• Alfalfa Tolerance to Norflurazon (Zorial 5G) on Coarse Textured Soils in Central Arizona

      McCloskey, William B.; Clay, Patricia A.; Ottman, Michael (College of Agriculture, University of Arizona (Tucson, AZ), 2000-10)
      The tolerance of seedling alfalfa to norflurazon applied at various times after planting was evaluated at the University of Arizona Maricopa Agricultural Center (MAC) and in Glendale, AZ during 1998 and 1999. At each application date, rates of 0, 1, 1.5, 2, 3, or 4 lbs a.i./A of norflurazon formulated as a 5% sand granule (Zorial 5G) were applied using a ground driven Valmar granule applicator. Zorial 5G at rates ranging from 1.5 to 4.0 lbs a.i./acre applied as early as 25 days after planting (DAP) had no effect on alfalfa seedling emergence and stand establishment at (MAC). Significant alfalfa height reductions were observed as Zorial 5G rate was increased when Zorial was applied at 25 and 62 DAP (MAC) and 64 DAP (Glendale). Alfalfa fresh weight yield for the MAC location was reduced at the second cutting after application as Zorial 5G rate increased for the at planting and 25 DAP treatments. Alfalfa yields approximately one year after planting were not affected by applications of Zorial 5G at 25 DAP or later. Results suggest that Zorial applications at rates of 1 to 2 lbs a.i./A applied at the 3 to 4 trifoliate leaf stage (approximately 2 months after planting) have little effect on yield at first and second cuttings of alfalfa.
    • Evaluation of Raptor 1AS and Other Herbicides for Sowthistle, Canarygrass, and Wild Oat Control in Alfalfa

      Rethwisch, Michael D.; Nelson John E.; Ottman, Michael (College of Agriculture, University of Arizona (Tucson, AZ), 2000-10)
      Two rates of Raptor herbicide were evaluated for late winter weed control in alfalfa in combination with various types of surfactancts, the insecticide Furadan, and other alfalfa herbicides with known limited control spectrums. Herbicides that were combined with Raptor were also evaluated separately, as was Pursuit. Effects of treatments on wild oats, littleseed canarygrass and annual sowthistle were obtained. Treatments containing the active ingredient clethodim (Select/Prism) reduced canarygrass height and reproduction, while Raptor treatments increased numbers of inflorescences. No treatment provided effective control of sowthistle although some activity was noted from the Raptor treatments when numbers of reproductive structures and height were examined. Surfactants/ adjuvants greatly increased Raptor activity. Wild oat control was noted in treatments containing clethodim and several Raptor treatments when utilizing a surfactant/adjuvant.
    • Response of Alfalfa Treatedwith Halosulfuron during the Summer of 1999

      McCloskey, William B.; Ottman, Michael (College of Agriculture, University of Arizona (Tucson, AZ), 2000-10)
      The response of alfalfa regrowth, yield and plant populations to halosulfuron applied following cuttings and irrigations in the summer and fall of 1999 was studied in an experiment conducted at the University of Arizona Maricopa Agricultural Center. A single application of halosulfuron applied when there was little alfalfa foliage slightly reduced plant heights for several cutting cycles with increasing rate decreasing plant height. The cumulative forage fresh weight yields for the October 4th, November 15th, and February 22nd harvests for treatments receiving no halosulfuron or 0.032, 0.047, or 0.063 lb a.i./A were (means ± std. dev.): 15.94 ± 0.91, 14.99 ± 0.66, 14.80 ± 1.74, and 14.46 ± 0.97 tons/A, respectively. The trend of decreasing cumulative forage fresh weight with increasing halosulfuron rate was significant (Adj. R2 = 0.178, P = 0.015) indicating that for the three harvests after August 25th, halosulfuron had a small but negative effect on forage fresh weight. The harvest on April 5, 2000, the fourth harvest following the halosulfuron applications on August 25, 1999, indicated that there was no longer any residual effect of halosulfuron on alfalfa growth. Plant populations measured on April 10, 2000 were not affected by either one or two halosulfuron applications in this experiment. A set of sequential halosulfuron treatments applied when there was substantial alfalfa foliage (about 80% of the ground surface covered) severely suppressed alfalfa regrowth. Little regrowth occurred in these plots in October or November after the sequential applications compared to the untreated control or to the plots that received only the initial application of halosulfuron. The change in mean percent yield loss with successive harvests on November 15th, February 22nd and April 5th of 85, 40 and 14% indicated that the alfalfa plants were recovering from the halosulfuron applications. The cumulative forage fresh weight yields for treatments receiving sequential halosulfuron treatments (0.032+0.032, 0.047+0.047, or 0.063+0.063 lb a.i./A) were (means ± std. dev.): 11.67 ± 1.46, 10.85 ± 1.06, and 10.44 ± 0.98 tons/A, respectively, and were much less than the cumulative yield of 18.97 ± 1.17 tons/A from the untreated plots. The data suggest that the critical factor in determining the degree of alfalfa injury caused by halosulfuron is the amount of foliage present at the time of application.