• Effect of Plant Water Status on Defoliation of Pima Cotton

      Nelson, J. M.; Hart, G. L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      A study was conducted at the University of Arizona Maricopa Agricultural Center, Maricopa, AZ in 1994 to determine the influence of plant water status at the time of defoliation on effectiveness of defoliants and yield of Pima cotton. Several irrigation termination dates were used to achieve different levels of plant water stress at the time defoliants were applied. A single application of defoliants did not provide adequate defoliation under the conditions of this test. The earliest irrigation termination date resulted in the highest defoliation percentage. High CWSI values at the time defoliants were applied were related to the highest defoliation percentages, but were not necessarily related to satisfactory defoliation. The CWSI appears to have limited value as a guide to determine when to defoliate Pima cotton.
    • Effect of Planting Date on Yield of Upland and Pima Cotton Varieties at Marana

      Unruh, B. L.; Silvertooth, J. C.; Brown, P. W.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      A single field experiment was conducted at Marana Agricultural Center (2000 fl elevation) to evaluate the response of one Pima (G. barbadense L) and two Upland (Gossypium hirsutum L.) cotton varieties to three different planting dates. Planting dates ranged from 12 April to 16 May. In general there was decreasing lint yield with later planting dates.
    • Effect of Soil and Foliar Applied Potassium on Pima and Upland Cotton at Two Arizona Locations

      Galadima, A.; Silvertooth, J. C.; Unruh, B. L.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Due to increasing emphasis and interest being placed on cotton (Gossypium spp.) fiber quality as well as yield benefits associated with potassium (K) fertilization, two studies were conducted in 1994. These studies with those before them were aimed at assessing the agronomic necessity of K fertilization in Arizona cotton production. The locations of the trials included Maricopa Agricultural Center (Casa Grande sandy loam) and Safford Agricultural Center (Pima clay loam). At the Safford location, both Upland (G. hirsutum L., var. DPL 90) and Pima (G. barbadense L., var. S-7) cotton were planted with treatments that included both soil and foliar K applications. The trials at Maricopa Agricultural Center included four foliar K applications over the growing season on Pima (G barbadense L., var. S-7) cotton. The results of the experiments at both locations indicated no lint yield responses to K fertilization by either Upland or Pima cotton.
    • Establishment of a Whitefly Resistance Documentation and Management Program in Arizona

      Dennehy, T. J.; Simmons, A.; Russell, J.; Akey, D.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Adult whiteflies were collected from six regions of Arizona and evaluated for susceptibility to fenpropathrin (Danitol®), acephate (Orthene®) and endosulfan (Thiodan®), and mixtures of fenpropathrin+acephate curl fenpropathrin+endosulfan. Strong indications of resistance to fenpropathrin, acephate and the fenpropathrin +acephate mixture were documented in some areas of the state. With all populations evaluated endosulfan was consistently the most toxic of the insecticides evaluated (singly) and was highly toxic in mixtures with fenpropathrin. Whitefly resistance to pyrethroid insecticides and especially mixtures of pyrethroid+organophosphate insecticides could have serious ramifications for the prevention of sticky cotton in Arizona. To combat further development of pyrethroid resistance cotton growers will need to reduce the number of pyrethroid treatments made per season.
    • Evaluation of a Feedback Approach to Nitrogen and Pix Application

      Silvertooth, J. C.; Norton, E. R.; Unruh, B. L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      A single field experiment was conducted in 1994 at Maricopa, AZ to compare a scheduled approach (based on stage of growth) versus a feedback approach (based on vegetative status) to both nitrogen (N) and mepiquat chloride (PIX™) applications on Upland cotton (Gossypium hirsutum L.). PIX feedback treatments were based upon fruit retention (FR) levels and height: node ratios (HNRs) according to established baselines. Scheduled PIX applications were made for a total of 1.0 pt./acre over two applications, with feedback PIX treatments receiving a single 0.5 pt./acre application near peak bloom (approx. 2200 heat units after planting (HUAP), 86/55 °F threshold) Scheduled applications of fertilizer N totaled 225 lbs. N/acre from four applications and feedback N treatments received a total of 135 lbs. N/acre from three 45 lb. N/acre applications. Treatments consisted of all combinations of scheduled or feedback applications of both N and PIX. The highest lint yields were from a treatment receiving feedback N and PIX and a treatment receiving scheduled N and PIX, which were not significantly differencent (P ≤ 0.05) from one another. From a practical standpoint, however, these treatments were very different in terms of the magnitude in differences of fertilizer N and PIX required to produce comparable yields.
    • Evaluation of a Leaf-turn Method for Sampling Whiteflies in Cotton

      Diehl, J. W.; Ellsworth, P. C.; Naranjo, S. E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Plans for sampling sweetpotato whiteflies in cotton were evaluated within 8,000 acres of cotton within central Arizona. These plans were found to be a practical and efficient way to track whitefly populations. In general they should add about 8 minutes to a pest sampling regime. Neither time of day nor sampler experience were found to have a significant effect on the number of whiteflies counted. Therefore, this method provides a common currency for growers, PCAs and others to compare whitefly numbers among fields and through time.
    • Evaluation of Late Season Pix™ Applications

      Norton, E. R.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      The effects of late -season Palm on the growth characteristics and yield of Upland cotton was examined in this study. Three treatments were imposed late-season (3447 HUAP), 1, a check plot, receiving no Pix™, 2 receiving 0.75 pt/acre, and 3; receiving 1 pt/acre. The imposed treatments did not have a statistically significant effect on plant growth characteristics or earliness nor were there any significant overall yield differences detected among treatments.
    • Evaluation of Soil Conditioners and Water Treatments for Cotton Production Systems

      Unruh, B. L.; Silvertooth, J. C.; Sanchez, C. A.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Advanced technologies to produce synthetic polymers such as polyacrylamide (PAS, and polymaleic anhydride (PMA) have produced products which may be economically feasible alternatives to traditional treatments such as gypsum in the desert Southwest. In 1994 three field studies were initiated, two identical studies were located in the Yuma Valley and one at Paloma Ranch. At Yuma Valley the experiments included 0, 1, and 2 tons gypsum/acre, over which, various soil-applied treatments were made; including, a check, soluble PMA (Sper Sal™), and PAM (Hydro-Growth™). Upland cotton 'DPL 5461' was grown in both Yuma Valley studies. At Paloma Ranch, Upland 'DPL 5415' planted. Prior to planting, two gypsum applications were made at 0 and 2 tons/acre. Also included as treatments were various methods and rates of Sper Salt™. No differences among treatments were detected in either of these locations relative to crop yield. At Paloma Ranch there were some early-season differences in soil crusting among the various soil amendment treatments, however, these differences dissipated as the season progressed and did not result in lint yield differences.
    • Host Preference of Silverleaf Whitefly and Factors Associated with Feeding Site Preference

      Chu, C. C.; Hennberry, T. J.; Cohen, A. C.; Silvertooth, Jeff; USDA-ARS, Western Cotton Research Laboratory, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Silverleaf whitefly (SLW), Bemisia argentifolii, Bellows and Perring, preferred cantaloupe to cotton, broccoli and lettuce in field and greenhouse studies. In the absence of cantaloupe, SLW preferred cotton to broccoli and lettuce. In the field, more eggs and fewer nymphs were found on broccoli than on cotton. Differences in the relative abundance of vascular bundles per unit of leaf area between the four plant species may partly account for differences in oviposition site selection. Vascular bundle volume/unit of leaf tissue volume was 50% greater in cantaloupe than in cotton and broccoli, which in turn were significantly greater than in lettuce. Most SLW on cotton leaves are found on underside leaf surfaces. Distances from top and underside leaf surfaces to the nearest vascular bundles in cotton leaves were 131 and 60 tun, respectively, in the present studies.
    • 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).
    • Irrigation Efficiencies and Lint Yields of Upland Cotton Grown at the Maricopa Agricultural Center, 1994

      Sheedy, Mike; Watson, Jack; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      A field trial was conducted at the Maricopa Agricultural Center to observe the effects of four irrigation efficiencies (65 %, 75 %, 85 %, and 95 %) on the lint yield produced from two upland cotton varieties (DP 5415 and DP 5816). Nitrogen requirements for the crop were determined using pre -season soil samples and in-season petiole samples with data collected from crop monitoring at weekly intervals. AZSCHED was used as a guide to the irrigation timing and amount of water applied during the season. The irrigation efficiency did not have an effect on the lint yield of the cotton crop regardless of variety, but there was a significant difference in yield between the varieties. Lint yields ranged from 1165 #/acre to 1299 #/acre for DP 5415 and 869 #/acre to 986 #/acre for DP 5816.
    • Irrigation Frequency and Cotton Yield in Short-Season Cotton Systems

      Chu, Chang-chi; Henneberry, Thomas J.; Silvertooth, Jeff; USDA-ARS, Western Cotton Research Laboratory, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      We tested the hypothesis that small frequent irrigations during the July cotton peak fruiting stage would result in better fruiting and higher cotton yields than the same amount of water applied less frequently. Over three years under a short - season production system, irrigation intervals of every 5-d with 42 mm of water applied at each irrigation increased cotton lint yield by 5-11 % compared to irrigation intervals of 10- and 15-d with 80 and 130 mm of water applied at each irrigation, respectively. The results show that small, frequent furrow irrigations during cotton fruiting are highly effective in reducing water deficit during critical growth stages and improved lint production in a short - season cultural system. Soil salt content in the top 15 cm of soil was not increased after three years of study.
    • Multiple Plant Growth Regulator Use on Short Staple Cotton

      Hood, L. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      A field trial was conducted during the 1992 & 1993 growing seasons to evaluate the activity of Cytokin and Pic applied alone or in combination to short staple cotton. The Cytokin treatment significantly increased tint yield over the other treatments in 1992. There were no statistically significant seed cotton differences between the non - treated check and any treatment in 1993. Fruit retention remained high throughout 1992 and very high throughout the 1993 season. Under high fruiting conditions, use of a plant growth regulator would not normally be recommended.
    • Nitrogen Management BMPs Parker Valley Demonstration

      Watson, J.; Winans, S.; Sheedy, M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      A nitrogen management demonstration was conducted in the Parker Valley in 1994. Grower nitrogen application practices were compared with nitrogen application recommendations based upon pre plant soil samples plus petiole nitrates and plant mapping data. The only significant difference in amounts applied occurred in May, with grower applied rates exceeding recommended rates. Grower rationale for the application was logical, however, it being dependent upon the uncertainty of irrigation timing in June.
    • Nitrogen Management Experiments for Upland and Pima Cotton, 1994

      Silvertooth, J. C.; Norton, E. R.; Unruh, B. L.; Navarro, J. A.; Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Three field experiments were conducted in Arizona in 1994 at three locations ( Maricopa, Marana, and Safford). The Maricopa and Safford experiments have been conducted for six consecutive seasons, with consistent plot locations; the Marana site was initiated in 1994. The purposes of the experiments were to validate and refine nitrogen (N) fertilization recommendations for both Upland and Pima cotton. The experiments 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. 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 effects of N fertility levels have been consistently evident in crop maturity and its relationship to lint yields.
    • Pima Cotton Genetics

      Percy, R. G.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      A short season feasibility study, using early maturing Pinta genotypes was conducted for a second season. Four early maturing genotypes, a short season check (P62) and a full season check variety (PS-7) were evaluated in replicated tests under short season and full season regimes. In both 1993 and 1994, most genotypes reached cutout around August 4, with 2759 accumulated heat units. All genotypes were earlier maturing than PS-7, as indicated by plant growth measurements and by sequential harvests. In 1994, the four early maturing experimental genotypes produced yields equal to or slightly better than the longer season cultivar PS-7. No differences in yield occurred between the short season and standard practice management systems in either year. A fiber improvement project was initiated in 1989 with the primary goals of increasing the fiber length and strength potential of Pima cotton. In 1989 the early maturing, short statured Pima strain P62 was crossed to Giza 45 and Giza 70 to transfer the fiber strength of those varieties into a heat tolerant, earlier maturing, productive Pima background. Likewise, P62 was crossed to the Sea Island cultivar St. Vincent V-135 with the objective of transferring the latter cultivar's long fiber length into an agronomic Pima background. Two resulting lines, one possessing high fiber strength and the other possessing high fiber length are planned for release in 1995-96.
    • Pima Cotton Improvement

      Moser, H. S.; Percy, R. G.; Ray, I. M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      The objective of this study was to evaluate the performance of five experimental lines (P73, P75, P76, P80, and P81) with two commercial varieties ('Pima S-6' and 'Pima S-79 of Pima cotton. All seven strains were grown in replicated strip tests at four locations across the Pima belt in 1994. While none of the experimental lines produced significantly more lint than the best Pima variety at any site, some of them possess traits that are valuable to Pima cotton breeders. P73 has long and strong fiber. P76 is a high yielding, early maturing line that produces long and strong fiber. P80's lint yields are similar to Pima S-7, but it is significantly earlier.
    • Pima Cotton Regional Variety Trial, Safford Agricultural Center, 1994

      Clark, L. J.; Carpenter, E. W.; Hart, G. L.; Nelson, J. M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Ten long staple varieties (including two Pima experimental lines) were tested in a replicated small plot trial on the Safford Agricultural Center in Graham county at an elevation of 2950 feet. Even though the total number of heat units received during the season was nearly as high as the previous year, the average yield was nearly 300 pounds per acre lower. Olvey and Associates OA 304 was the highest yielding variety with a yield of 776 pounds per acre of lint and only two varieties broke the bale and a half mark. Yield and other agronomic data as well as fiber quality data are contained in this paper.
    • Pima Regional Variety Test; Maricopa Agricultural Center, 1994

      Hart, G. L.; Nelson, J. M.; Clark, L. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Nine Pima varieties and experimental strains were grown in a replicated trial at the Maricopa Agricultural Center. Lint yield, boll size, lint percent, plant population and fiber property data are presented in this report.
    • Plant Growth Regulator Studies at the Safford Agricultural Center, 1994

      Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Methanol, Cytokin and PGR IV plant growth regulators were tested on long and short staple cotton on the Safford Agricultural Center in 1994. It was a follow up study on Methanol and Cytokin and a first time look at PGR IV.