• Does a Preharvest Application of Roundup® Improve Cotton Defoliation?

      McCloskey, William B.; Husman, Stephen H.; Silvertooth, Jeff; Department of Plant Sciences, University of Arizona, Tucson, Arizona; Cooperative Extension, Maricopa County, Phoenix, Arizona (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Preharvest applications of Roundup improved defoliation and regrowth suppression when used in conjunction with an application of Dropp +Def on Upland cotton in experiments conducted in Buckeye, Maricopa, and Queen Creek, AZ. However, all treatments used provided commercially acceptable defoliation. Preharvest Roundup applications made about two weeks (or one irrigation interval) before the application of Dropp +Def did not reduce seed cotton yields, lint yields, or affect color-grade and fiber characteristics.
    • The Interaction and Effects of Soil Moisture Regime and Yellow Nutsedge (Cyperus esculentus) Density on Cotton (Gossypium hirsutum) Growth

      Moffett, Jody E.; McCloskey, William B.; Husman, Stephen H.; Dixon, Gary L.; Silvertooth, Jeff; Department of Plant Sciences, University of Arizona, Tucson, Arizona; Cooperative Extension, Maricopa County, Phoenix, Arizona (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      The goal of our research is to determine the effects of yellow nutsedge competition on cotton and to examine how the competitive relationship between these two species is modulated by soil moisture. In support of this goal, a competition experiment with various nutsedge densities and three irrigation regimes was conducted at the University of Arizona, Maricopa Agricultural Center. The results of this study indicate that increasing nutsedge density caused a significant linear decrease in cotton seed yield in both 1993 (p=0.03) and 1994 (p=0.002). The cotton yield reductions caused by the highest nutsedge densities, 33 and 50 tubers /m of crop row in 1993 and 1994, respectively, were 13.5 and 15.5 percent, respectively. Stem biomass, an indicator of total above ground biomass, increased significantly with increasing soil moisture. There was also a trend of increasing seed cotton yield with increasing soil moisture with the wet treatment (i.e., irrigation at 35 percent soil moisture depletion) resulting in the highest biomass and yields. In 1994 this trend was significant (p=0.0001) but in 1993 it was not (p=0.098) probably because fewer replications were used in 1993. An important goal of this research was to determine if cotton, with its deeper tap root type of root architecture, is more competitive against yellow nutsedge, which has a fibrous root system, when irrigation is less frequent. However, analysis of variance showed that there was no significant interaction between soil moisture availability and seed cotton yield reductions caused by nutsedge competition in either 1993 (p=0.44) or 1994 (p=0.62).