• Factors affecting dietary preferences for genotypes of a hybrid wheatgrass

      Truscott, D. R.; Currie, P. O. (Society for Range Management, 1987-11-01)
      Interspecific hybridization of grasses represents a valuable plant breeding procedure for developing new species with superior grazing value for livestock. Evaluations were made of the hybrid cross between quackgrass (Elytrigia repens [L.] Beauv.) × bluebunch wheatgrass (Pseudoroegneria spicata [Pursh.] Scribn and Smith) to determine how animal preferences for these hybrids were influenced by grazing season and year. Significant differences in the preference shown by steers as measured by bite counts in 1981 and percent utilization (P<0.01) in 1982 existed among the 46 clonal lines for each of the 2 successive years. Preference rankings for lines selected the first year were not identical to those selected a second year although lines with high preference rankings the first year were generally preferred the second year. A clonal line, designated line 30, was most preferred in 7 of 8 subtrials in 1981 and ranked in the top 3 preferred plants in all trials in 1982. There was a 4-week period in early summer when preference differences were minimal. It was attributed to the abundant regrowth on all lines at this time and was found to have a significant (P<0.01) effect on steers' dietary choices.
    • Germination of downy brome from southern Kansas, central Oklahoma, and north Texas

      Milby, T. H.; Johnson, F. L. (Society for Range Management, 1987-11-01)
      Mature downy brome (Bromus tectorum L.) seeds collected in Texas, Oklahoma, and Kansas in mid-June did not germinate at summer temperatures even when supplied with adequate moisture. The after-ripening of seeds for 3 months produces germination of 50% or more in most populations, as does subjecting fresh seeds to November temperature regimes. These results are similar to those reported for downy brome seeds from eastern Washington, central Idaho, and central California in which fresh seeds are dormant. They differ from those reported for seeds from Montana, northern California, northern and western Nevada, southern Idaho, and northern Utah in which fresh seeds germinate at high percentages. Dormancy of fresh seeds from the Southern Great Plains delays downy brome germination until the fall season at which time rainfall and other climatic conditions are more favorable for its survival.
    • Germination rate at low temperature: rubber rabbitbrush population differences

      McArthur, E. D.; Meyer, S. E.; Weber, D. J. (Society for Range Management, 1987-11-01)
      The concept that low-temperature germination response is a population rather than a species characteristic has implications for range seeding. The success of a seeding could depend on the ability of the seed source to associate the appropriate degree of risk with germination in the cold at a particular site. Germination rate at 3 degrees C was determined for 27 seed collections of rubber rabbitbrush (Chrysothamnus nauseosus [Pall.] Britt) belonging to 9 subspecies and collected in 5 states. Marked differences in low-temperature germination rate were observed. Relative percentage of germination at 14 days varied from 0.4 to 100, while the period required to reach 50% relative germination varied from 5 to 96 days. Germination rate was negatively correlated with a climatic index of winter frost risk to seedlings at the site and seed origin. Warm desert collections germinated fastest, while montane and high latitude collections germinated slowest. Many collections from mid-elevation sites showed the bet-hedging strategy of asynchronous germination in the cold. Germination rate was not correlated with subspecific identity. Subspecies of wide ecological amplitude showed nearly the whole range of germination rate response. The possibility that other important range species might show similar patterns of variation in low-temperature germination response merits investigation.
    • Interplanting crested wheatgrass with shrubs and alfalfa: effects of competition and preferential clipping

      Pendery, B. M.; Provenza, F. D. (Society for Range Management, 1987-11-01)
      Planting palatable shrubs and legumes into an established stand of crested wheatgrass (Agropyron desertorum and A. cristatum) could increase forage yield and nutritional quality. Preferential grazing of the grass and legume in spring may enhance establishment of shrub seedlings. Seedlings of 3 species of shrubs (Artemisia tridentata ssp. vaseyana, Kochia prostrata, and Atriplex canescens) were transplanted into plots of crested wheatgrass using a replacement series design. Each species of shrub was grown with the grass, and with the grass and alfalfa (Medicago sativa cv. 'Ladak'); each of the 5 species was also grown in monoculture. Swards were either uncut or the grass and alfalfa were clipped while actively growing in late May and early June. Shrubs had greater current annual growth (CAG) (P is lesser than or equal to 0.001), higher relative yields (P is lesser than or equal to 0.05), lower mortality (P is lesser than or equal to 0.001), and more inflorescences (P≤0.001) in monoculture than in mixture. The grass had greater CAG in mixture than in monoculture (P is lesser than or equal to 0.05), and the grass and alfalfa had greater relative yield in mixture than in monoculture (P is lesser than or equal to 0.05). Clipping crested wheatgrass and alfalfa increased shrub CAG (P is lesser than or equal to 0.01), reduced mortality (P is lesser than or equal to 0.001), and increased the number of inflorescences (P is lesser than or equal to 0.01), but the increase in shrub CAG and flowering due to clipping was not as great as when shrubs were grown in monoculture. There were no interactions between competition and clipping (P>0.05). In terms of CAG, mortality, and flowering, A. tridentata grew better than K. prostrata, which grew better than A. canescens, but these relationships involved complex interactions. The contribution of shrubs to the biomass in mixture was minor; although alfalfa dominated three-way mixture yields, the grass also made a substantial contribution. Since competition was more important in determining shrub response than clipping and the 2 effects were independent, it is probably more important to reduce interspecific competition than to modify grazing practices when planting shrubs in a crested wheatgrass stand.
    • Optimal economic timing of range improvement alternatives: southern High Plains

      Ethridge, D. E.; Pettit, R. D.; Sudderth, R. G.; Stoecker, A. L. (Society for Range Management, 1987-11-01)
      Profit maximizing combinations of livestock enterprises, plant control practices, and grazing management systems for ranches in the southern High Plains were examined. A typical ranch and a multi-period linear programming model were used to determine the combinations and timing of improvement practices and enterprises to maximize discounted net income with different investement capital constraints, cattle prices, and discount rates. All solutions included chemical control of sand shinnery oak (Quercus havardii) and a rotation grazing system. Timing of improvements and net income were affected by size of investment capital constraint.
    • Potential for hydrocyanic acid poisoning of livestock by indiangrass

      Vogel, K. P.; Haskins, F. A.; Gorz, H. J. (Society for Range Management, 1987-11-01)
      Hydrocyanic acid or prussic acid poisoning of livestock by sorghums [Sorghum bicolor (L.) Moench] and sudangrasses [Sorghum sudanese (Piper) Stapf] is caused by the digestive liberation of hydrocyanic acid (HCN) from the cyanogenic compound, dhurrin [(S)-p-hydroxymandelonitrile β-D-glucopyranoside] found in tissue of these plants. Recent research documented that dhurrin is also present in indiangrass [Sorghastrum nutans (L.) Nash] seedlings. The purpose of this study was to determine the hydrocyanic acid potential (HCN-p) of forage from established stands of indiangrass. Five cultivars representative of indiangrass germplasm of the Great Plains were sampled during the growing season for 2 years from 2 sites in eastern Nebraska. The HCN-p of the indiangrass sampled in this study exceeded 750 mg-1 kg dry wt. (dangerous level) only in spring when new growth was 20 cm tall or less. Levels were less than 500 mg-1 kg (safe) when new growth was at least 40 cm tall and were very low (<200 mg-1 kg) or not detected when the forage was over 1 m tall. Pure stands of indiangrass that are grazed when the new growth is less than 20 cm tall could be lethal to livestock.
    • Seasonal diets of herded sheep grazing Douglas-fir plantations

      Leininger, W. C.; Sharrow, S. H. (Society for Range Management, 1987-11-01)
      Use of livestock for biological weed control in timber plantations is gaining popularity in the United States and elsewhere. Efficient use of livestock to control unwanted brush relies upon knowledge of livestock feeding habits. A study was conducted during 1981 and 1982 to determine seasonal diets of herded sheep grazing cutover Douglas-fir (Pseudotsuga menziesii) forests in the Coast Range of Oregon. Study sites included both 4- to 6-year-old non-grass-seeded and 2-year-old grass-seeded plantations. Sheep grazing was monitored in spring, summer, and late summer. Forage on offer ranged from 764 to 2,459 kg/ha. Vegetational composition of sheep diets varied by year, season, and plantation age class. Averaged over the 2 years of grazing, graminoids and forbs were nearly equal, at approximately 40% each, in sheep diets in older plantations. In contrast, diets of sheep in young grass-seeded plantations averaged 70% graminoids and only 16% forbs. Ferns were a minor component (<2%) of sheep diets in both plantation age classes. Browse averaged 15 and 12% of sheep diets in old and young plantations, respectively. Douglas-fir was most palatable to sheep in spring soon after bud break. It was generally avoided, however, and never comprised more than 3% of sheep diets. Our data suggest that sheep can be most effectively used for biological control of unwanted brush species during summer and late summer when differences in relative preference indices for target brush species and Douglas-fir are greatest.
    • Seasonal dynamics of minerals in forages at the Texas Experimental Ranch

      Greene, L. W.; Pinchak, W. E.; Heitschmidt, R. K. (Society for Range Management, 1987-11-01)
      Range livestock derive the bulk of their dietary mineral intake from forages that are often deficient in one or more essential minerals. The objective of this study was to quantify the seasonal dynamics of phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) concentrations in the dominant native forages at the Texas Experimental Ranch. Concentrations were estimated by class of tissue (live and dead) for 5 species/species groups: sideoats grama (Bouteloua curtipendula Michx.), Texas wintergrass (Stipa leucotricha Trin. and Rupr.), annual grasses, other warm-season grasses, and forbs. The study spanned a period of 2 years and included 16 sample dates. Although P, Mg, and K concentrations varied significantly among species and date, they varied primarily as a function of class of tissue. Averaged across dates and species, concentrations of P, Mg, and K in live tissue averaged 0.12, 0.13, and 2.02%, respectively, while concentrations in dead tissue averaged 0.04, 0.09, 0.57%, respectively. As a result, seasonal differences in whole plant concentrations of P, Mg, and K were closely linked to seasonal growth dynamics as they affect live/dead ratios. Ca concentrations were affected more by species than class of tissue. Averaged across dates, Ca concentrations in live tissue averaged 0.55, 0.40, 0.42, 0.35, and 1.80% in annual grasses, Texas wintergrass, sideoats grama, other warm-season grasses and forbs, respectively, while concentrations in dead tissue averaged 0.41, 0.40, 0.41, 0.36, and 0.96%, respectively. It is concluded that considerations must be given to the potential effect that a given treatment may have on plant growth dynamics to properly interpret its effect on whole plant concentrations of minerals.
    • Selective control of annual bromes in perennial grass stands

      Currie, P. O.; Volesky, J. D.; Hilken, T. O.; White, R. S. (Society for Range Management, 1987-11-01)
      Three soil-active herbicides: atrazine [6-chloro-N-ethyl]-N1-(1-methyethyl)-1,3,5-triazine-2,4-diamine]; propham (1-methylethyl phenyl carbamate); and pronamide [3,5-dichloro(N-1,1-dimethyl-2-propynyl)benzamide] were applied in the fall, postemergence to annual bromegrasses at 2 rates. These herbicides were evaluated for their efficacy in selective control of cheatgrass (Bromus tectorum L.) and Japanese brome (Bromus japonicus Thunb.) in perennial stands of crested wheatgrass (Agropyron cristatum [L.] Gaertn.), pubescent wheatgrass (Thinopyrum intermedium Host), Russian wildrye (Psathrostachys juncea [Fisch.] Nevski), and western wheatgrass (Pascopyrum smithii (Rydb.) Löve) and blue grama (Bouteloua gracilis) [H.B.K.] Lag. Ex Griffiths. Yields of annual bromegrasses and perennial grasses and crude protein (CP), phosphorus and total nonstructural carbohydrate (TNC) content of perennial grasses were measured 2 consecutive years after the single herbicide application. Yields of annual bromegrasses from the 3 herbicide treatments averaged 91 and 47% less than those of the control the first and second year posttreatment, respectively. Pronamide provided substantially better control the second year posttreatment than the other 2 herbicides. Yields of perennial grasses in the majority of the herbicide treatment-study site combinations were significantly increased the first year posttreatment (P<0.10). Crude protein of perennial grasses was increased in the atrazine treatment. Atrazine at 0.6 kg/ha was the most cost-effective herbicide for decreasing competition of annual bromegrasses and increasing yield of perennial grasses.
    • Use of new rangeland seedings by black-tailed jackrabbits

      McAdoo, J. K.; Longland, W. S.; Cluff, G. J.; Klebenow, D. A. (Society for Range Management, 1987-11-01)
      Black-tailed jackrabbit (Lepus californicus) use of 2 new rangeland seedings in northern and central Nevada was determined by fecal pellet counts for the first growing seasons following seeding establishment. Jackrabbit use was an inverse function of seeding size (as indicated by distance from seeding edges to midpoints). Use was uniformly high for a small (50-ha) seeding from its edge to its midpoint. A larger (400-ha) seeding received significantly higher use at the edge than at 100-m intervals extending to the 400-m midpoint. Jackrabbit use of seedings was higher during late summer than during early summer. Jackrabbit abundance was significantly higher in sagebrush habitat adjacent to a new seeding than in similar habitat away from the seeding. Our results suggest that forage availability is a factor influencing use of seedings, and predation risk may also be involved.