• Residual Soil Nitrogen Evaluations in Irrigated Desert Soils, 2004

      Silvertooth, J. C.; Galadima, A.; Norton, E. R.; Tronstad, Russell; Husman, Steve; Norton, Randy (College of Agriculture, University of Arizona (Tucson, AZ), 2005-05)
      Field experiments aimed at investigating N fertilizer management in irrigated cotton production have been conducted for the past 16 seasons at three Arizona locations on University of Arizona Agricultural Centers (Maricopa, MAC; Marana, MAR; and Safford, SAC). In 2004, 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 reveal 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 increase 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, 2002, 2003 and even 2004 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 in 1991 and averaged 1500, 1100, and 850 lbs. lint/acre for MAC, MAR, and SAC, respectively. In 2002, results were very similar and yields averaged at 1473 and 1060 lbs. lint/acre for MAC and MAR locations respectively. The 2003 results were not different from the prior two years of results and yields averaged at 1322 and 1237 lbs. lint/acre for MAC and MAR respectively. In 2004, yields averaged 828 and 1075 lbs. lint/acre. Trends associated with residual fertilizer N effects are not evident at either location four seasons following N fertilizer applications.
    • Review of the 2004 Arizona Cotton Season

      Tronstad, Russell; Husman, Steve; Norton, Randy; Norton, Eric; Clay, Pat; Zerkoune, Mohammed; Tronstad, Russell; Husman, Steve; Norton, Randy (College of Agriculture, University of Arizona (Tucson, AZ), 2005-05)
    • Scheduling Techniques for the Use of Pentia Plant Growth Regulator

      Norton, E. R.; Tronstad, Russell; Husman, Steve; Norton, Randy (College of Agriculture, University of Arizona (Tucson, AZ), 2005-05)
      A single field study was conducted at the University of Arizona Safford Agricultural Center during the 2004 season to evaluate the utilization of a feedback technique that is based upon plant growth and development to schedule applications of the new plant growth regulator (PGR) from BASF, Pentia. A simple three treatment study was constructed consisting of a control treatment (no Pentia application), a scheduled treatment (application of 16 oz/acre at first bloom regardless of plant growth), and a feedback treatment (applications based upon plant growth and development). Application decisions on the feedback treatment were made using height to node ratios (HNR) as a measure of plant vigor. Treatment applications were made on the scheduled regime on 14 July with a one time 16 oz/acre application. The feedback regime received an application (16 oz/acre) of Pentia five days later on 19 July. An additional application (16 oz/acre) was made on the feedback treatment on 3 August due to continued high HNR levels. Significant differences in plant vigor were observed post application among the three treatments as measured by end of season HNR ratios. Yield results indicated positive lint yield response to Pentia application with both the scheduled and feedback treatment producing statistically higher yields than the control. Differences between the feedback and scheduled treatments were not statistically different however a slight yield increase was observed in the scheduled treatment. The second Pentia application made to the feedback treatment was not necessary. End of season HNR measurements indicate that the additional 16 oz/acre application suppressed growth to below the average baseline for HNR. These results indicate that potential positive response to PGR applications, specifically Pentia, under conditions of high vigor.
    • Transitioning Lygus Chemical Controls to More Selective Options for Arizona Cotton

      Ellsworth, Peter C.; Barkley, Virginia; Tronstad, Russell; Husman, Steve; Norton, Randy; Department of Entomology & Arizona Pest Management Center, Maricopa Agricultural Center (College of Agriculture, University of Arizona (Tucson, AZ), 2005-05)
      Lygus hesperus (Knight) has been the number one pest of Arizona cotton since 1998. With advances in the selective management of Arizona cotton’s other two key pests (i.e., Bemisia tabaci and Pectinophora gossypiella), there has been less opportunity for collateral control of this yield-limiting pest. There has also been a new premium placed on locating less disruptive, even selective, control methods that are compatible with existing selective technologies. Our laboratory routinely screens candidate compounds for efficacy against Lygus hesperus under desert conditions. Promising leads are further developed and evaluated in the field for efficacy, spectrum of activity and safety for beneficial arthropods. Our recent findings have identified three compounds with potential for delivering economic control of Lygus hesperus with greater safety for beneficial arthropods than current standards of control. At the same time, our work has importantly identified many compounds that are ineffective against our Lygus, despite reported success against a related species, the tarnished plant bug, Lygus lineolaris (e.g., acetamiprid, imidacloprid, indoxacarb, pyrethroids, thiamethoxam). Flonicamid, a pyridine carboxamide, is under development by FMC in the U.S. This aphicide has shown excellent results in controlling our Lygus in cotton. Novaluron, a chitin inhibitor under development by Uniroyal (as Diamond®) in the U.S., has rate sensitive activity against Lygus in cotton. Metaflumizone (BAS320I), under development by BASF in the U.S., is a semi-carbazone chemistry with significant efficacy against Lygus hesperus. These three or potentially other new leads in insecticide discovery may play an important role in transitioning Arizona cotton growers away from neuro-toxic, broad-spectrum, and disruptive organophosphates and carbamates currently used to control Lygus in cotton. The potential benefits to natural enemy conservation should help stabilize insect pest management in Arizona cotton, thus minimizing the chances of secondary pest outbreaks and costly pest resurgences. Until selective alternatives are found and registered, acephate (e.g., Orthene 97 by Valent USA) and oxamyl (Vydate C-LV by DuPont) remain our standard recommendations for Lygus control in Arizona cotton.
    • Twin Line Cotton Production in a Conservation Tillage System

      Husman, S.; Clay, P.; Taylor, E.; White, K.; Tronstad, Russell; Husman, Steve; Norton, Randy; University of Arizona Cooperative Extension (College of Agriculture, University of Arizona (Tucson, AZ), 2005-05)
      Two experiments were conducted in 2004 evaluating twin line cotton production using a conservation tillage system approach. DPL 451 BR Upland cotton was planted into oat hay stubble on April 30 and May 5, 2004 at commercial cooperator sites at Tonopah and Tolleson AZ, respectively. The two primary experimental objectives were to determine whether cotton planted into previous crop residue initiated fruiting on the mainstem once the cotton seedling grew above the crop stubble and whether there were differences in lint yield between the single and twin line system. Previous twin line cotton production research had been conducted by authors at 30 locations from 2001-2003. In almost all cases, the harvest of low set bolls presented problems with the twin line system. In 2004, the initiation of the first fruiting branch was independent of the stubble height at both locations. In addition, there were no differences in lint yield in either a single or twin line cotton production system when planting into previous crop residue using conservation tillage.
    • Upland Variety Testing Evaluation in Southeastern Arizona

      Norton, E. R.; Clark, L. J.; Borrego, H.; Tronstad, Russell; Husman, Steve; Norton, Randy (College of Agriculture, University of Arizona (Tucson, AZ), 2005-05)
      Two separate variety evaluations were conducted in southeastern Arizona during the 2004 cotton growing season. The two locations were on grower-cooperator fields in the Upper Gila River Valley located in Thatcher, AZ (Graham County) and in the Sulfur Springs Valley in Kansas Settlement, AZ (Cochise County). Twelve varieties were selected for the Graham County evaluation and fifteen in the Cochise County evaluation. These varieties included several transgenic varieties and ranged in maturity from early to full-season varieties. Several Acala varieties were also evaluated in both the Graham and Cochise County tests. Both evaluations were conducted using a randomized complete block design with each variety replicated four times. Plant measurements were collected in season on several dates from the Graham County evaluation. End of season plant measurements were collected from the Cochise County evaluation. Lint yield was estimated at each location by harvesting the entire plot and weighing the harvested seed cotton with a weigh wagon equipped with load cells. Sub samples were collected from each plot for fiber quality and percent lint determinations. Total crop value for each variety was calculated by using the fiber quality premium/discount and using a $0.52 per pound price. The total price is then multiplied by total lint yield to obtain the total value for that particular variety. Results observed in the Graham County evaluation were similar to those in 2003. Lint yield ranged from 1200 to over 1600 lbs. lint/acre. The FiberMax variety FM991BR produced the highest lint yield and also the highest total crop value at over $950/acre. Results from the Cochise County evaluation demonstrated the potential that high fiber quality can have on total crop value. Lint yields ranged from 600 to over 1200 lbs. lint/acre. The highest yielding variety (ST5242BR) did not produce the highest crop value. Because of the higher fiber quality of the Acala varieties, they produced the highest value at approximately $630/acre.
    • Weed Management and Agronomic Performance of a Cotton-Barely Double Crop Rotation

      Adu-Tutu, K. O.; McCloskey, W. B.; Husman, S. H.; Clay, P.; Ottman, M. J.; Martin, E. C.; Teegerstrom, T.; Tronstad, Russell; Husman, Steve; Norton, Randy (College of Agriculture, University of Arizona (Tucson, AZ), 2005-05)
      The tillage operations required to grow an annual barley and cotton crop rotation were reduced by eliminating tillage prior to planting cotton, eliminating cultivations for weed control in cotton, and especially by eliminating tillage following cotton. A light activated, weed sensing automatic spot-spray system reduced the amount of spray volume and herbicide used by 40% to 60% at Marana and 36% to 56% at Maricopa in 2004. At Maricopa, a large number of volunteer cotton plants in the furrows of early planted no-till cotton reduced the spray volume savings from using the weed sensing automatic spot-spray system. Weed control was similar with the weed sensing, automatic spot-spray system compared to the conventional continuous spray system for most weed species but weeds with narrow leaf, upright leaf canopies such as sprangletop, barley and skeleton weed were more difficult to detect and control. In both Marana and Maricopa, there were yield differences between treatments related to planting date, with late-planted cotton yielding less than early-planted cotton. At Marana, the early-planted conventional tillage cotton out-yielded the barley cover crop, early-planted no-till cotton treatment. At Maricopa, there were no yield differences between the two early planted cotton treatments; however, the late-planted conventionally tilled cotton yielded 28% more than the late-planted no-till cotton. Although the yield comparisons are not yet definitive, it appears that in some situations no-till cotton may yield less than conventionally tilled cotton. At Maricopa, the height of cereal crop stubble did not affect subsequent cotton establishment, field populations, plant height or lint production (2003 and 2004) and the position or node of the first fruiting branch and the first retained boll were similarly unaffected in 2004.