• Long term change in vegetation following herbicide control of larkspur

      Ralphs, M. H. (Society for Range Management, 1995-09-01)
      Larkspur (Delphinium spp.) control can reduce cattle deaths on mountain rangelands, but vegetation cover must be maintained to protect watersheds from erosion. The objective of this study was to evaluate the long term impact of herbicides on larkspur control and cover of associated species. Duncecap larkspur (Delphinium occidentale S. Watts) near Oakley Ida., and tall larkspur (D. barbeyi Huth) near Manti Utah, were the target species. Picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid) was applied at 1.1, 2.2, and 4.5 kg ae/ha; glyphosate (N-(phosphonomethyl)glycine) was applied at 0.06, 1.1, and 2.2 kg ai/ha; and metsulfuron (1-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amine]carbonyl ]amino]sulfonyl]benzoic acid) was applied at 0.035, 0.07, and 0.14 kg ai/ha. Picloram at 2.2 kg/ha maintained long-term control of both larkspur species (> 80%) when applied in the vegetative, bud, and flower growth stages. Total grass cover was higher on picloram plots than other treatments. Forb cover declined and bare ground was greater in picloram plots than other treatments at Manti. Metsulfuron controlled duncecap larkspur when applied in the vegetative stage. However, long-term control of tall larkspur at Manti declined as new tall larkspur seedlings established. Glyphosate controlled both larkspurs when applied in the vegetative and bud stages, but it allowed undesirable annual and rhizomatous forbs and shrubs to increase by the end of the study. Grass cover was lower on glyphosate plots than on other treatments. Bare ground was higher on glyphosate plots than other treatments at Oakley, but was intermediate at Manti.
    • Nitrogen fertilizer use efficiency in steer gain on old world bluestem

      Berg, W. A.; Sims, P. L. (Society for Range Management, 1995-09-01)
      Old World bluestem (Bothriochloa ischaemum L.) is the major grass being planted for improved pastures on marginal farmland in western Oklahoma and adjacent areas in Texas. The farmland is often deficient in plant available N as a result of up to 100 years of cultivation and erosion. This study determined N fertilizer use efficiency on steer gain when grazing Old World bluestem in northwestern Oklahoma where average annual precipitation is 575 mm yr(-1). The study was conducted over 4 summer grazing seasons on Pratt soils (sandy, mixed thermic Psammentic Haplusalfs). Nitrogen rates of 0, 34, 68, and 102 kg N ha(-1) yr(-1) were applied to paddocks in a randomized complete block design with 4 blocks. Steer gain averaged 220 kg ha(-1) yr (-1) and 3.3 kg per kg N applied at the 34 kg N ha(-1) yr(-1) rate. Steer gain ranged from 2.3 to 4.3 kg yr(-1) per kg of N applied at the rate of 34 kg N ha(-1) yr(1). About an additional kg of steer gain per kg N applied was realized for the second 34 kg N ha(-1) yr(-1) increment from 34 to 68 kg N ha(-1)yr(-1). Gain was negligible from the third 34 kg N ha(-1) yr(-1) increment from 68 to 102 kg N ha(-1)yr(-1). Early summer grazing of N-fertilized Old World bluestem has high stocker production potential.