• Reduced Tillage Effects on Irrigation Management in Cotton

      Martin, E. C.; Adu-Tutu, K. O.; McCloskey, W. B.; Husman, S. H.; Clay, P.; Ottman, M.; University of Arizona, Tucson, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 2003-05)
      Conservation or reduced tillage practices in cotton-based crop rotation systems were studied in field experiments initiated at Marana, Coolidge and Goodyear in 2001. Following barley cover and grain crops, soil and water management assessments were made during the 2002 cotton season at the three sites. Cover and grain crop residues and a lack of tillage prior to planting cotton or during the cotton season increased the infiltration of irrigation water into coarsetextured soils, slowed irrigation advance times, and increased the amount of irrigation water used at two of the three sites compared to conventional tillage treatments.
    • Residual Soil Nitrogen Evaluations in Irrigated Desert Soils, 2002

      Silvertooth, J. C.; Galadima, A.; Norton, E. R. (College of Agriculture, University of Arizona (Tucson, AZ), 2003-05)
      Field experiments investigating N fertilizer management in irrigated cotton production have been conducted for the past 15 seasons at three Arizona locations on University of Arizona Agricultural Centers (Maricopa, MAC; Marana, MAR; and Safford, SAC). In 2002, residual N studies were conducted at two of these locations (MAC and MAR). The MAC and SAC experiments have been conducted each season since 1989 and the Marana site was initiated in 1994. The original purposes of the experiments were to test nitrogen (N) fertilization strategies and to validate and refine N fertilization recommendations for Upland (Gossypium hirsutum L.) and American Pima (G. barbadense L.) cotton. The experiments have each utilized N management tools such as pre-season soil tests for NO₃⁻-N, in-season plant tissue testing (petioles) for N fertility status, and crop monitoring to ascertain crop fruiting patterns and crop N needs. At each location, treatments varied from a conservative to a more aggressive approach of N management. Results at each location revealed a strong relationship between the crop fruit retention levels and N needs for the crop. This pattern was further reflected in final yield analysis as a response to the N fertilization regimes used. The higher, more aggressive N application regimes did not consistently benefit yields at any location. Generally, the more conservative, feedback approach to N management provided optimum yields at all locations. In 2001, a transition project evaluating the residual N effects associated with each treatment regime was initiated and no fertilizer N was applied. Therefore, all N taken-up by the crop was derived from residual soil N. In 2001, there were no significant differences among the original fertilizer N regimes in terms of residual soil NO₃⁻-N concentrations, crop growth, development, lint yield, or fiber properties. The lint yields were very uniform at each location and averaged 1500, 1100, and 850 lbs. lint/acre for MAC, MAR, and SAC, respectively. In 2002, results were very similar at the MAC and MAR locations. Trends associated with residual fertilizer N effects are not evident at either location just two seasons following N fertilizer applications.
    • Review of the 2002 Arizona Cotton Season

      Silvertooth, Jeffrey C. (College of Agriculture, University of Arizona (Tucson, AZ), 2003-05)
    • Short Staple Variety Trial in Cochise County, 2002

      Clark, L. J.; Norton, E. R. (College of Agriculture, University of Arizona (Tucson, AZ), 2003-05)
      Twelve varieties were tested including two New Mexico Acalas, two California Acalas from CPCSD, the new Arizona Cotton Grower’s variety and seven other upland varieties. Among the twelve varieties, eight contained the roundup resistant gene, which is very important for the high elevation trials. Four of these roundup resistant varieties were stacked gene varieties also containing the Bollgard trait. The highest yielding variety in the trial was 1517-99, with a yield approaching 800 pounds of lint per acre. This yield was lower than seen in 2001. In addition to the plant mapping data and HVI data which are provided, estimates of the crop values are also included in this report.
    • Short Staple Variety Trial in Virden, NM, 2002

      Clark, L. J.; Norton, E. R. (College of Agriculture, University of Arizona (Tucson, AZ), 2003-05)
      Twelve varieties were tested including two new herbicide resistant entries from California, Riata and Nova, two New Mexico Acalas, seven roundup resistant entries from Delta and Pine Land Co., Stoneville, SureGrow and FiberMax, and the new variety developed for the Arizona Cotton Grower’s Association, AG 3601. The highest yielding variety in the trial was FM 989 with a yield of 1045 pounds of lint per acre. It was also the highest yielding variety at this location last year. The Acala 1517-99 placed second in yield at 1039 pounds of lint per acre. HVI data are also included in this report.
    • Susceptibility of Arizona Pink Bollworm to Cry1Ac Following Six Years of Intensive Use of Transgenic Bt Cotton in Arizona

      Denney, Timothy J.; Shriver, Laura; Sims, Maria A.; Holley, Danny; Carrière, Yves; Tabashnik, Bruce; Antilla, Larry; Whitlow, Mike; Department of Entomology, The University of Arizona, Tucson, AZ; Arizona Cotton Research and Protection Council, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 2003-05)
      We summarize information on the performance of Bt cotton against pink bollworm (PBW), Pectinophora gossypiella, in Arizona following six years of use of this new technology. Monitoring of PBW susceptibility to Bt toxin Cry1Ac was conducted annually since 1997 by collecting insects from ten to 17 cotton fields, culturing strains in the laboratory, and measuring susceptibility to Cry1Ac in diet-incorporation bioassays. Based on survival in discriminating concentration bioassays of 10 μg Cry1Ac/ml of insect diet, resistant PBW were detected in low frequencies at 10 out of 17 Arizona locations sampled in 2001 and ranged from 0.0 to 4.0%. Though significantly more abundant than in the previous three seasons, resistant PBW were statistically less abundant in 2001 than they were in 1997. One collection from Paloma, AZ, had 4.0% survivors (uncorrected, actual survival) in bioassays of 10 μg/ml and samples from Coolidge, Maricopa, and Parker Arizona yielded • 1.0% survivors of this concentration. Susceptibility of a limited numbers of 2001 collections of PBW from California, New Mexico and Texas is also reported. Bioassays of 2002 collections are underway at the time of this writing. In a parallel effort, field efficacy of Bt cotton against PBW was documented at five to 39 Arizona locations per year since 1995 by collecting cotton bolls at seasons’ end and counting PBW and exit holes. In 39 pairs of adjacent Bt and non-Bt fields evaluated in 2001 by the Arizona Cotton Research and Protection Council, mean end-of-season pink bollworm infestation levels were > 15% for non-Bt fields and were < 0.15% in adjacent Bt fields. Thus, field observations indicated that performance of Bt cotton continued to be excellent throughout Arizona in the 2002 season.
    • Twin-Line Per Bed Plant Population and Variety Evaluation

      Husman, Stephen H.; McCloskey, Wililam B.; White, Kyrene (College of Agriculture, University of Arizona (Tucson, AZ), 2003-05)
      Two experiments were conducted at the University of Arizona Maricopa Agricultural Center in 2002 designed to evaluate cotton yield and fiber quality at various plant populations and to test cotton variety performance in a twinline per bed cotton production system. The plant population experiment consisted of four target populations which included 60, 80, 100, and 120,000 plants per acre (PPA) and two varieties, Stoneville 4892BR and AG3601. The resulting plant populations were 52800, 69200, 82800 and 96200 for ST4892BR and 54800, 70800, 90500 and 104500 for AG3601. The two lowest plant populations resulted in the highest lint yields for both varieties and were similar but there was a significant linear of decreasing yield with increasing plant population. The highest lint yields in the twin line variety experiment were DP449BR (1743 lb/acre) and DP5415R (1702 lb/acre) which were not statistically different.