Now showing items 1-20 of 78034

    • Legitimacy Revisited: Disentangling Propriety, Validity, and Consensus

      Haack, Patrick; Schilke, Oliver; Zucker, Lynne; Univ Arizona (Wiley, 2020-08-15)
      Recent research has conceptualized legitimacy as a multi-level phenomenon comprising propriety and validity. Propriety refers to an individual evaluator's belief that a legitimacy object is appropriate for its social context, whereas validity denotes an institutionalized, collective-level perception of appropriateness. In this article, we refine this multi-level understanding of legitimacy by adding a third, meso-level construct of 'consensus', which we define as the agreement between evaluators' propriety beliefs. Importantly, validity and consensus are distinct and can be incongruent, given that an institutionalized perception can hide underlying disagreement. Disentangling validity from consensus is a crucial extension of the multi-level theory of legitimacy, because it enables an improved understanding of the legitimacy processes that precede sudden and unanticipated institutional change. In particular, while previous works considered revised propriety beliefs as the starting point for institutional change, our account emphasizes that the disclosure of the actual (vs. merely assumed) belief distribution within a social context may instigate institutional change. To study the interplay of propriety, validity, and consensus empirically, we propose a set of experimental designs specifically geared towards improving knowledge of the role of legitimacy and its components in institutional change.
    • Comparison of 3 techniques for monitoring use of western wheatgrass

      Halstead, L. E.; Howery, L. D.; Ruyle, G. B. (Society for Range Management, 2000-09-01)
      Forage use data can help rangeland and wildlife managers make informed decisions. However, managers need to know if forage use techniques that are commonly used to estimate ungulate herbivory under field conditions produce comparable results. The objective of this 2-year study was to directly compare forage use measurements obtained via the paired-plot method and 2 height-weight methods (using on-site height-weight curves and the pre-established United States Forest Service height-weight gauge). In June, July, and October of 1997 and 1998, we measured forage use of western wheatgrass (Pascopyrum smithii Rydb.) by cattle (Bos taurus L.) and wild ungulates, mainly elk (Cervus elaphus L.). On-site height-weight curves and the USFS gauge consistently produced lower estimates (overall means = 8 and 7%, respectively) than the paired-plot method (overall mean = 31%). Height-weight estimates did not differ (P > 0.05) when calculated with either on-site curves or the USFS gauge. Within sampling areas, paired-plot estimates were relatively more precise (mean CV = 63%) than on-site curves (mean CV = 238%) or the USFS gauge (mean CV = 271%). Selective grazing likely contributed to higher CVs for height-weight techniques. Our findings are important for rangeland and wildlife managers because the forage monitoring technique they use may influence the results obtained and, consequently, grazing management and wildlife harvest decisions. Managers should ensure that chosen monitoring techniques provide an appropriate evaluation of management goals and objectives.
    • Flow processes in a rangeland catchment in California

      Salve, R.; Tokunaga, T. K. (Society for Range Management, 2000-09-01)
      Emerging hydrology-related issues in California grasslands have directed attention towards the need to understand subsurface water flow within a complex, dynamic system. Tensiometers and neutron probes evaluated the subsurface hydrology of a rangeland catchment. Hydrological processes within the catchment varied both in space and time. Spatial variability was evident along the vertical profile and between the catchment slopes. Temporal variability in processes coincided with the seasons (i.e., wet winter, dry summer, and spring). From a water-balance equation developed for the catchment, we determined that there was significant variability both spatial and temporal in the amount of soil moisture lost to evapotranspiration and deep seepage. During the 16 month monitoring period there was a total of 50 cm of rainfall that fell in the catchment of which 9-55 cm was lost to evaporation and 37-79 cm to deep seepage. A simple deduction of the losses (evaporation and deep seepage) from the input (rainfall) shows that all monitored locations had a substantial decrease in the amount of water that was stored in the soil profile.
    • Rotational stocking and production of Italian ryegrass on Argentinean rangelands

      Jacobo, E. J.; Rodriguez, A. M.; Rossi, J. L.; Salgado, L. P.; Deregibus, V. A. (Society for Range Management, 2000-09-01)
      The decreased carrying capacity of Argentinian Flooding Pampa rangelands through the reduction of density of C3 grasses may be partially attributed to continuous stocking. The objective of this study was to evaluated the effectiveness of rotational vs. continuous stocking to improve winter forage production by incrementing the density of Italian ryegrass (Lolium multiflorum Lam.). Under rotational stocking, ryegrass seedlings established almost 2 months earlier in the fall and tiller density was 3-fold higher in winter than under continuous stocking. Aerial net primary productivity of C3 grasses was approximately 2-fold greater under rotational compared with continuous stocking in the first and second years. This substantial increase in winter productivity supported almost 2-fold increase in stocking rate (from 0.6 to 1.0 AU ha-1).
    • Effects of roundups on behavior and reproduction of feral horses

      Hansen, K. V.; Mosley, J. C. (Society for Range Management, 2000-09-01)
      Roundups are used to maintain feral horse populations in balance with rangeland grazing capacity, but little is known about short-term and long-term effects of roundups on horses. We evaluated the effects of roundups on behavior and reproduction of feral horses. The study was conducted near Challis, Ida. during 1994-1995, and repeated near Lander, Wyo. during 1995-1996. Horses were randomly assigned to 3 different treatment groups. One group (ADOPTED) was gathered by a Bureau of Land Management roundup crew using a helicopter. These horses were removed and placed in the Adopt-A-Horse Program. The second group (SIMULATED) consisted of horses that were gathered by helicopter, but these horses evaded capture and remained in the study area after the roundup. Horses in the third group (CONTROL) were not herded by helicopter. Horse behavior was monitored in the SIMULATED and CONTROL groups before and after roundups. Behavioral variables analyzed were the percentage of time spent resting, feeding, vigilant, traveling, and engaged in agonistic encounters. Neither foraging or social behavior of feral horses was affected by roundups in either study area (P > 0.10). Reproduction was monitored within the SIMULATED, CONTROL, and ADOPTED groups during the year following roundups. The percentages of mares with live foals did not differ (P > 0.10) among the 3 treatment groups in Idaho or Wyoming. Foaling success rates in Idaho were 29%, 31%, and 43% for CONTROL, ADOPTED, and SIMULATED mares, respectively. In Wyoming, foaling success rates were 29%, 42%, and 48% for CONTROL, ADOPTED, and SIMULATED groups, respectively. We found no evidence that roundups had deleterious effects on behavior or reproduction of feral horses.
    • Vegetation response to stocking rate in southern mixed-grass prairie

      Gillen, R. L.; Eckroat, J. A.; McCollum, F. T. (Society for Range Management, 2000-09-01)
      Stocking rate directly influences the frequency and intensity of defoliation of individual plants which, in turn, impacts energy flow and plant succession in grazed ecosystems. The objective of this study was to determine the effect of stocking rate on standing crop dynamics and plant species composition of a southern mixed-grass prairie over a 7-year period (1990 through 1996). Long-term (30-year) mean precipitation has been 766 mm per year. Growing conditions were generally favorable for the study period. Yearling cattle (initial weight 216 kg, SD = 12 kg) grazed at 6 stocking rates, ranging from 23 to 51 AUD ha-1, from 14 April to 24 September (162 days). The currently suggested year-long stocking rate is 25 AUD ha-1. Herbage standing crop was measured in July and September every year while species composition was determined in July in even years. Total and dead standing crop declined as stocking rate increased but live standing crop was not related to stocking rate. Slopes of regression lines relating standing crop and stocking rate were constant over years, indicating no response for plant productivity. The major vegetation components, sideoats grama [Bouteloua curtipendula (Mich.) Torr.], shortgrasses, and forbs were not affected by stocking rate over years. Tallgrasses responded by increasing at the lower stocking rates over the study period. However, these grasses contributed less than 5% of the total standing crop. Red and purple threeawn (Aristida longiseta Steud. and A. purpurea Nutt.) increased at all stocking rates from 1990 to 1996 but the increase was greater at the lower stocking rates. This mixed-grass vegetation showed little response to stocking rate over the 7-year study period. The vegetation may have been in equilibrium with previous heavy stocking rates so that little change would be expected at those rates. Increases in grazing sensitive species at lighter stocking rates may occur over longer time intervals.
    • Grazing impacts on selected soil parameters under short-term forage sequences

      Mapfumo, E.; Chanasyk, D. S.; Baron, V. S.; Naeth, M. A. (Society for Range Management, 2000-09-01)
      Long-term cultivation is known to change soil physical and chemical properties, but little is known about whether short-term agricultural practices, such as rotational grazing, can initiate such changes. This study investigated the impacts of 3 grazing intensities (heavy, medium, and light) and 4 forages on selected soil physical and chemical parameters of a Typic Haplustoll at Lacombe, Alberta. Measurements were conducted on soil samples collected at the beginning (1993) and the end (1996) of the study. Two perennial forages, smooth bromegrass (Bromus inermis cv. 'Carlton') and meadow bromegrass (Bromus riparius cv. 'Paddock'), and 2 annuals, a mixture of triticale (X Triticosecale Wittmack cv. 'Pika') and barley (Hordeum vulgare L. cv. 'AC Lacombe') and triticale alone were used for the study. Grazing intensity or forage species did not affect carbon-to-nitrogen ratio. Grazing intensity influenced changes in available water holding capacity for the 0-5 cm interval, soil nitrogen for the 30-45 cm interval, soil pH for the 5-15 cm interval and electrical conductivity for all depth intervals except for the 0-5 cm interval (P less than or equal to 0.05). Forage species affected changes in soil carbon in the 0-5 cm interval, soil pH between 0 and 15 cm, and electrical conductivity between 5 and 45 cm (P less than or equal to 0.05). Soil electrical conductivities for all grazing levels and forage treatments were within the range (i.e. 0-2 dS m-1) considered to have negligible effects on plant growth. The minimal effects of grazing and plant species on soil parameters in this study may have been due to the resilient intrinsic properties of the soil and/or the short study length.
    • A comparison of soil chemical characteristics in modified rangeland communities

      Dormaar, J. F.; Willms, W. D. (Society for Range Management, 2000-07-01)
      The effects of converting native prairie to simplified agronomic communities on primary production and soil quality are expected to differ over the short-term. A study was initiated at 4 locations: a Mixed Prairie with Stipa comata Trin. Rupr. dominant in the Brown Soil Zone (1994), a Mixed Prairie with S. comata and S. viridula Trin. dominant in the Dark Brown Soil Zone (1993), and 2 in the Fescue Prairie with Festuca campestris Rydb. dominant in the Black Soil Zone (1993). At each of the 4 sites, 5 treatments representing common production systems were seeded as monocultures [2 grass species, alfalfa (Medicago sativa L. 'Beaver'), and 2 spring wheat (Triticum aestivum L. 'Katepwa) seeded as either continuous or as wheat-fallow], and 1 treatment consisting of abandoned cultivation were compared with a native community in a randomized complete block design with 4 replicates. One site in the Black Soil Zone was an overgrazed prairie (2.4 animal unit month ha-1 since 1949) and a second was mostly ungrazed for the previous 50 years with occasional light fall-grazing. Soils of the modified communities were different (P < 0.05) than of the native community with respect to percent carbon and nitrogen, concentration of monosaccharides, and concentration of most phosphorus constituents. Modifying the community through cultivation and seeding usually caused a reduction in the measured variable except for NaHCO3 inorganic phosphorus that increased. Cultivation rather than the plants of the new community was believed responsible for most of the observed changes in C, N, and various P fractions and the loss of water-stable aggregates remaining on the 2.0 and 1.0 mm sieves. Although the contribution of seeded species on the chemical and physical characteristics would not have been significantly expressed in 2 to 3 years and many more years would be required to reach a steady state, monosaccharide distribution had nevertheless started to shift to one that was plant-affected.
    • Plant Establishment on Angle of Repose Mine Waste Dumps

      Nowak, Robert S. (Society for Range Management, 2000-07-01)
      Angle of repose slopes associated with mine waste dumps are difficult to revegetate due to steep slope angle, poor soil properties, and potential for extensive soil erosion. We examined the extent that seed movement, seedling establishment, soil characteristics, nutrient availability, and water availability were responsible for limiting plant establishment or survival on steep (average slope ~80%), south-facing angle of repose slopes at a gold mine north of Elko, Nev. Four treatments were established: 1) unaltered mine waste soil; 2) mine waste soil with fertilizer; 3) mine waste soil draped with at least 0.3 m of a fine-textured coversoil; and 4) treatments 2 and 3 combined. All treatments had study plots that received either broadcast seeds or containerized transplants. Seedlings from broadcast seeds only emerged on plots that were coversoiled, but transplants survived in all treatments. Thus, coversoiling was necessary at this site for seedling germination and establishment, but survival of transplants in unaltered mine waste soil indicated that nutrient availability, soil-root contact, and water availability were sufficient for plant survival. In addition, long distance transport of seeds down stable, angle of repose slopes was not detected during the first growing season after seeding, indicating that the lack of seedlings on angle of repose slopes was not due to movement of seeds down-slope. However, coversoiling resulted in unstable slope surfaces; both erosion and soil mass wastage were observed on coversoiled treatments. Thus, although coversoiling increased establishment and survival of plants on angle of repose slopes, slope stabilization is necessary to ensure the success of revegetation efforts and to prevent the coversoil from eroding and moving downslope.
    • Grass response to seasonal burns in experimental plantings

      Howe, H. F. (Society for Range Management, 2000-07-01)
      A 6-year experiment examined the effects of spring and summer fires on grasses in southern Wisconsin. Synthetic communities of C3 and C4 grasses were seeded (100 seeds m-2 species-1) in 1992 and subjected to prescribed burns in May and August of 1995 and 1997, or left unburned. By 1994 all plots were virtual monocultures of the C3 reed canary grass (Phalaris arundinacea L.). By the second post-season sample in 1998, total productivity of plots burned in May was higher (781 +/- 212 se g m-2 year-1) than those burned in August (362 +/- 28 g m-2 year-1) or left unburned (262 +/- 43 g m-2 year-1) due to the incursions of either the C4 grasses big bluestem (Andropogon gerardii Vitman), switchgrass (Panicum virgatum L), or both. These large late-season grasses are much more productive per area covered than P. arundinacea or the other two C3 grasses present, Elymus virginicus L. and Poa pratensis L. Even at this early stage of succession, C4 production in plots burned in May was 5 to 6 times that in the other 2 treatments. August burns produced a mix of C3 and C4 grasses but did not strongly favor the pre-treatment C3 dominant P. arundinacea. Unburned plots most resembled those burned in August in species composition, but differed in having 4 times the accumulated litter, perhaps foretelling divergence in C3 and C4 composition as succession proceeds.
    • Rearing conditions for lambs may increase tansy ragwort grazing

      Sutherland, R. D.; Betteridge, K.; Fordham, R. A.; Stafford, K. J.; Costall, D. A. (Society for Range Management, 2000-07-01)
      Grazing by sheep is an accepted method of controlling tansy ragwort (Senecio jacobaea L.), but some flock members seldom eat it. Our objectives were to determine if pre-weaning exposure to tansy ragwort increases later consumption of the plant by lambs, and if confinement with ragwort-eating ewes after weaning facilitates ragwort eating. The sampling periods were Weeks 1, 3, and 12 following weaning. During each period grazing behavior was observed for 1-hour each day and the 24-hour reduction in ragwort volume measured on each of 4 or 5 consecutive days. Lambs exposed to ragwort before weaning removed more ragwort than ragwort-naive lambs during the first 2 sampling periods (P < 0.05). Lambs that grazed with ewes for 11 weeks following weaning ate ragwort more frequently during direct observation, than lambs without ewes during Weeks 3 and 12 (P < 0.05). The ragwort-eating of all lamb groups increased markedly between Weeks 1 and 12 (P < 0.05). This may indicate an increased ability of lambs to consume ragwort with increasing age or an acclimation period during which most lambs come to accept ragwort. Behavioral interventions aimed at increasing the consumption of weeds by lambs may need to take into account age-related differences in toxin tolerances. Exposing lambs to ragwort before weaning and grazing newly-weaned lambs with older ragwort-eating sheep after weaning may increase later ragwort-eating by lambs.
    • Cattle prefer endophyte-free robust needlegrass

      Jones, T. A.; Ralphs, M. H.; Gardner, D. R.; Chatterton, N. J. (Society for Range Management, 2000-07-01)
      Robust needlegrass (Achnatherum robustum [Vasey] Barkw. = Stipa robusta [Vasey] Scribn.) is a high-biomass rangeland species that is adapted to warmer temperatures and matures later than most cool-season grasses. However, it has been associated with negative animal effects including avoidance. We compared populations of Neotyphodium and P-endophyte-infected endophyte-infected (E+) and endophyte-free (E-) robust needle-grass for animal preference. Leaf blades were fed to yearling heifers in 3 trials of 8-min cafeteria sessions for 4 to 5 days each. Trial 1 (27-30 May) compared E+, E-, basin wildrye (Leymus cinereus [Scribn. Merr.] A. Löve), and tall wheatgrass (Thinopyrum ponticum [Podp.] Barkw. D.R. Dewey). Basin wildrye consumption (425 g) did not differ from tall wheatgrass (342 g), but basin wildrye consumption exceeded E- (258 g), which in turn exceeded E+ (117 g) (16 animal-sessions). Basin wildrye was dropped from Trial 2 because its consumption exceeded that of both E- and E+. In Trial 2 (1-5 June), consumption of E-, E+, and tall wheatgrass did not differ. Tall wheatgrass was dropped from Trial 3 to allow direct comparison of E- and E+. In Trial 3 (13-17 July), consumption of E- (585 g) exceeded E+ (145 g) (15 animal-sessions). In Trial 3, animals often rejected E+ forage before tasting. Discrimination against E+ was greater at the end of Trial 3 than at the beginning. The reputation of robust needlegrass for animal avoidance may be more related to its endophyte infection status than to the grass itself. Differences in forage-quality parameters were not large enough to account for the observed differences in preference. Ergot and loline alkaloids were not found in either E- or E+, therefore they cannot be responsible for the observed avoidance of E+. Non-trace amounts of ergot alkaloids were found only in seed collected in the Sacramento Mountains of New Mexico and not at other locations in New Mexico, Arizona, or Colorado.
    • Vegetation response to late growing-season wildfire on Nebraska Sandhills rangeland

      Volesky, J. D.; Connot, S. B. (Society for Range Management, 2000-07-01)
      This study examined the effects of late growing-season (September) wildfire on the subsequent production and species composition of upland Nebraska Sandhills prairie vegetation. Three paired-plots (burn and control), 0.5 ha in size were established in 1995 on sands range sites on each of 3 replications in west-central Nebraska. Soil temperature data were collected the following growing season and herbage standing crop and species composition data were collected for 3 growing seasons following the burn. During March through May of the 1996 growing season, soil temperature in the burn treatment was an average of 1.6 degrees C higher at both 15 and 30 cm depths compared to the control (P < 0.05). This small increase in spring soil temperature under the burn treatment did not appear to result in earlier growth or to increase herbage standing crop in May. Total herbage standing crop in August averaged 143, 142, and 185 g m-2 in 1996, 1997, and 1998, respectively, and did not differ between the burn treatment and control (P > 0.05). Little bluestem [Schizchyrium scoparium (Michx.) Nash] was the species most adversely affected by burning. Percentage composition by weight of little bluestem in August 1996 averaged 8% under the burn treatment compared to 47% in the control. Other species and species groups, however, were more abundant in burned plots, thus offsetting the lesser amounts of little bluestem. Little bluestem exhibited a marked recovery during the second and third growing seasons after the burn. During the third growing season, percent composition of little bluestem averaged 46% and was not different between treatments (P > 0.05). Forbs were more abundant under the burn treatment compared to the control only during the first growing season following the burn (P < 0.05).
    • Supplemental barley and charcoal increase intake of sagebrush by lambs

      Banner, R. E.; Rogosic, J.; Burritt, E. A.; Provenza, F. D. (Society for Range Management, 2000-07-01)
      We evaluated the influence of supplemental barley and activated charcoal on the intake of sagebrush by lambs in individual pens. In 3 experiments, lambs were fed sagebrush (harvested and chopped to 2-3 cm) during the morning; they were fed a basal diet of alfalfa pellets in the afternoon. In the first experiment, lambs supplemented with activated charcoal + barley ate more A. tridentata ssp. vaseyana than lambs supplemented with barley (304 vs. 248 g; P = .071). A second set of experiments, which consisted of 3 trials, determined the effects of activated charcoal, barley, and subspecies of sagebrush on intake of sagebrush. Lambs supplemented with activated charcoal + barley ate more A. tridentata ssp. vaseyana (Trial 1; 292 vs. 225 g; P = .086), and more A. tridentata ssp. tridentata (Trial 2; 371 vs. 255 g; P = .031) than lambs supplemented with barley. In Trial 3, lambs supplemented with barley ate more sagebrush than lambs that were not supplemented (480 vs. 318 g; P = .0002). A third set of experiments compared activated charcoal + barley, barley, and no supplement in 2 trials. In Trial 1, lambs supplemented with activated charcoal + barley or barley generally ate more A. tridentata ssp. vaseyana than lambs not supplemented (P = .017). In Trial 2, lambs supplemented with activated charcoal + barley ate slightly more A. tridentata ssp. vaseyana than lambs supplemented with barley, and they ate substantially more than lambs not supplemented (P = .032). Collectively, the results suggest that energy from supplemental barley increased intake of sagebrush by lambs fed a basal ration of alfalfa pellets which are high in protein, and that activated charcoal played a minor role in further increasing intake of sagebrush.
    • N and P fertilization on rangeland production in Midwest Argentina

      Guevara, J. C.; Stasi, C. R.; Estevez, O. R.; Le Houérou, H. N. (Society for Range Management, 2000-07-01)
      Low soil nutrient status may be the major limiting factor to forage production in rangelands of the Mendoza plains 4 years out of 10. We studied vegetation responses to annual applications of N and P on such rangelands. Fertilizer application rates were 0 or 25 N and 0 or 11 P (kg ha-1) in a factorial arrangement. Dry matter production of grasses and palatable shrubs and crude protein (CP) content of grasses were determined annually from 1996 to 1998. Experimental plots received rains of 189, 278, and 346 mm during the 3 study years compared to mean growing season rainfall of 258 mm. Forage production was increased by N+P fertilization only in 1998 (1,390 vs 980 kg ha-1, P 0.05), producing 16.5 kg forage kg-1 N applied. Crude protein concentration was increased by N fertilization in 1997 (6.3 vs 5.3%, P < 0.05) and N+P application increased in 1998 (6.8 vs 5.7%, P < 0.05). Nitrogen and P application increased seasonal rain-use efficiency when the rainfall exceeded 300 mm. In 1998, the increase of grass production per kg N applied with and without P was 18.4 and 12.4 kg, respectively. The break-even point between rain and nutrients as the main primary production determinant on sandy soils in the central Mendoza plains is around 400 mm year-1 instead of 300 mm in other arid lands of the world. The value of meat increment derived from the N fertilization, with and without P application (US 0.07 ha-1 year-1 kg-1 N) was lower than the fertilizer cost (US 0.87 kg-1 N). A 5-fold increase in forage yields would be required to offset the cost of fertilizer. Fertilizer application did not increase forage production enough to be profitable for cattle production at present fertilizer and meat prices.
    • Hydrologic responses of shortgrass prairie ecosystems

      Weltz, L.; Frasier, G.; Weltz, M. (Society for Range Management, 2000-07-01)
      Runoff hydrographs from 3 separate rainfall simulation runs at 11 different shortgrass prairie sites were evaluated to determine the hydrologic similarity within a single ecosystem at widely separated sites. There were no consistent patterns in the equilibrium runoff among sites and simulator runs. When the sites were stratified by soil type, there were differences in time-to-peak of the runoff event and the regression slope of the rising limb of the runoff ratios. Spearman's rank correlation showed no relation of the rising limb slope regression coefficient to measured vegetative characteristics across all sites. There was minimal correlation between the runoff regression coefficient and the percent cover and bare soil. Differences in the biotic components of the sites were not useful in predicting runoff characteristics. If equilibrium runoff was the measured hydrologic response, the sites were dissimilar. Using the time-to-peak and slope of the rising limb components of the runoff hydrograph, the sites were similar on the same soil type. The technique of comparing components of the runoff hydrograph, other than equilibrium runoff has promise to allow one to quickly compare responses among ecosystems to determine if they have similar hydrological functions. Our study on shortgrass prairie sites indicated that easily estimated factors such as biomass, cover and litter were not good indicators of hydrologic function. Also, it is necessary to identify which portion of the runoff event is most important in the assessment. Future hydrologic and erosion models need to develop nonlinear prediction equations to estimate infiltration rates as a function of cover, biomass, and soil properties and also to stratify soils into functional units to accurately estimate runoff rates.
    • Herbage volume per animal: A tool for rotational grazing management

      Duru, M.; Ducrocq, H.; Bossuet, L. (Society for Range Management, 2000-07-01)
      The objective of this study was to provide a tool for maintaining a high grazing efficiency. In a rotational grazing system, the residual sward height does not provide enough information in advance to make the recommendation. The grazing management of 4 commercial dairy farms which differed greatly in their stocking rate, was monitored over 3 spring seasons. Data were collected on the overall grazing area (sward height measurements, stocking rate, indoor feeding, nitrogen supply) and on 3 grazed fields (herbage mass, height, and nitrogen status). At the whole grazing area level, computed data were herbage volume per animal unit (HVAU). We show that the HVAU depends on the residual herbage height. Both criteria decreased when stocking rate increased. The HVAU reflects, at the whole grazing season and area levels, how the system works on grazed field over grazing cycle. The HVAU has 2 advantages: (i) It gives rough estimation of the size of the whole grazing area to achieve a high grazing efficiency; (ii) it is a means to assess a posteriori the efficiency of the grazing system regarding the consistency between stocking rate and nitrogen supply management.
    • Evaluating breeding seasons for cows grazing winter range and bahiagrass

      Pate, F.; Kalmbacher, R.; Martin, F. (Society for Range Management, 2000-07-01)
      Florida native range is grazed in winter and cows are moved to bahiagrass (Paspalum notatum Flugge) pasture in March for breeding and calf rearing. Winter weight loss of cows is a major problem, and one possibility to reduce it is to alter the breeding season. This 4-year study evaluated October-February range grazing with movement of cows to bahiagrass in late February for breeding and calf rearing beginning in March (spring-bred cows) vs. December-April range grazing with movement of cows to bahiagrass in May (summer-bred cows). Spring-bred cows weighed less coming off range (439 kg) than summer-bred cows (459 kg), but spring-bred cows gained more weight on bahiagrass (38 kg) by the time calves were weaned than summer-bred cows (1 kg). At weaning, there were no differences in weights of cows. Weight loss of cows on range was related to weight going onto range in the fall (r = -0.62 and -0.49 for spring- and summer-bred cows). Declining nutritive value of bahiagrass and heavy rains in the late summer and early fall appeared to lead to the inability of summer-bred cows to regain weight on bahiagrass. In 2 years, rain interfered with range burning in October which was needed to improve the palatability and nutritive value of forages for spring-bred cows, but this appeared to have no effect on cow performance. Weaning weight of calves from the spring-bred cows (205 kg) tended to be higher than that of calves from summer-bred cows (181 kg). There were no differences in pregnancy rates (74.5%). A March-May breeding season is recommended over a May-July breeding season for cows using a combination of range and bahiagrass.
    • Fire and cattle grazing on wintering sparrows in Arizona grasslands

      Gordon, C. E. (Society for Range Management, 2000-07-01)
      This paper reports on the results of a 3-year field study of the effects of spring/summer burning and cattle grazing on wintering sparrows in the grasslands of southeastern Arizona. The effects of fire were studied with 1 year of pre-burn data and 1 year of post-burn data from 1 fire, plus limited sampling from a second fire at Buenos Aires National Wildlife Refuge in Pima County, Ariz. The effects of grazing were studied by comparing study plots at a site that has not been grazed by cattle since 1968 with a nearby grazed pasture in Santa Cruz County, Ariz. Sparrow abundance was measured as the number of captures from flush-netting sessions conducted by groups of 13-30 volunteers. Vesper (Pocecetes gramineus (Gmelin)) and Savannah (Passerculus sandwichensis (Gmelin)) Sparrows responded positively to fire, while Cassin's Sparrows (Aimophila cassinhi (Woodhouse)) responded negatively. The ecologically and geographically restricted Baird's (Ammodramus bairdil (Audubon)) and Grasshopper (A. savannarum (Gmelin)) Sparrows utilized burned areas during the first post-burn winter and did not significantly respond to fire. Both Ammodramus sparrows also utilized the grazed pasture; they were more abundant there than in the ungrazed study area in 1 year. While field observations and a prior study suggest that heavy grazing can have a strong detrimental effect on Ammodramus sparrows, the results of this study suggest that moderate cattle grazing may be compatible with the conservation of these species.
    • Perceptions and economic losses from locoweed in north-eastern New Mexico

      Torell, L. A.; Owen, L. P.; McDaniel, K. C.; Graham, D. (Society for Range Management, 2000-07-01)
      Livestock producers and others knowledgeable about the locoweed problem in northeastern New Mexico were surveyed to obtain the production information needed to estimate economic losses from locoweed (Oxytropis/Astragalus) poisoning. A partial budgeting approach was used to estimate economic losses based on animal performance differences with increasing levels of poisoning. With current production costs and 1990-96 average beef prices, annual locoweed poisoning losses were estimated to be 75 head-1 for moderately poisoned animals, and 282 head-1 for severely poisoned animals. The most common locoweed management strategy used by northeastern New Mexico ranchers was to move animals observed eating locoweed into locoweed-free areas. Rehabilitation of these animals for an extended period before sale was found to decrease economic loss relative to immediate sale. Moderately and severely poisoned animals that are rehabilitated were estimated to gain 14% and 29% less than non-intoxicated animals. Other management options including chemical locoweed control, fencing, and locoweed aversion were found to be economically justified when relatively high locoweed infestations are anticipated.