer, T.L. 2017. Recurrent selection increases the seed germination of little bluestem (Schizachyrium scoparium). Euphytica. 213:279. https://doi.org/10.1007/s10681-017-2067-1.
Hardegree, S.P., Abatzoglou, J., Brunson, M., Germino, M., Hegewisch, K., Moffet, C., Pilliod, D., Roundy, B., Boehm, A.R., Brabec, M., Meredith, G. 2017. Weather-centric rangeland revegetation planning. Rangeland Ecology and Management. doi: 10.1016/j.rama.2017.07.003.
Gunter, S.A., Bradford, J.A. 2017. Technical Note: Effect of bait delivery interval in an automated head-chamber system on respiration gas estimates when cattle are grazing rangeland. Professional Animal Scientist. 33(4):490-497. https://doi.org/10.15232/pas.2016-01593.
Hardegree, S.P., Moffet, C., Walters, C.T., Sheley, R.L., Flerchinger, G.N. 2017. Hydrothermal germination models: Improving experimental efficiency by limiting data collection to the relevant hydrothermal range. Crop Science. 57(5):2753-2760. doi:10.2135/cropsci2017.02.0133.