• Yield and quality of RS-2, a quackgrass X bluebunch wheatgrass hybrid

      Haferkamp, M. R.; Adams, D. C.; Borman, M. M.; Grings, E. E.; Currie, P. O. (Society for Range Management, 1995-07-01)
      Understanding the effect of defoliation frequency and N fertilization on plant growth, forage yield, and quality of RS-2, a quackgrass [Elytrigia repens (L.) Nevski.] x bluebunch wheat grass [Pseudoroegneria spicata (Pursh.) Love] hybrid, will help promote efficient use of this hybrid in livestock production systems. Plants were fertilized with 0, 112, or 224 kg N ha-1 in spring 1988 and 1989, or with a 112 + 112 kg N ha-1 split in spring and summer. One set of plants was unmowed or mowed to a 5cm stubble height once in July or August in 1988 and another set was mowed initially in May, June, July, August, September, or October 1989 and monthly thereafter through October. Peak standing crop of unmowed plants was 3,470 kg ha-1 in 1988 and 5,850 kg ha-1 in 1989. In 1989 yields of fertilized plants exceeded those of unfertilized plants by 1,000 kg ha-1. In 1988, crude protein exceeded 12% in unmowed forage and in 1989 varied from 20% in May to 8% in August. After fertilization, crude protein was increased by 2 to 4 percentage units in 1988 and by 2 percentage units in 1989, but fertilization had no effect on in vitro digestible organic matter. Regrowth contained more crude protein (15-22%) and digestible organic matter (29-40%) than unmowed forage. Sequential harvesting enhanced quality of regrowth, but standing crops did not exceed 350 kg ha-1; except in June 1989. Sixty percent of the accumulated yield was harvested with the first mowing during May through August. Plots harvested initially in September and October were only harvested once. Our findings indicate an increase in forage yield potential and forage quality of RS-2 after harvesting and fertilizing the RS-2 hybrid.
    • Weed suppression with grazing or atrazine during big bluestem establishment

      Lawrence, B. K.; Waller, S. S.; Moser, L. E.; Anderson, B. E.; Larson, L. L. (Society for Range Management, 1995-07-01)
      Weed competition is a major factor causing warm-season grass seeding failures in rangeland and cropland. With a limited number of herbicides available for weed control, grazing may reduce competing vegetation in seedings and serve as an alternative to herbicides. Many immature weedy forbs and grasses are palatable to cattle and contain high nutrient levels. Research was conducted (RCBD, 4 reps) comparing grazing by yearling cattle with chemical suppression [atrazine (6-chloro-N-ethyl-N-(methylethyl)-1, 3, 5-triazine-2, 4-diamine)] for weed control in big bluestem (Andropogon gerardii var. gerardii Vitman) seedlings at Mead, Nebr. on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll) soil. Big bluestem was seeded at 220 PLS m-2 on 8 May 1987 and 25 April 1988. Weed control practices were mob grazing, continuous stocking, early-season mob and continuous stocking, chemical suppression with atrazine (2.2 kg a.iha-1), and a control. Paddocks were mob grazed 4 times in 1987 and 2 times in 1988. Paddocks were continuously stocked from 10 June to 22 July 1987. Continuous stocking was not attempted in 1988 because nitrate (NO3-) levels in redroot pigweed (Amaranthus retroflexus L.) exceeded toxic levels (23,400 to 55,600 mg kg-1 NO3-) throughout the season. Acceptable big bluestem stands developed in 1987 and 1988, 14 and 6 plants m-2 respectively, on areas treated with atrazine. Density and frequency of big bluestem seedlings were lower on the atrazine-treated plots in 1988 due to higher levels of weed competition and reduced precipitation. Grazing treatments resulted in inadequate stands (< 1.0 plant m-2) of big bluestem in both years. Grazing is not a suitable alternative to chemical suppression for weed control for big bluestem establishment in sub-humid and humid environments where high weed populations are common.
    • Viewpoint: Grazing management and research now and in the next millennium

      Walker, J. W. (Society for Range Management, 1995-07-01)
      Livestock have been a key factor in the development of civilization, but what will their role be in the future and how should the science of rangeland management change to meet the challenges of the future? In this paper I look at current grazing management in the context of paradigm shifts and scientific revolution. The impact of livestock on rangelands occurs primarily because livestock selectively defoliate the available herbage rather than indiscriminately consuming herbage according to its availability. Grazing management via the use of traditional grazing systems does not appreciably affect selective foraging behavior. Trends of the future that will affect societal demands and available technologies include: 1) no lack of resources or food; 2) increased concern for environmental quality; 3) greater demand for open space values of rangelands; and 4) geometric increase in the availability of technologies from molecular biology to solve management problems. The 4 principles of grazing management i.e., 1) timing, 2) distribution, 3) kind/class of livestock, and 4) stocking rate, will not change. Stocking rate is the most important variable in grazing management. If stocking rate is not near the proper level then regardless of other grazing management practices employed objectives will not be met. The ability to determine the proper stocking rate will be hindered by the inability to determine carrying capacity as it varies over time. To change the grazing habits of the animals we must work directly on the genetics of the animal. However, the way we manipulate and manage grazing animals will improve, and our ability to monitor the impact of grazing must also improve. In addition to commodity production, livestock grazed on natural plant communities will also have to simultaneously impact these communities to provide the types of habitat demanded by society. The most important emerging technology for the management of grazing livestock will be genetic manipulation using both classical selection procedures and genetic engineering. New technologies for monitoring impact of livestock on the rangeland resource and for setting and adjusting stocking rates will also be critical. Interdisciplinary research must be encouraged to meet the future demands.
    • Technical Note: Fecal NIRS equation field validation

      Lyons, R. K.; Stuth, J. W.; Angerer, J. P. (Society for Range Management, 1995-07-01)
      Seven trials, independent of data used to develop fecal near infrared reflectance spectroscopy (NIRS) equations, were conducted to validate previously developed fecal NIRS equations for prediction of forage diet crude protein (CP) and in vivo-corrected digestible organic matter (DOM) under field conditions. For both crude protein and digestible organic matter, strong relationships existed between conventional chemistry values of diet samples collected with esophageal-fistulated steers and NIRS predictions from fecal samples collected from intact, mature, Brahman x Hereford cows at 72 hour after grazing was initiated in trial pastures.
    • Succession and livestock grazing in a northeastern Oregon riparian ecosystem

      Green, D. M.; Kauffman, J. B. (Society for Range Management, 1995-07-01)
      Comparisons of vegetation dynamics of riparian plant communities under livestock use and exclusions over a 10 year period were quantified in a Northeastern Oregon riparian zone. We measured species frequency, richness, diversity, evenness, and livestock utilization in 8 plant communities. Livestock grazed the study area from late August until mid September at a rate of 1.3 to 1.8 ha/AUM. Utilization varied from > 70% in dry meadows to < 3% in cheatgrass dominated stands. Ungrazed dry and moist meadow communities had significantly lower (P lesser than or equal to 0.1) species richness and diversity when compared to grazed counterparts. In the most heavily grazed communities, ruderal and competitive ruderal species were favored by grazing disturbance. In exclosures of the same communities, competitive or competitive stress tolerant species were favored. Both height and density of woody riparian species were significantly greater in ungrazed gravel bar communities. Our results indicate that influences of herbivory on species diversity and eveness varies from 1 community to another and basing management recommendation on 1 component ignores the inherent complexity of riparian ecosystems.
    • Sequence of species selection by cattle and sheep on South African sourveld

      O'Reagain, P. J.; Grau, E. A. (Society for Range Management, 1995-07-01)
      The sequence of species selection over the grazing period directly determines the effectiveness of different grazing systems. Knowledge of this sequence is also important in understanding the plant-animal interface. The sequence of tiller defoliation by cattle and sheep was compared for 7 range grasses at 4 different sites in South African sourveld. Defoliation frequency and height was monitored daily over a 6-day grazing period at each site. The sequence of species selection was the same for cattle and sheep although the acceptability of some grasses varied between animal species. Preferred species were always grazed first along with some (<20%) utilization of species of intermediate acceptability. When about 60% of the tillers of the preferred species had been defoliated, regrazing of these tillers commenced and the rate of utilization of intermediate species increased. Only after 80 to 100% of the tillers of preferred and intermediate species had been defoliated were tillers of the least-preferred species grazed. Sheep were more selective and tended to graze the least-preferred species later in the grazing period than did cattle. There was no difference between cattle and sheep in the frequency of tiller defoliation over the grazing period but tillers were defoliat- ed to a lower height (P < 0.01) and more tissue removed (P<0.01) under sheep grazing. Cattle and sheep are therefore likely to differ in their potential impact upon rangeland.
    • Responses of downy brome to nitrogen and water

      Link, S. O.; Bolton, H.; Thiede, M. E.; Rickard, W. H. (Society for Range Management, 1995-07-01)
      Downy brome (Bromus tectorum L.) is an alien grass that dominates disturbed ground in shrub-steppe ecosystems of the western United States. Responses of downy brome to added nitrogen and water were evaluated using intact soil cores obtained from an old field. Gas exchange data were gathered at the leaf and canopy scales. Stomatal conductance and net photosynthesis rates were greater at the leaf scale than at the canopy scale, decreased with time from germination, and were weakly affected by treatments. Water-use efficiency was weakly related to time from germination and treatments. Biomass was greater in the nitrogen-plus-water (7.4 g) treatment, compared with water (3.6 g), nitrogen (4.5 g), and control (3.3 g) treatments. The leaf-area index varied like biomass at the end of the experiment. Shoot nitrogen was the same in the nitrogen (2.5%) and nitrogen-plus-water (2.5%) treatments, nearly twice the level in the control (1.5%) and water (1.3%) treatments. Nitrogen-use efficiency was highest in the control (67) and water (80) treatments and lowest in the nitrogen (41) and nitrogen-plus-water (43) treatments. The most significant conclusion of this work is that gas exchange was strongly related to the time from germination and little affected by water and nitrogen while growth characters were strongly affected only when water and nitrogen were added together.
    • Predicting biomass of beaver food from willow stem diameters

      Baker, B. W.; Cade, B. S. (Society for Range Management, 1995-07-01)
      Beaver (Castor canadensis Kuhl) and willow (Salix spp.) are important components of riparian restoration on degraded western rangelands. Land managers need quantitative information to evaluate carrying capacity and potential habitat quality for beavers in riparian-willow systems. Our objectives were to determine the best model to predict biomass components of coyote willow (S. exigua Nuttall) from basal stem diameters and compare model predictions to diameter class averages. The study was conducted in a shrub-steppe ecosystem of northwestern Colorado. We estimated oven-dried weights of annual and total beaver food and total live biomass by diameter class from a sample of 160 willow stems. Several variants of a logistic function were fit with nonlinear least squares regression to select a model that best predicted mean biomass by stem diameter. A four-parameter logistic model provided the best fit for all 3 stem components. Predicted biomass estimates of beaver food and total live biomass had smaller standard errors than sample means for all 10 stem diameter class midpoints. Percentage of stem weight that was beaver food varied from 93.6% for the smallest stems to 12.2% for the largest. We concluded that the logistic model provided reliable estimates of beaver food biomass and could be used with food consumption rates and stem density data to evaluate carrying capacity for beaver or test assumptions in the beaver habitat suitability index model.
    • Grass utilization and grazing distribution within intensively managed fields in central Alberta

      Irving, B. D.; Rutledge, P. L.; Bailey, A. W.; Naeth, M. A.; Chanasyk, D. S. (Society for Range Management, 1995-07-01)
      Grazing distribution and grass utilization was evaluated in intensively managed fields in the southern Aspen Parkland near Kirriemuir, Alberta. Three fields, 130 ha in size (with dimensions .4 X 3.2 km) were grazed by 1,000 cow/calf pairs for 5 days each. Stock water was accessible only from one end of each field. Grazing distribution was evaluated by monitoring grass utilization daily during grazing and after grazing at 0.1, 0.8, 1.6, 2.4, and 3.1 km from water. Final utilization did not differ within fields, except for a decline at the maximum distance from water (3.1 km). Temporal utilization patterns existed and could best be described as a wave, with defoliation beginning near the water source on day 1 of grazing and proceeding outward from water until the ends of the fields were grazed on day 5. Final utilization was uniform; selective grazing of areas close to water was not removed by intensive management, but was masked by a rapid rate of defoliation.
    • Estimating forage intake and quality in grazing cattle: A reconsideration of the hand-plucking method

      De Vries, M. F. W. (Society for Range Management, 1995-07-01)
      The hand-plucking method for estimation of bite size and nutritive quality was tested for steers grazing at low stocking rates on heathland and in riverine grassland. Vegetation height, standing crop, and cover of distinct plant categories were determined in 13 sampling periods over 2 years. In each period bite size was estimated with 4 esophageally fistulated steers. Bite counts on different plant categories were made during sampling. The plant categories were sampled separately by hand-plucking and weighed to determine plucking size. Extrusa and hand-plucked samples were analyzed for concentrations of nitrogen and calcium. Vegetation height was a more accurate predictor of plucking size than standing crop. A curvilinear relationship was derived between plucking size and bite size. The nutritive quality of extrusa and hand-plucked samples was not significantly different. It is concluded that the application of the hand-plucking method appears successful when a stratified sampling approach to hand-plucking is followed. Future studies should examine operator-biases and how these can be minimized.
    • Elk and deer diets in a coastal prairie-scrub Mosaic, California

      Gogan, P. J. P.; Barrett, R. H. (Society for Range Management, 1995-07-01)
      We examined the diets of reintroduced tule elk (Cervus elaphus nannodes Merriam) and resident Columbian black-tailed deer (Odocoileus hemionus columbianus Richardson) inhabiting the coastal prairie-scrub mosaic of Tomales Point, the northernmost portion of the Point Reyes Peninsula, Calif., during 1979-81. The elk diet differed between years whereas the deer diet did not. The pattern of seasonal quality of elk and deer diets, as measured by fecal nitrogen (FN) was similar between species and years. This was achieved although botanical composition differed between herbivores in some seasons. Dietary overlap was lowest in the wet winter months when fecal nitrogen was highest and vegetative standing crop was lowest. Conversely, dietary overlap was highest in the dry summer months when fecal nitrogen was lowest and vegetative standing crop highest. Both herbivore species showed selection and avoidance of certain plant species in June of both years. These findings are compared to other cervid-habitat systems.
    • Effects of grasshopper control programs on rangeland breeding bird populations

      George, T. L.; McEwen, L. C.; Petersen, B. E. (Society for Range Management, 1995-07-01)
      We investigated the effects of grasshopper control methods on breeding bird populations in western rangelands. We estimated bird densities on 13 treated and 11 untreated sites before and after grasshopper control operations. Four different treatments were used in these applications: malathion, sevin-4-oil, carbaryl bait and Nosema locustae bait. There were few differences among the 4 treatments in their effects on bird community parameters (total bird density, and species richness, diversity, or evenness). Bird community parameters did not differ between spray and bait applications but sample sizes were small for bait treatments. When data from all treatments were combined for analysis, there was no difference in any of the bird community parameters between pre- and post-treatment samples. Densities of western meadowlarks (Sturnella neglecta), however, were significantly lower on treated than untreated sites 10 and 21 days after treatment. We found no relationship between changes in bird numbers 21 days post-treatment and either the size of the area treated or the date of treatment (i.e., early or late in nesting season). Malathion is an acetylcholinesterase (AChE) inhibitor, but brain AChE levels in birds collected on sites treated with malathion showed no significant inhibition. These results suggest that grasshopper integrated pest management treatments generally have little effect on breeding bird communities but some insectivorous bird species may decline on rangeland treated with broad-spectrum insecticides because of reduction in food base. Pesticide applications that have adverse impacts on birds and other nontarget wildlife that prey on grasshoppers may be counterproductive to long-term integrated pest management goals.
    • Effects of carbachol administration in cattle grazing tall larkspur-infested range

      Pfister, J. A.; Manners, G. D. (Society for Range Management, 1995-07-01)
      Tall larkspur (Delphinium barbeyi L. Huth.) toxicosis of cattle is a serious problem on western USA mountain rangelands. Manipulating the ruminal environment may decrease the susceptibility of cattle to larkspur intoxication. The cholinergic drug carbachol can greatly increase salivary flow and fluid passage rate in ruminants. Our objectives were to: (1) determine if chronic administration of carbachol altered ruminal fluid passage rate, ruminal pH, or water intake in grazing cattle, and (2) evaluate mineral salt supplementation as a prophylactic procedure for cattle grazing larkspur-infested rangelands. The study was conducted during summer of 1990 and 1991 near Yampa, Colo. Twelve heifers were divided randomly into 3 treatment groups: (1) carbachol administered at 0.01 mg kg-1 day-1 via subcutaneous osmotic minipumps; (2) mineral-salt supplement dosed intraruminally at 0.25 g kg-1 day-1; and (3) controls. Administration of carbachol either had no effect or a negative effect on ruminal fluid passage rate, ruminal pH, saliva production, and water intake compared with the controls. Carbachol had few consistent effects on serum electrolyte concentrations compared to the controls. Treatments did not influence cattle diet selection; cattle ate no larkspur during 1990, but selected larkspur for 16% of their diets during August, 1991. There was no indication that supplementation with mineral salt would attenuate larkspur toxicosis through increased dilution rates, or decreased larkspur consumption. Our results indicate that neither carbachol nor mineral supplementation will reduce animal susceptibility to larkspur toxicosis.
    • Atrazine impacts on shortgrass prairie microcosms

      Miller, M. S.; Doxtader, K. G. (Society for Range Management, 1995-07-01)
      Alterations in shortgrass ecosystem structure and function following long-term use of atrazine [6-chloro-N-ethyl-N'-(1-methylethyl)-1,3, 5-triazine,2,4-diamine] for increased secondary productivity raised concerns about sustainability of the practice. A microcosm approach was designed to 1) model the direction and temporal features of blue grama [Bouteloua gracilis H.B.K.) Lag. ex Steud.] biomass accumulation and tissue N, nitrate reductase activity, chlorophyll, total nonstructural carbohydrate, and phosphorus (P) levels following atrazine applications of 0.84 and 2.24 kg ha-1 and hydroxyatrazine (6-hydroxy-N-ethyl-N'-(1-methylethyl)-1,3, 5-triazine,2,4,-diamine) at 1.12 kg ha-1, and 2) to relate plant growth and metabolism changes to possible short- and long-term modifications of soil microbial abundance and activities associated with C and N transformations. Atrazine applied to dormant plant-soil microcosms reduced below-ground (crown plus root) biomass and shoot total nonstructural carbohydrate levels during regrowth. Atrazine application increased shoot chlorophyll content, N levels, and nitrate reductase activity, but not total plant N content. Decreased below-ground biomass accumulation, and increased shoot N and nitrate reductase activity levels were linked to decreased total nonstructural carbohydrate availability. Total plant P levels were highest at the intermediate atrazine rate. Differences in soil microbial biomass and activities, and chemical properties resulted primarily from presence of blue grama and duration of plant regrowth. Soil nitrifying activity was depressed in soil previously exposed to atrazine whether or not blue grama was present. Hydroxyatrazine was not identified as an important factor in observed plant or soil changes. Atrazine may alter shortgrass system structure and function by immediate impacts on primary producers and long-term impacts on soil microbial processes.