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Research Project: Sustaining Southern Plains Landscapes through Plant Genetics and Sound Forage-Livestock Production Systems


2019 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. During this bridging project, we will continue to 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 Report
This is the final report for 3074-21630-011-00D which terminated in May 2019 and was replaced with project 3074-21630-012-00D. Progress was made in all objectives of this project from FY18 to FY19, 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. The plants have been grazed annually since 2014 and this project has shown that commercial varieties and experimental germplasms differed significantly in their ability to tolerate close grazing. After five years of grazing, it was shown that the experimental germplasms 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 develop a diallel population of 11 sand bluestem lines; we completed all the crosses and have viable seed for most combinations. Since completion of this diallel mating, a genetic analysis has begun 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. 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. As a result, we have selected several lines of little bluestem lines with superior seed production and qualities and have established them at four locations on the Southern Great Plains from east to west, representing high (Enid, Oklahoma; Manhattan, Kansas), intermediate (Woodward, Oklahoma), and low (Knox City, Texas) rainfall areas. Objective 2 of our project was to develop preliminary data to select and breed Sudan grass that have a reduced risk of accumulating nitrates. Selected lines of Sudan germplasms were evaluated in the greenhouse in environments for their propensity to accumulate nitrates when grown in conditions that are high risk for nitrate accumulation. Several lines of Sudan grasses have been identified that resist the accumulation of nitrates under these high-risk conditions while several others were identified that acuminate extremely high levels of nitrates under those conditions. Hence, divergence selections have been made with high- and low-nitrate lines and will be evaluated in the field during the next project cycle. 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 2.5 burn cycles with delays occurring in two of the 12-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.

1. Growing degree-days accumulation and their effect on morphological stages of the maize billbug in eastern gamagrass. Growing degree-days accumulation and their effects on morphological stages of the maize billbug in eastern gamagrass. The maize bill bug feeds on eastern gamagrass causing $825,000 annually in damages to this valuable forage crop through plant mortality and production losses. The incidence of maize billbug was studied by ARS scientist in Woodward, Oklahoma, in a six-year-old stand of eastern gamagrass, and cumulative growing degree-days were calculated for the morphological stages of the pest for two years. Growing degree-days are used by farmers to predict plant and insect development rates; such as, when a plant or insect will emerge from dormancy. The adult billbug population was more abundant and distributed through the year compared to larvae and pupae. Based on growing degree-days, the 99% quantile for larvae, pupae, and adult maize billbug population was estimated between 1,396 and 1,908 cumulated growing degree-days. Very few pupae were recovered from field sampling, which may be due to its short pupation period and weekly sampling interval. Understanding the life cycle of this insect as it applies to eastern gamagrass forage and seed production will help formulate methods for more effective controls.

2. Efficacy of mineral supplementation to growing cattle grazing winter-wheat pasture in northwestern Oklahoma. Efficacy of mineral supplementation to growing cattle grazing winter-wheat pasture in northwestern Oklahoma. Supplemental feeding of grazing cattle is a powerful tool for producers and can provide positive net returns to the livestock enterprise. Wheat pasture is a unique resource to the Southern Great Plains because income is derived from both the grain crop and the cattle body weight gain by the grazing cattle. The potential profit is exceptionally good, hence many producers decline to engage in supplementation to augment cattle performance. Mineral analysis has shown that wheat herbage is deficient in calcium relative to the nutrient requirements for growing cattle. So, cattle performance may be increased by supplementing with free-choice mineral mixtures high in calcium. ARS scientists in Woodward, Oklahoma, examined the practice of providing free-choice mineral mixtures (15% to 17% calcium, 4% phosphorus, 5.5% magnesium, 18.5% to 22.0% salt, and trace minerals (1,250 ppm manganese, 650 ppm copper, 2,185 ppm zinc, 22 ppm selenium, and 65 ppm iodine)) with especially high concentrations of calcium, to compensate for the high potassium in the wheat herbage, to cattle grazing winter-wheat pasture. Cattle offered free-choice minerals in ground-style feeders had up to a 43% faster average daily body weight gain than cattle not offered minerals and at the end of the grazing period supplemented cattle weighed as much as 6% more than non-supplemented cattle. Mineral intakes averaged 4.4 ounces/day, resulting in a cost of supplement to pound of added body weight gain of $0.09 (assuming a mineral cost of $0.025/ounce). Supplementing a high-calcium, free-choice mineral mixture to cattle grazing winter-wheat pasture increases daily body weight gain and increases the net-return to the stocker cattle enterprise.

Review Publications
Dhakal, K., Springer, T.L. 2019. Growing degree-days accumulation and trends in phenological stages of the maize billbug [Sphenophorus maidis (Chittenden)] in eastern gamagrass [Tripsacum dactyloides (L.) L.]. Trends in Entomology. 14:71-77.
Mornhinweg, D.W., Armstrong, J.S., Carver, B.F., Springer, T.L. 2018. Registration of STARS 1501B and STARS 1502B barley germplasm with Rsg2 resistance to greenbug. Journal of Plant Registrations. 12(2):237-240.
Larson-Nash, S.S., Robichaud, P.R., Pierson, F.B., Moffet, C.A., Williams, C.J., Spaeth, K.E., Brown, R.E., Lewis, S.A. 2018. Recovery of small-scale infiltration and erosion after wildfires. Journal of Hydrology and Hydromechanics. 66(3):261-270.
Moffet, C., Hardegree, S.P., Abatzoglou, J.T., Hegewisch, K.C., Reuter, R., Sheley, R.L., Brunson, M.W., Flerchinger, G.N., Boehm, A.R. 2018. Weather tools for retrospective assessment of restoration outcomes. Rangeland Ecology and Management. 72(2):225-229.
Springer, T.L., Thacker, E.T. 2017. Apparent seed digestibility and germination of seeds after passage through the digestive system of northern bobwhite. Southwestern Naturalist. 62(3):193-199.
Gunter, S.A., Combs, G.F. 2019. Efficacy of mineral supplementation to growing cattle grazing winter-wheat pasture in northwestern Oklahoma. Translational Animal Science.
Hardegree, S.P., Roundy, B., Walters, C.T., Reeves, P.A., Richards, C.M., Moffet, C., Sheley, R.L., Flerchinger, G.N. 2018. Hydrothermal germination models: assessment of the wet-thermal approximation of potential field response. Crop Science. 58(5):2042-2049.