• Herbage characteristics and performance of steers grazing old world bluestem

      Coleman, S. W.; Forbes, T. D. A. (Society for Range Management, 1998-07-01)
      Old World bluestem (OWB; Bothriocloa spp.) are popular in the southern Great Plains but little is known about the relationships between forage characteristics and animal productivity. The influence of differences in herbage mass and sward height of OWB on rate of gain during the summer grazing season was examined during 2 years at El Reno, Okla. Soils were fine, silty Pachic Haplustolls of the Dale series. Swards of caucasian [B. caucasica (Trin.) C. E. Hubb.] and 'Plains' [B. ischaemum var ischaemum (L.) Keng.] OWB were maintained at different levels of forage mass (low, medium, and high) by continuous variable stocking and were grazed from mid- May to late September by steers with an initial weight of about 225 kg. Weight gains were depressed in late August, but in 1985 gains recovered due to late season rains. Season-long gains averaged 0.61 kg day-1 in 1984 and 0.69 kg day-1 in 1985. Daily gains of steers increased linearly with increased herbage mass (P < 0.05), but slopes were different due to a year X species interaction. Daily gains peaked at a herbage height of 41 cm in 1984, but increased linearly throughout the range of the data (75 cm) in 1985. Individual animal gains decreased linearly with increasing stocking rate such that maximum gain per hectare was achieved at about 5 animals ha-1 (standard 500 kg). The data suggest that maintaining higher herbage mass and height of OWB forage improves animal performance and support the practice of intensive early grazing and removing cattle by late July when rate of gain declines.
    • Morphological development of 2 warm-season grasses in the Nebraska Sandhills

      Hendrickson, J. R.; Moser, L. E.; Moore, K. J.; Waller, S. S. (Society for Range Management, 1998-07-01)
      Morphological development of grasses has numerous implications to rangeland management including the timing and amount of herbivory. The objective of this study was to quantify the developmental morphology of prairie sandreed [Calamovilfa longifolia (Hook.) Scribn.] and sand bluestem [Andropogon gerardii var. paucipilus (Nash) Fern.] tiller populations. Tiller populations of these 2 grasses were studied for 2 years in the Nebraska Sandhills. Plant development was evaluated using a growth staging system which quantifies the development of tiller populations. A morphological growth index for each species was calculated from either the weighted average of tiller numbers reported as mean stage count (MSC) or tiller weight reported as mean stage weight (MSW) and correlated with the independent variables of growing degree days (GDD) and day of year (DOY). Correlation coefficients with the independent variables were greater than 0.97 for MSC and MSW within years and greater than 0.90 between years. Greater rainfall and warmer temperatures in 1991 increased the number of tillers in the more advanced morphological stages in prairie sandreed, but tiller weight rather than tiller number increased in more advanced stages of sand bluestem. A majority of the harvested tillers were vegetative throughout the sampling period but by the end of the growing season, a wide range of morphological stages were present. The use of grazing to prevent the formation of culmed tillers in these grasses may be unnecessary because of the high proportion of vegetative tillers and the wide range of morphological stages available for selection by livestock.
    • Nitrogen fertilization, botanical composition and biomass production on mixed-grass rangeland

      Samuel, M. J.; Hart, R. H. (Society for Range Management, 1998-07-01)
      Many studies have reported nitrogen (N) fertilization of rangeland, but few have reported changes in botanical composition, which may be as important as changes in forage production, or were continued for as long as 14 years. We determined frequency of occurrence of over 90 plant species in 1976-1988 under rates of 0, 22, or 34 kg N ha-1 applied in spring or fall to mixed-grass rangeland in southeast Wyoming; frequency of 23 species will be reported. We also determined total biomass production and production of major species and species groups in 1982-1988. Blue grama Bouteloua gracilis (H.B.K.) Griffiths] frequency decreased during years 5 through 7 because of the interaction of N and drought. The effects of long-term application of N decreased blue grama in year 12 and beyond. Nitrogen fertilization increased frequency of western wheatgrass [Pascopyrum smithii (Rydb.) A. Love] in all years except the driest year of the study. Needleleaf sedge [Carex eleocharis Bailey] decreased because grazing had been removed from the study area; this occurred sooner and to a greater extent on fertilized than on unfertilized plots. Fourteen other perennial species were quite variable in response to the 3 rates and the 2 seasons of application. Frequency of 6 annual species fluctuated greatly among years and treatments. Nitrogen fertilization did not increase average forage production enough to be profitable for cattle production.