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United States Department of Agriculture

Agricultural Research Service

Research Project: SUSTAINING AND ENHANCING SOUTHERN PLAINS RANGELAND AND PASTURE LANDSCAPES
2012 Annual Report


1a.Objectives (from AD-416):
1) Develop management and monitoring tools based on improved estimates of carbon sequestration and loss potential of Southern Plains mixed-grass prairie under alternative grazing systems. 2) Determine the interactions of season and frequency of prescribed burning and livestock grazing on ecosystem function, vegetation heterogeneity, and animal responses in the southern mixed-grass prairie. 3) Determine the impact of plant diversity (including invasive weeds) on establishment, productivity, and stability of degraded cropland and arid pastures seeded with improved native and introduced germplasm. 3.1) Evaluate the herbage production and soil responses of grass monocultures and in 2-, 4-, 8-, and 16-way mixtures of native and introduced grasses and grass-forb mixtures in pasture plantings for revegetation of marginal crop land in the Southern Plains. 3.2) Evaluate the use of legumes as a nitrogen source for grass-legume mixtures for reclaiming marginal croplands in the Southern Plains. 3.3) Develop optimum methods and timing for winter seeding of eastern gamagrass (Tripsacum dactyloides) 3.4) Develop establishment and management practices to integrate Texas bluegrass (Poa arachnifera) into Southern Plains complementary grazing systems. 4) Develop decision support tools for planning and management of forage-based livestock systems for the southern mixed-grass prairie and its associated marginal crop lands to extend seasonal forage yields and produce acceptable livestock products across wider gradients of soils and environmental conditions.


1b.Approach (from AD-416):
Major red meat production assets of the Southern Plains include temperate winter weather and a high forage production potential from a combination of rangeland, perennials established on marginal farmland, and annuals on farmland. Major natural resource problems include drought, over-used rangeland, farmland highly susceptible to erosion, weeds, difficulty in grass and forb establishment, low fertility on farmland seeded to forages, and low forage quality from late summer through winter. The challenge is to develop economic, energy-efficient grazing systems for the area while maintaining or improving the plant, soil, water, wildlife, and aesthetic resources. The overall approach is to gather information on forage production and quality, and cattle gain on native rangelands, perennial forages growing in marginal farmlands, and annual farmed forages as affected by management, climate, and soils. The information will be used to develop and test forage and grazing management strategies for red meat production systems.


3.Progress Report:
This is the final report for Project 6216-21630-008-00D, Sustaining and Enhancing Southern Plains Rangeland and Pasture Landscapes, ending in November 2012. Carbon sequestration by sand-sagebrush rangeland was quantified at both moderate and high stocking rates. This data set includes 10 years of production. These data show that high stocking rates result in carbon release, whereas moderate stocking results in this rangeland type being a carbon sink. Patch burning of re-seeded rangelands was evaluated as a tool to restore ecological services so they will function similar to native rangelands. Cattle performance, vegetation structure, or net primary production did not differ between pastures-burned every 4 years and patch burning where 25% of the pasture was burned every year. This project is scheduled to continue until 2018 so that changes in rangeland vegetation structure and function may differentiate between the systems. Herbage production of grass monocultures in 2-, 4-, 8-, and 16-way combinations of native introduced grasses and grass-forb mixtures were evaluated over a 3-year period after being established on crop land. Researchers have proposed that combinations of grass would be more productive than monocultures. However, regardless of species combination, the net primary production was similar among combinations and monocultures. Legumes were tested as a nitrogen source (NS) for grass-legume mixtures to reclaim marginal cropland on the Southern Plains. Seven NS were evaluated in three different grass species. These grasses, Sand bluestem, Yellow bluestem, and switchgrass, responded differently to legumes as a NS. In this 5-year period, Sand bluestem is the only grass that responded positively to legumes as a NS, with Hairy vetch being the most effective. Improved methods for the seeding of eastern gamagrass were developed for winter-based seeding. No-till seeding into glyphosate-killed wheat fields produced good seed germination the next spring when soil moisture was ample and temperatures were cold during the dormancy period, December to April. If dormancy breaking conditions (DBC) were not adequate the first year, then a portion of the seed would geminate and establish the second year. However, if an inappropriate DBC occurred the third year, a stand would not establish. The use of Texas bluegrass has been severely limited because the extremely cottony seed head makes it difficult to harvest and clean. Combining the use of a Woodward flail-vac seed harvester, a hammer mill, and the Woodward 2000 chaffy-seed cleaner, viable Texas bluegrass seeds were successfully planted with a no-till drill. A decision tool for planning and management of forage-based livestock systems was developed for the southern mixed-grass prairie and associated marginal farmlands. Findings show that forage growth may be affected by stocking rate and that high stocking rates lead to soil compaction, which could also affect forage growth because of limitations in soil hydrology and root penetration. Reduced forage growth under high stocking rates are predicted by the decision support tool when it was calibrated for changes in soil compaction.


4.Accomplishments
1. Texas bluegrass can now be planted with a drill. In rangeland restoration, many native grass pastures are in need of a perennial cool-season grass to complement the warm-season grasses. Texas bluegrass is one of only a few native, cool-season grasses that perenniate on the Southern Plains. The use of Texas bluegrass has been severely limited because the extremely cottony seed is difficult to harvest and clean so that it will flow through drills. An ARS scientist at Woodward, Oklahoma, discovered that by combining the use of a Flail-Vac harvester, a hammer mill, and the Woodward WW2000 Cleaner, Texas bluegrass seeds could be successfully harvested, cleaned, and planted with a commercially available no-till drill. The cleaning method will enable more widespread use of Texas bluegrass in native grass-seed mixtures for rangeland restoration.

2. Sand sagebrush removal increases livestock production on mixed-grass prairie. Sand sagebrush on native rangelands is often controlled with herbicides to enhance grass production and livestock carrying capacity. To evaluate the effects of sand sagebrush control in native rangelands on cattle performance, pastures were selected by an ARS scientist at Woodward, Oklahoma, and categorized into 3 sagebrush cover levels:.
1)high (27% cover),.
2)medium (10% cover), and.
3)low (5% cover). For 5 years, pastures were stocked annually with steers in late January and grazed until mid-August. The high, medium, and low pastures were stocked at 19, 28, and 28 animal-unit-days/acres, respectively. Body weight gain and net return per acre were greatest for low pastures (224 lb, $50) compared with high (147 lb, $36) or medium (178 pounds, $40) pastures. These results suggest that increased levels of sagebrush control, coupled with appropriate adjustments in stocking rates, are most profitable to stocker cattle production; but extensive removal of sagebrush will limit other ecological services that rangeland provides to wildlife.

3. Applying glyphosate on bermudagrass improves winter-annual grass establishment when interseeding. Attempts to inter-seed and establish wheat and annual ryegrass in bermudagrass pastures are challenging because bermudagrass is still actively growing when it is optimal to establish this pasture. Research conducted by an ARS Scientist at Woodward, Oklahoma, determined the effect of a pre-plant application of glyphosate and planting date on annual ryegrass and wheat. Pastures were planted in mid-September or mid-October using a no-till drill with and without an application of glyphosate. Pastures planted in September with glyphosate application produced 44 more grazing days per acre, 145 pounds more gain per acre, and $222 greater net returns per acre than pastures planted in September without glyphosate application or ones planted in October. Earlier plantings, along with reduced competition of warm-season grasses by spraying with glyphosate, can increase the net returns to cattle producers.

4. No-till planting of winter-annual pastures improves soil health. Winter-annual pastures are often established using traditional tillage on areas that are not suitable for row-crop production, which often leads to significant soil erosion. The objectives of this study were to determine the effects of tillage intensity on water-stable soil aggregates and their carbon and nitrogen content. The study consisted of three tillage treatments: traditional tillage, disk tillage, and no-till. After 8 years, this study showed that reducing tillage intensity from traditional tillage to disk tillage to no-till resulted in increased water-soluble aggregates, carbon, and nitrogen in the top 0- to 2-inch soil layer without increasing soil bulk density. Increased water-soluble aggregates and aggregates enriched with carbon and nitrogen are attributed primarily to tillage effects and indicate that soil quality can be maintained or enhanced through reduced tillage in a winter-annual pasture system.

5. The glucomannan from yeast helps alleviate fescue toxicosis. The chemical composition of tall fescues infected with endophytes indicates they are of high nutritive value, although average daily gain of grazing livestock is limited by toxic alkaloids produced by the endemic endophyte. A fraction of yeast added to the supplemental feed used in this study is glucomannan, which has been shown to bind naturally occurring toxins like alkaloids. To evaluate a glucomannan to mitigate fescue toxicosis, steers grazed pastures of endemic endophyte-infected tall fescue for 133 days beginning in March for two years. The three treatments were non-supplemented (control), self-fed liquid supplement, or self-fed liquid supplement containing a glucomannan. Steers consuming glucomannan gained weight more quickly than steers consuming pure supplement or control steers, and weight of glucomannan-supplemented steers was 6% greater than that of steers consuming the pure supplement. Overall, the inclusion of glucomannan in the supplement enhanced body weight gain, indicating that the effects of the toxicosis had been partially overcome.

6. New cultivars of tall fescue may make cattle producers millions of dollars. New cultivars of non-toxic endophyte containing tall fescues may provide cattle with additional annual weight gain because the new non-toxic endophytes do not produce toxic alkaloids that deters weight gain. This research was conducted by an ARS scientist at Woodward, Oklahoma, to compare two non-toxic endophyte-infected tall fescue cultivars with the toxic endophyte-infected Kentucky-31 and an endophyte-free tall fescue in southwest Arkansas. Eleven pastures were planted to one of four different tall fescue types: one contained toxic endophyte, one was endophyte free, and two contained non-toxic endophytes. Pastures were grazed by beef calves for 2 years. After 2 grazing seasons, pastures that contained the three endophyte-infected tall fescues had greater stand counts than the endophyte-free tall fescue. Ending body weight and total weight gain per acre were greater for calves grazing the two non-toxic endophyte-infected tall fescues compared with the tall fescue containing toxic endophyte. The persistence of non-toxic endophyte-infected tall fescues was greater than the endophyte-free variety, and they produced the most weight gain per acre. These findings demonstrate the value of developing new non-toxic endophyte-infected tall fescue for the cattle industry.


Review Publications
Gregorini, P., Gunter, S.A., Bowman, M.T., Caldwell, J.D., Masino, C.A., Coblentz, W.K., Beck, P.A. 2011. Effect of herbage depletion on short-term foraging dynamics and diet quality of steers grazing wheat pastures. Journal of Animal Science. 89:3824-3830.

Wine, M., Zou, C., Bradford, J.A., Gunter, S.A. 2012. Runoff and sediment responses to grazing native and introduced species on highly erodible Southern Great Plains soil. Journal of Hydrology. 450-451:336-341.

Gunter, S.A. 2012. Ruminant Nutrition Symposium: Modulation of metabolism through nutrition and management. Journal of Animal Science. 90:1833-1834.

Thacker, E.T., Gardner, D.R., Messmer, T.A., Guttery, M., Dahlgren, D.K. 2011. Using gas chromatography to determine winter diets of sage-grouse in Utah. Journal of Wildlife Management. 76(3):588-592.

Gunter, S.A., Thacker, E.T., Gillen, R.L., Springer, T.L., Jones, R. 2012. Effects of sand sagebrush control in southern mixed-grass prairie rangeland on cattle performance and economic return. Professional Animal Scientist. 28:204-212.

Last Modified: 10/25/2014
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