• Review of toxic glycosides in rangeland and pasture forages

      Majak, W. (Society for Range Management, 2001-07-01)
      Ruminants are a diverse group of mammals, both domestic and wild species, that exhibit microbial fermentation prior to gastrointestinal activity. During the digestive process, glycosides and other natural products are exposed to ruminal microorganisms and metabolised as substrates. Most compounds are converted into nutrients but some become toxic metabolites. At least 10 types of toxic glycosides occur in forage species. Glycosides are characterized by the presence of one or more sugars linked to the alcohol or thiol functions of the non-sugar portion of the molecule, which is called the aglycone. The biological activity of the glycoside is usually determined by the chemical nature of the aglycone. The aglycones are released by microbial enzymes and may undergo further enzymatic or non-enzymatic transformations to yield toxic metabolites that can be absorbed from the gastrointestinal tract. Microbial detoxification of the aglycone is also possible. Further biotransformation of the aglycone can occur in the liver. A review is presented on glycosides that are toxic to ruminants. The discussion covers aliphatic nitrocompounds, cyanogenic glycosides, cardiac glycosides, saponins, glucosinolates, diterpenoid glycosides, bracken glycosides, calcinogens, phenolic glycosides and ranunculin. Clinical signs of poisoning and treatment of livestock as well as management strategies for the prevention of poisoning are considered.
    • Practical measures for reducing risk of alfalfa bloat in cattle

      Majak, W.; Hall, J. W.; McAllister, T. A. (Society for Range Management, 2001-07-01)
      Frothy bloat in cattle is a serious problem and is difficult to manage under field conditions as it progresses rapidly from early signs of distension to acute distress. Scientists at Agriculture and Agri-Food Canada centres in Western Canada are committed to the development of bloat-free alfalfa grazing systems, which may require feed additives or supplements. As well, a new cultivar of alfalfa (AC Grazeland), selected for a low initial rate of digestion, will soon be available. In grazing trials the cultivar reduced the incidence of bloat by an average of 56% compared with the control cultivar (Beaver). Commonly accepted mineral mixes for the prevention of bloat were tested and found ineffective but we have confirmed that poloxalene (Bloatguard®) is 100% effective if it is given intraruminally at the prescribed dose. However, under practical conditions, poloxalene can only be offered free choice and protection from bloat cannot be guaranteed. We have also shown that the water soluble polymer, Blocare® 4511, when used in the water supply is 100% effective in bloat prevention. This product is not yet registered in North America. Other strategies for bloat prevention will be discussed, including the selection of growth stages and grazing schedules, and the reduction of risk by wilting alfalfa or combining it with tannin-containing forages.
    • Anti-quality factors associated with alkaloids in eastern temperate pasture

      Thompson, F. N.; Stuedemann, J. A.; Hill, N. S. (Society for Range Management, 2001-07-01)
      The greatest anti-quality associated with eastern temperature pasture grasses is the result of ergot alkaloids found in endophyte-infected (Neotyphodium ceonophialum) tall fescue (Festuca arundinacea Schreb.) The relationship between the grass and the endophyte is mutualistic with greater persistence and herbage mass as a result of the endophyte. Ergot alkaloids reduce growth rate, lactation, and reproduction in livestock. Significant effects are the result of elevated body temperature and reduced peripheral blood flow such that necrosis may result. Perturbations also occur in a variety of body systems. Planting new pastures with seed containing a "non-toxic" endophyte appears to be a potential solution. Ergotism results from the ingestion of the scelerotia of Claviceps purpurea containing ergot alkaloids found on seed heads. Ergotism resembles the effects of endophyte-infected tall fescue. Endophyte-infected perennial ryegrass (Lolium perenne L.) contains ergot and lotirem alkaloids that result in reduced growth and tremors. Reed canarygrass (Phalaris Anundinacba L.) contains tryptamine, hordenine and gramine alkaloids that reduce growth. Annual ryegrass (Lolium multiplorum L. may contain galls with cornetoxins which result in neurological signs.
    • Effects of proanthocyanidins on digestion of fiber in forages

      Reed, J. D. (Society for Range Management, 2001-07-01)
      The ability of proanthocyanidins (PA) to form insoluble complexes with proteins and polysaccharides affects fiber digestion and analysis. This review discusses these effects in relationship to the application of the detergent system of forage analysis. A fraction of the PA in plants remains after extraction for analysis. Insoluble PA may be a natural part of the plant cell wall or may be insoluble because of high molecular weight and post harvest reactions. These reactions increase the amount of insoluble PA and decrease the amount of soluble PA. The butanol-HCl assay is the most suitable method for analysis of insoluble PA. Insoluble PA are associated with negative apparent digestion coefficients for acid-detergent lignin (ADL), neutral-detergent insoluble N and acid-detergent insoluble N. The addition of sodium sulfite to neutral detergent eliminates insoluble PA from NDF. However, the addition of sodium sulfite to neutral detergent will give misleading results in relationship to true digestibility of protein. The difference between fiber fractions that are prepared with and without the addition of sodium sulfite to neutral-detergent may estimate the amount of PA/protein complex associated with NDF. A better understanding of the relationship between PA structure and function is necessary to manipulate PA in forages through breeding or genetic engineering. The interaction between PA and fiber analysis and digestion is an important component of this research.
    • Anti-quality effects of insects feeding on rangeland plants: A review

      Campbell, J. B. (Society for Range Management, 2001-07-01)
      The anti-quality effects of the major groups of insects that utilize rangeland plants for food is discussed. The biology, ecology, geographical distribution and economic thresholds of grasshoppers, crickets, Western harvester ants, ranch caterpillars, big-eyed or black grass bugs, and white grubs are reviewed. Also discussed are practical pest management strategies if they exist. Most of these rely on the integration of good range management practices and the control strategy.
    • Alkaloids as anti-quality factors in plants on western U.S. rangelands

      Pfister, J. A.; Panter, K. E.; Gardner, D. R.; Stegelmeier, B. L.; Ralphs, M. H.; Molyneux, R. J.; Lee, S. T. (Society for Range Management, 2001-07-01)
      Alkaloids constitute the largest class of plant secondary compounds, occurring in 20 to 30% of perennial herbaceous species in North America. Alkaloid-containing plants are of interest, first because alkaloids often have pronounced physiological reactions when ingested by livestock, and second because alkaloids have distinctive taste characteristics. Thus, alkaloids may kill, injure, or reduce productivity of livestock, and have the potential to directly or indirectly alter diet selection. We review 7 major categories of toxic alkaloids, including pyrrolizidine (e.g., Senecio), quinolizidine (e.g., Lupinus), indolizidine (e.g., Astragalus), diterpenoid (e.g., Delphinium), piperidine (e.g., Conium), pyridine (e.g., Nicotiana), and steroidal (Veratrum-type) alkaloids. Clinically, effects on animal production vary from minimal feed refusal to abortion, birth defects, wasting diseases, agalactia, and death. There are marked species differences in reactions to alkaloids. This has been attributed to rumen metabolism, alkaloid absorption, metabolism, excretion or directly related to their affinity to target tissues such as binding at receptor sites. In spite of alkaloids reputed bitter taste to livestock, some alkaloid-containing plant genera (e.g., Delphinium, Veratrum, Astragalus, Oxytropis, and Lupinus) are often readily ingested by livestock. Management schemes to prevent losses are usually based on recognizing the particular toxic plant, knowing the mechanism of toxicity, and understanding the temporal dynamics of plant alkaloid concentration and consumption by livestock. Once these aforementioned aspects are understood, losses may be reduced by maintaining optimal forage conditions, adjusting grazing pressure and timing of grazing, aversive conditioning, strategic supplementation, changing livestock species, and herbicidal control.
    • Animal health problems caused by silicon and other mineral imbalances

      Mayland, H. F.; Shewmaker, G. E. (Society for Range Management, 2001-07-01)
      Plant growth depends upon C, H, O, and at least 13 mineral elements. Six of these (N, K, Ca, Mg, P, and S) macro-elements normally occur in plants at concentrations greater than 1,000 mg kg(-1) level. The remaining micro-elements (B, Cl, Cu, Fe, Mn, Mo, and Zn) normally occur in plants at concentrations less than 50 mg kg(-1). Trace amounts of other elements (e.g., Co, Na, Ni, and Si) may be beneficial for plants. Silicon concentrations may range upwards to 50,000 mg kg(-1) in some forage grasses. Mineral elements required by animals include the macro-elements Ca, Cl, K, Mg, N, Na, P, and S; the trace or micro-elements Co, Cu, Fe, I, Mn, Mo, Se, and Zn; and the ultra-trace elements Cr, Li, and Ni. When concentrations of these elements in forages get 'out of whack' their bioavailability to animals may be jeopardized. Interactions of K x Mg x Ca, Ca x P, Se x S, and Cu x Mo x S are briefly mentioned here because more detail will be found in the literature. Limited published information is available on Si, so we have provided more detail. Silicon provides physical support to plants and may reduce susceptibility to pests. However, Si may have negative effects on digestibility and contribute to urinary calculi in animals.
    • Herbivore response to anti-quality factors in forages

      Launchbaugh, K. L.; Provenza, F. D.; Pfister, J. A. (Society for Range Management, 2001-07-01)
      Plants possess a wide variety of compounds and growth forms that are termed "anti-quality" factors because they reduce forage value and deter grazing. Anti-quality attributes can reduce a plant's digestible nutrients and energy or yield toxic effects. Herbivores possess several adaptive mechanisms to lessen the impacts of anti-quality factors. First, herbivores graze selectively to limit consumption of potentially harmful plant compounds. Grazing animals rely on a sophisticated system to detect plant nutritional value or toxicity by relating the flavor of a plant to its positive or negative digestive consequences. Diet selection skills are enhanced by adaptive intake patterns that limit the deleterious effects of plant allelochemicals; these include cautious sampling of sample new foods, consuming a varied diet, and eating plants in a cyclic, intermittent, or carefully regulated fashion. Second, grazing animals possess internal systems that detoxify or tolerate ingested phytotoxins. Animals may eject toxic plant material quickly after ingestion, secrete substances in the mouth or gut to render allelochemicals inert, rely on rumen microbes to detoxify allelochemicals, absorb phytochemicals from the gut and detoxified them in body tissues, or develop a tolerance to the toxic effects of plant allelochemicals. Understanding the behavioral and metabolic abilities of herbivores suggests several livestock management practices to help animals contend with plant anti-quality characteristics. These practices include offering animals proper early life experiences, selecting the appropriate livestock species and individuals, breeding animals with desired attributes, and offering nutritional or pharmaceutical products to aid in digestion and detoxification.
    • Lignin and fiber digestion

      Moore, K. J.; Jung, H. J. G. (Society for Range Management, 2001-07-01)
      Lignin is a polymer formed from monolignols derived from the phenylpropanoid pathway in vascular plants. It is deposited in the cell walls of plants as part of the process of cell maturation. Lignin is considered an anti-quality component in forages because of its negative impact on the nutritional availability of plant fiber. Lignin interferes with the digestion of cell-wall polysaccharides by acting as a physical barrier to microbial enzymes. Lignification therefore has a direct and often important impact on the digestible energy (DE) value of the forage. There are a number of plant-related factors that affect lignification in individual plants and plant communities. Lignification is under genetic control and there are considerable differences in lignin concentration and composition among species and even genotypes within species. Genetic differences in lignification are first expressed at the cellular level and are affected by biochemical and physiological activities of the cell. As cells differentiate, differences in lignification occur depending on the tissues and organs being developed. Lignification tends to be most intense in structural tissues such as xylem and sclerenchyma. Plant organs containing high concentrations of these tissues, such as stems, are less digestible than those containing lower concentrations. The relative proportion of lignified tissues and organs typically increases as plants mature so there is often a negative relationship between digestibility and maturity. All of these plant processes respond to environmental factors that can affect the extent and impact of lignification. Temperature, soil moisture, light, and soil fertility can have either direct or indirect effects on lignification. The most useful management practices for minimizing the negative effects of lignification are manipulation of the plant community such that it contains more desirable species and harvest management to maintain plants in a vegetative stage of development.
    • Structural anti-quality characteristics of range and pasture plants

      Laca, E. A.; Shipley, L. A.; Reid, E. D. (Society for Range Management, 2001-07-01)
      Structural anti-quality characteristics are physical plant traits that reduce the performance and productivity of herbivores and quality of their agricultural products. Most structural anti-quality characteristics of plants affect the rate at which herbivores gather and ingest forages, reducing the total amount of food obtained or increasing the time necessary to obtain food. Structural anti-quality can substantially influence searching time (e.g., plant crypticity, distribution), cropping time (e.g., plant fibrousness, tensile and shear strength), and bite size (e.g., plant canopy structure, spinescence). Plant structural characteristics can also reduce digestion (e.g., silica), cause injury (e.g., spines, awns, burrs, calluses), or reduce the quality of animal products, such as wool (e.g., propagules). The effects of structural antiquality characteristics depend on the morphology of the herbivore, especially its size, the morphology of the focal plant, and their context within the habitat. Integrated grazing management plans should consider options to reduce the negative effects of structural anti-quality. Carefully selecting appropriate livestock species with previous experience, and the appropriate season of grazing can minimize anti-quality on rangelands. Because structural anti-quality may actually promote sustainability of grazing systems by preventing severe defoliation, or by providing refuges for highly desirable forages, it may not be desirable to completely counteract their effects.
    • Anti-quality components in forage: Overview, significance, and economic impact

      Allen, V. G.; Segarra, E. (Society for Range Management, 2001-07-01)
      Although recognized in importance from the dawn of history, forages have too often been underestimated and undervalued perhaps in part because animal performance has frequently failed to reflect apparent forage quality. Anti-quality components, diverse impediments to quality, have evolved as structural components and as secondary metabolites. They include mineral imbalances or can be related to the presence of insects and diseases. Animal behavior and adaptation are increasingly recognized as important aspects of anti-quality factors. An anti-quality component may reduce dry matter intake, dry matter digestibility, or result in nutritional imbalances in animals. They can act as a direct poison compromising vital systems, result in abnormal reproduction, endocrine function, and genetic aberrations, trigger undesirable behavior responses, or suppress immune function leading to increased morbidity and mortality. The economic impact of anti-quality factors on individual herds can be devastating but definable. Broadscale economic impacts of anti-quality factors are far more difficult to estimate. A loss of 0.22 kg/day in potential gain of stocker cattle due to anti-quality factors during a 166-day grazing season translates into a loss of about 55/steer at 1.45/kg or over 2 billion annually when applied to the U.S stocker cattle. Economic losses to tall fescue (Festuca arundinacea Schreb.) toxicosis in the U.S. beef industry are probably underestimated at 600 million annually. Reproductive and death losses of livestock due to poisonous plants have been estimated at 340 million in the 17 western states alone. These examples of economic losses due to anti-quality factors may be upper bounds of actual losses but even if a small proportion of the expected losses were eliminated through research, the potential payoff would be extremely high.
    • Carbon and nitrogen dynamics in elk winter ranges

      Menezes, R. S. C.; Elliott, E. T.; Valentine, D. W.; Williams, S. A. (Society for Range Management, 2001-07-01)
      Recent increases in elk (Cervus elaphus L.) herbivory and changes in hydrology towards drier conditions have contributed to declines in willow (Salix spp. L.) communities in the winter ranges for elk in Rocky Mountain National Park. In 1994, we constructed 12 large elk exclosures in 2 watersheds of the winter range for elk in the park, and conducted field experiments from 1995 to 1999 to investigate the effects of herbivory and proximity to surface water on the dynamics of C and N. Litterfall biomass averaged 65.6 and 33.0 g m(-2) inside and outside the exclosures, respectively. Elk herbivory increased (P < 0.05) N concentration of willow litter from 1.25 to 1.49%, but there were no differences in losses of C and N from litterbags placed in grazed and ungrazed plots in any of the growing seasons. Carbon losses from litterbags were higher in lower landscape positions (P = 0.001), in comparison to upper landscape positions. Shoot biomass of willow plants fertilized with N averaged 27.3 g and was higher (P < 0.05) than that of unfertilized plants, which averaged 20.2 g, indicating that N availability limits plant growth in our study sites. Elk herbivory had no effect on soil inorganic N availability, even though we estimated that the return of N to the soil in grazed plots could be as much as 265% of the N return in exclosed plots. In the long-term, greater return of N to the soil combined with increased litter quality in the grazed plots could contribute to increases in N cycling rates and availability, and these changes could affect ecosystem structure and function in the winter range for elk in Rocky Mountain National Park.
    • 'Immigrant' forage kochia seed viability as impacted by storage methods

      Stewart, A.; Anderson, V. J.; Kitchen, S. G. (Society for Range Management, 2001-07-01)
      'Immigrant' forage kochia (Kochia prostrata (L.) Schrad.) is a valuable introduced subshrub, often used in reclamation plantings and seedings on western rangelands. Seedling establishment is best from fresh seed; however, many users plant stored seed and experience poor seeding success. One cause for failure is loss of seed viability in storage. Forage kochia seed was harvested on 4 dates in fall 1996 from 2 sites (wildland and irrigated) and tested for viability when fresh and after storage treatments. Storage treatments included low and high seed water contents (2-6% and 12-16%), cold and warm storage temperatures (2 degrees and 25 degrees C), and duration of storage (4, 8, and 12 months). Mature, highly viable forage kochia seed remains viable in storage longer than seed harvested prematurely. Low seed water content (2-6%) is essential to preserving maximum seed viability. Storing seed at a cold temperature (2 degrees C) is also helpful in maintaining viability.
    • Endophytic fungi in Canada wild rye in natural grasslands

      Vinton, M. A.; Kathol, E. S.; Vogel, K. P.; Hopkins, A. A. (Society for Range Management, 2001-07-01)
      Some grasses harbor endophytic fungi living in intercellular spaces in the leaves, stems and reproductive organs. The fungi can dramatically affect the physiology and ecology of plants. For example, fungi may produce toxins that deter herbivores and they may alter the water status of the plant to increase drought tolerance. The distribution of fungal infection in natural plant populations is unknown for many host species. We investigated the occurrence of endophytic fungi in Elymus canadensis L. (Canada wild rye) from 13 remnant prairie sites in the midwest and 23 sites in the southern Great Plains. Collections of plant tissue came from Nebraska, Kansas, Minnesota, Iowa, Missouri, Illinois, Oklahoma, and Texas. All midwest plants were grown in a common garden site in eastern Nebraska. Seeds collected from Oklahoma and Texas accessions were planted in the greenhouse. At least 3 tillers from 2 plants of each accession were screened for endophytes, using light microscopy. The endophytic fungus was found in seed of all accessions and in plants from all but 4 accessions. The functional significance of the fungus is unclear, but it may affect plants by enhancing productivity or deterring herbivores. The widespread occurrence of endophytic fungi in natural populations of E. canadensis suggests that the plant-fungal association may be long-standing and important in the evolution and success of this native prairie species.
    • Low density of prickly acacia under sheep grazing in Queensland

      Tiver, F.; Nicholas, M.; Kriticos, D.; Brown, J. R. (Society for Range Management, 2001-07-01)
      Populations of an introduced woody weed, prickly acacia (Acacia nilotica (L.) Delile ssp. indica (Benth.) Brenan syn. Acacia arabica (Lam.) Willd. ssp. indica Benth.), were surveyed at 4 sites in central Queensland. There is a significantly lower frequency of plants of 3 m in height within populations which have been grazed by sheep, indicating that browsing by sheep reduces regeneration. There were higher losses of seedlings at a sheep-grazed site than at cattle-grazed sites. These results support previous assertions that prickly acacia is regenerating more successfully on cattle properties, because cattle both disperse seeds and are less effective herbivores. In regions of low annual rainfall, prickly acacia is capable of forming dense stands (up to 2,700 shrubs ha(-1)) in lowland landscape types. Stands are less dense in upland landscapes (maximum of 718 shrubs ha(-1)). Of most concern is that in regions of high annual rainfall prickly acacia can form extremely dense thickets across most landscape types (up to 3,400 shrubs ha(-1)). We suggest that prickly acacia is most likely to become a management problem on cattle properties, and an extreme problem in high annual rainfall areas. The inclusion of sheep in livestock rotations may be an effective control measure in the Mitchell Grasslands, but this may not always be possible. A high priority is to prevent prickly acacia from expanding its range into equivalent high rainfall areas within Queensland, and also in the Northern Territory, northern New South Wales, and Western Australia. This could be achieved by quarantining livestock which have come from infested properties until seeds have passed through the digestive tract, after about 6 days. Management strategies at the property level should aim to prevent further spread of prickly acacia by controlling cattle movements between paddocks during periods when cattle are ingesting pods and seeds.
    • A proposed method for determining shrub utilization using (LA/LS) imagery

      Quilter, M. C.; Anderson, V. J. (Society for Range Management, 2001-07-01)
      Utilization of plant above ground biomass has continued to be a critical yet difficult assessment in rangeland monitoring. Shrub size and woody structure further compound the measurement of shrub biomass utilization. This study was designed to determine the potential utility of low altitude/large scale (LA/LS) imagery in assessing shrub utilization. A near monoculture of Ceriotoides lanata (Pursh) J.T. Howell (winterfat) located in the western desert shrubland of Utah was used to evaluate this technique. Four, 3.1 by 3.1 m plots were identified and the shrubs within the plots were defoliated by hand-picking at about 10% intervals with imagery of the plots obtained between pickings. Imagery was obtained using a radio controlled airplane (drone) fitted with a 35 mm camera. Images were evaluated using image processing software and the resulting reflectance data correlated with defoliation percentages (weight basis) for each plot. Reflectance data from images correlated highly with defoliation percentages (r2 > 0.9). This technique of using LA/LS imagery shows promise for a quick and accurate tool in assessing utilization of shrubs.
    • Statistical analyses of fluorometry data from chloroform filtrate of lamb feces

      Mukherjee, A.; Anderson, D. M.; Daniel, D. L.; Murray, L. W.; Tisone, G.; Fredrickson, E. L.; Estell, R. E.; Rayson, G. D.; Havstad, K. M. (Society for Range Management, 2001-07-01)
      Accurately identifying the botanical composition of free-ranging animal diets remains a challenge. Currently accepted procedures are time consuming, many requiring painstaking sample preparation while none produce data useful for real-time management. Automated procedures focusing on detection of chemical and/or physical plant properties using specific molecules called fluorophores offers possibilities for determining the species composition of herbivore diets. This study was designed to evaluate fluorometry techniques in herbivore diet determinations using fecal samples obtained from 13 lambs fed a basal diet of tobosa hay (Pleuraphis mutica Buckley), and containing 4 different levels (0, 10, 20, and 30%) of tarbush (Flourensia cernua D C.) leaf material. Chloroform (CHCl3) filtrate obtained from the lamb's feces was exposed to UV light from a xenon arc lamp. This caused fluorophore molecules in the filtrate to have their outer shell electrons move to a higher energy state as a result of UV light excitation. After excitation by UV light at 310, 320, 330, 340, 350, and 355 nm, the fluorophores returned to their ground state giving off light (fluorescence). This fluorescence intensity (counts) varied and when captured using appropriate electronics, produced 1,024 pairs of light intensities (counts) and fluorescent wavelengths between 175 and 818 nm in 0.63 nm increments. Previous research indicated differences among diets could be determined using distinct peaks in the red and blue regions of the visible light spectrum and a univariate (1 variable at a time) analysis. This research demonstrates the entire fluorescence data set can be used to determine differences among diets using multivariate statistics. Sequences of 5 increasingly complex statistical techniques were used to distinguish among diets: 2-dimensional plots, polynomial regression models, confidence interval plots, discriminant analysis, and 3-dimensional plots. Two-dimensional plots indicated 2 spectral fluorescence peaks, 1 in the blue-green (420-600 nm) and 1 in the red (640-720 nm) region of the visible spectrum. Because of the asymmetrical nature of these peaks, fifth-order polynomials were developed to differentiate among the 4 diets. Statistical reliability was high when discriminating between diets containing no tarbush leaf and the diets containing 30% tarbush leaf; however, it was not possible to statistically separate diets containing intermediate (10 and 20%) amounts of tarbush leaf material from each other or from the 2 extremes (0 and 30% tarbush leaf). These results suggest spectral signatures arising from fluorometry data may be useful for differentiating among botanical composition diets that differ in plant form, but that a multivariate approach may require large sample sizes.
    • Restoring tallgrass prairie species mixtures on leafy spurge-infested rangeland

      Masters, R. A.; Beran, D. D.; Gaussoin, R. E. (Society for Range Management, 2001-07-01)
      Leafy spurge (Euphorbia esula L.) reduces northern Great Plains rangeland carrying capacity. Treatment strategies were evaluated that suppressed leafy spurge and facilitated establishment of mixtures of native grasses and legumes on range sites near Mason City and Tilden, Nebr. Glyphosate at 1,600 g a.i. (active ingredient) ha(-1) was applied with or without imazapic at 140 or 210 g a.i. ha(-1) in October 1995. In April 1996, standing crop was burned or mowed. Mixtures of native grasses [big bluestem (Andropogon gerardii Vitman), indiangrass (Sorghastrum nutans (L.) Nash), switchgrass (Panicum virgatum L.), little bluestem (Schizachyrium scoparium (Michx.) Nash), and sideoats grama (Bouteloua curtiplendula (Michx.) Torr.)] were then planted with or without native legumes [leadplant (Amorpha canescens (Nutt.) Pursh), Illinois bundleflower (Desmanthus illinoensis (Michx.) MacM.), and purple prairieclover (Petalostemum purpureum (Vent.) Rybd.)] at 440 pls m(-2) into a non-tilled seedbed. Imazapic was applied at 70 g a.i. ha(-1) in June 1996 to half the plots that had been treated with imazapic in October 1995. Frequency, dry matter yield, and leafy spurge density were measured 14 to 16 months after planting. Leafy spurge density and yield were least, and frequencies and yields of the planted grasses usually were greatest where imazapic had been applied with glyphosate in October 1995. Purple prairieclover was the only planted legume to persist 14 months after planting, and yields were greatest where imazapic was applied with glyphosate. Imazapic applied in June 1996 usually did not improve planted species yields or leafy spurge control. Total vegetation yields were greater where imazapic was applied with glyphosate at both sites and where native species were seeded at Mason City. Vegetation suppression with fall-applied herbicides and removal of standing crop enabled successful establishment of desirable species, increased forage yields, and suppressed leafy spurge.
    • Upland erosion under a simulated most damaging storm

      Linse, S. J.; Mergen, D. E.; Smith, J. L.; Trlica, M. J. (Society for Range Management, 2001-07-01)
      A 2 year study was conducted to determine the effects of surface cover and roughness on sediment yield from plots subjected to a simulated most damaging storm. This storm, based on long term sediment records from 3 Wyoming streams, produced approximately 18 mm of precipitation in 15 min with an intensity of 97 mm hour(-1). The rainfall simulator covered 2 plots; each 0.6 by 2 m. Plots were on 9% slopes with highly erosive soils (silt and fine sand texture) on native rangeland in 3 areas of Wyoming. Cover and surface roughness were measured with a point frame. Sediment production typically peaked approximately 120 sec after runoff started and reached steady state within 6 min. Plots with no cover (tilled) seldom produced runoff due to high infiltration and the short duration rainfall. Sediment yield was moderately correlated with total cover for total cover less than 30%, and sediment yield decreased to 0.1 tonnes ha(-1) (assumed allowable soil loss) or less for greater than 30% cover. There was a weak correlation between surface roughness and sediment yield, and surface roughness was slightly correlated with total cover. These results suggested that maintaining at least 30% total cover could control sediment yields from short duration-intense storms. Experimental results also indicated considerably higher sediment yields than those predicted by the Revised Universal Soil Loss Equation or a modified version of that equation.