Location: Rangeland and Pasture Research2014 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, all of which fall under National Program 215, Pastures, Forages, and Rangelands. Objective 1 is to develop enhanced germplasm of native grasses for improved forage yield, forage quality, seed yield, and stand persistence. In the first subobjective, eastern gamagrass was planted in 2012 to test different germplasms and available cultivars 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. At the time of this report, the germplasm and available cultivars had been grazed one time, but differences in preference by the cattle among the germplasm and available cultivars is readily apparent. In the second subobjective, to develop a diallel population of sand bluestem, we have continued to make progress in completing the crosses. After reducing the number of accessions to 11, we have some seeds in all 110 [(11 female parents x 11 male parents) minus the 11 parents] possible crossings (cells). Our goal is to have greater than 10 seeds in every cell. We need to increase the number of seeds in 34 cells in 2014 and 2015 to achieve this goal. In the third subobjective, we are breeding little bluestem with improved forage and seed production characteristics. In this subobjective, we have continued to narrow the little bluestem populations to meet our goals of improving forage and seed production in this species. This year, we planted 11 polycrosses; 7 populations for improved seed germination at low water potentials and 4 selected for high seed yield. The 7 populations will be selected again in 2015 for improved germination at low water potentials before field testing. We will begin selection of the 4 populations next year to also improve their seed germination at low water potentials. 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. Neither technique has currently detected the seedlings as true hybrids on the small subset tested. The potential hybrids are being transferred to the field to try to detect their hybrid status and evaluate their performance. Additional crosses using a male sterile line and sorghum and Saccharum ravennae as the pollen donor are in progress, and any resulting seeds should be available for evaluation in 2015. Objective 3 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 2013 on the rangeland. However, because of drought, this project has been delayed again until 2015 due to insufficient fuel on the site to carry a fire. Objective 4 is to evaluate alternative grass, forb, and shrub establishment practices on degraded rangelands to restore livestock productivity and ecological services. The experimental plots were laid out in 2013 and were planted to plots in mid-April of 2014. However, because of early spring drought conditions, no plants emerged by mid-June. In late June the site has received rainfall, and if it continues, we will be able to replant this experiment in April 2015. The objective of the Non Funded Cooperative Agreement between ARS and the DOE, Lawrence Berkeley National Lab, is to study carbon sequestration by pasture and cropland converted to switchgrass production for biofuels. The switchgrass pasture was established in 2010 and has significantly decreased during the last 3 years of drought. Research at the cropland site was discontinued in 2013 because drought nearly eliminated all switchgrass on the site, except for the very bottom of the drainages. Over the duration of the project (which ended May 2014), the Eddy Covariate data has been transferred to the cooperating laboratory at the University of Nebraska-Lincoln and was recently summarized in a scientific publication. Because we had measured carbon, water, and energy fluxes over cultivated cropland (winter wheat) and over lightly grazed prairie, and new switchgrass fields, we could conclude that growing-season precipitation showed the strongest control over carbon uptake by any system. The precipitation use efficiency varied between the systems: Grasses (prairie and switchgrass) needed at least 14 inches of precipitation during the growing season to become carbon sinks, while winter wheat needed only 4 inches. In summer, high temperatures increased water loss through evaporation and led to higher likelihood of dry soils. Therefore, summer-growing native prairie species and switchgrass experienced more seasonal droughts than spring-growing wheat. The reduction in carbon uptake resulted mostly from a decrease in forage production, and to a lesser extent from increased plant water use. The objective of the Non Funded Cooperative Agreement between ARS and Oklahoma State University is to develop best management practices for sustainable large-scale establishment and production of feedstocks. Oklahoma offers an abundance of opportunity for the growth of a variety of crops that can be converted into biofuels. Biofuel crops switchgrass, mixed grasses, biomass sorghum, sweet sorghum, energy cane, and energy beet were evaluated for biomass production at 5 locations in Oklahoma. The effect of environment, management (row spacing and plant population), and inputs (nitrogen) was evaluated at these locations. Results showed that maximum biomass in Oklahoma can be produced with <84 kg N per hectare. Key outcomes and accomplishments have developed best management practices for biomass production in Oklahoma, and ecosystem level water use and carbon sequestration potential of switchgrass were determined under Oklahoma conditions.
1. New sand bluestem variety established in dry soil. Under field conditions, soil moisture is often inadequate for satisfactory seedling establishment of native grasses. These dry soil conditions limit a rangeland manager's ability to reestablish native grasses after a disturbance such as drought or energy exploration. Research from the Southern Plains Range Research Station in Woodward, Oklahoma, has resulted in a variety of sand bluestem (Andropogon hallii Hack.) that has superior field emergence and plant density when planted in dry soil conditions. In cooperation with the NRCS Plant Materials Center in Knox City, Texas, and Manhattan, Kansas, as additional variety testing locations, this new variety of sand bluestem was developed by classical plant breeding techniques over three generations of selection. This new variety named 'Centennial' increases establishment success through increased seed germination under dry soil conditions. In fields using the new variety, plant density was increased by 17% compared to older unselected varieties. Therefore, selection for increased seed germination in sand bluestem has resulted in greater field emergence and higher plant density. The development of this grass variety will prove beneficial to all users attempting to establish native grasses on disturbed lands because of the greater establishment rate it will provide.
Goldman, J.J. 2013. Genetic relationships in advanced generation hybrids derived from crosses between Texas and Kentucky bluegrass using ISSR markers. American Journal of Plant Sciences. 4(12):2440-2443.
Augustine, D.J., Springer, T.L. 2013. Competition and facilitation between a native and domestic herbivore: Tradeoffs between forage quantity and quality. Ecological Applications. 23(4):850-863.
Coleman, S.W., Gunter, S.A., Sprinkle, J.E., Neel, J.P. 2014. Beef Species Symposium: Difficulties associated with predicting forage intake by grazing beef cows. Journal of Animal Science. 92:2775-2784.
Gunter, S.A., Springer, T.L., Loest, C.A., Goldman, J.J. 2014. Effect of processing method on in sacco ruminal degradability of organic matter and nitrogen from canola seeds and in vitro intestinal nitrogen digestion of the in sacco residue. Animal Production Science. 54:1030-1038.
Beck, P., Stewart, C.B., Gray, H.C., Gadberry, M.S., Gunter, S.A., Young, C., Hopkins, A.A. 2014. Using tall fescue in a complementary grazing program for spring calving beef cows in southern Arkansas. Professional Animal Scientist. 30:423-431.
Ratcliff, M.D., Kegley, E.B., Powell, J.G., Hawley, J., Lusby, K.S., Rowe, M.P., Gunter, S.A., Daniels, L.B., Hubbell, D.S. 2014. Effect of method and timing of castration on newly arrived stocker cattle. Professional Animal Scientist. 30:457-465.
Ratcliff, M.D., Kegley, E.B., Powell, J.G., Hawley, J., Lusby, K.S., Rowe, M.P., Gunter, S.A., Daniels, L.B., Hubbell, D.S. 2014. Assessment of the effect of castration upon arrival on long-term growth performance of stocker cattle. Professional Animal Scientist. 30:466-475.