• N Volatilization from Arizona Irrigated Waters

      Norton, E. R.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      A laboratory study was initiated to investigate the potential loss of fertilizer nitrogen (N) through volatilization at four different temperatures (25, 30, 35, and 40°C) out of irrigation waters collected from a number of Arizona locations. Complete water analysis was conducted on each of the water samples. A 300 ml volume of each water was placed in 450 ml beakers open to the atmosphere in a constant temperature water bath with 10 mg of analytical grade (NH₄)₂SO₄ added to each sample. Small aliquots were drawn at specific time intervals over a 24 hour period and then analyzed for NH₄⁺-N concentrations. Results showed potential losses from volatilization to be highly temperature dependent. Total losses (after 24 hours) ranged from 30-48% at 25°C to over 90% at 40°C. In this study where (NH₄)₂SO₄ was used as the N source, the initial concentration of SO₄⁻-S in the solution had a repressive effect on volatilization due to the decreased availability of free NH₄⁺ in waters with high initial SO₄⁻-S concentrations due to the formation of complex ion pairs (NH₄SO₄⁻). It was also observed that at lower temperatures complexation and ion pair formation affected volatilization of NH₃ by reducing the NH₄⁺ activity in solution and thereby reducing NH₃ volatilization. Potential volatilization loss of fertilizer N from these irrigation waters was found to be significant and should be considered when making decisions regarding fertilizer N applications for crop production in Arizona.
    • Soil and Plant Recovery of Labeled Fertilizer Nitrogen in Irrigated Cotton

      Silvertooth, J. C.; Navarro, J. C.; Norton, E. R.; Galadima, A.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Proper timing of fertilizer N applications in relation to crop uptake can serve to improve fertilizer efficiency in irrigated cotton. Earlier research has identified an optimum application window extending from the formation of first pinhead squares to peak bloom, which corresponds well with maximum crop uptake and utilization. Field experiments were conducted at the University of Arizona Marana Agricultural Center (Grabe clay loam soil) utilizing sidedress applications of ammonium sulfate with 5-atom % 15-N at pinhead square, early bloom, and peak bloom at a rate of 56 kg N/ha. The objective was to compare relative efficiencies in terms of fertilizer N uptake and recovery among these three times of application. Results indicate that all treatments averaged approximately 80% total fertilizer N recovery. Of the fertilizer N that was recovered, approximately 40 % was taken up by the plants and 60 % recovered in the soil, primarily in the top 60 cm of the soil profile.
    • Summary of Nitrogen Management Experiments in Irrigated Cotton

      Silvertooth, J. C.; Norton, E. J.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      A series of nitrogen management experiments have been conducted over the past 11 years around the state to develop and refine fertilizer nitrogen (N) recommendations for irrigated desert cotton production. Stability analysis was used to summarize the data and to determine which of the four treatment regimes is most stable over a range of environments. Results indicate that the feedback treatment (treatment 3) was the most stable treatment for both Upland and Pima cottons and provided the best probability for a higher yield under high yielding environments. The untreated control treatment (treatment 1) was the least stable over a wide range of environments. These results further validate the ‘feedback’ approach to management of fertilizer N.
    • Nitrogen Management Experiments For Upland and Pima Cotton, 2000

      Silvertooth, J. C.; Norton, E. R.; Galadima, A.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Two field experiments were conducted in Arizona in 2000 at two locations (Maricopa and Marana). The Maricopa experiment has been conducted for nine consecutive seasons; the Marana site was initiated in 1994. The purposes of the experiments were to validate and refine nitrogen (N) fertilization recommendations for Upland 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. 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 benefit yields at any location. In 2000, fruit retention levels were good and crop vigor was not excessive. The more conservative, feedback approach to N management provided optimum yields at both locations.
    • Evaluation of a Drip Vs. Furrow Irrigated Cotton Production System

      Norton, E. R.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      A newly installed subsurface drip system was compared to a conventional furrow-irrigated cotton production system in the Marana Valley in 2000. Regular measurements included soil moisture, flower tagging, general plant growth and development measurements, and lint yield. Results indicate that an increase in lint yield of approximately 250 lbs. lint/acre was obtained under the drip irrigation system. Approximately 1/3 less irrigation water was used under the drip irrigation system. Pounds of lint produced per acre-inch of water applied provide the most dramatic results. In the furrow-irrigated system approximately 25 lbs. of lint was produced per inch of water applied while the drip system ranged from 70-80.
    • Effects of High Frequency Irrigation on Irrigation Uniformity III

      Martin, E. C.; Laine, G.; Sheedy, M.; Silvertooth, Jeff; University of Arizona, Cooperative Extension (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Data was collected for a third season to determine the effects of high frequency irrigation on irrigation uniformity in cotton production. The past two seasons indicated that high frequency irrigation worked better on sandier soils than soils containing high clay contents. Although no significant differences were found, higher yields were obtained on a site with a relatively high sand content. A field located at the Maricopa Agricultural Center was split into two treatments. Treatment 1 was irrigated at approximately 35% depletion of available water in the plant rootzone. Treatment 2 was irrigated at approximately 50% depletion in the crop rootzone. Although the yield data from Treatment 1 was higher on the average, statistically, there was no difference between the two treatments.
    • Pima Cotton Regional Variety Trial, Safford Agricultural Center, 2000

      Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Twenty five long staple varieties were tested in a replicated small plot trial on the Safford Agricultural Center in Graham county at an elevation of 2950 feet. The highest yielding variety in this study was Hazera 83-208 with a yield of 1180 pounds of lint p1er acre. This interspecific hybrid from Israel was the highest yielding cultivar in the 1999 test, also. The top five varieties consisted of two interspecific hybrids from Isreal, a variety developed by the University of Arizona and entries from Buttonwillow Research and California Planting Cotton Seed Distributors (CPCSD). The average yield in the trial was the same as last year, but the highest yield was slightly lower. Yield and other agronomic data as well as fiber quality data are contained in this paper.
    • Short Staple Variety Trial in Virden, NM, 2000

      Clark, L. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Twelve varieties were tested including three New Mexico Acalas and one Acala from Buttonwillow Research in California, three roundup ready varieties, a buctril resistant variety, a Bollgard variety and three other varieties. The highest yielding variety in the trial was FM 989 with a yield of 1046 pounds of lint per acre. It was also the highest yielding variety in the Cochise County trial the past two years, but had not been grown in Hidalgo or Greenlee Counties before. BW 9802, a variety from Buttonwillow Research in California, came in a close second. Interesting HVI data are also included in this report.
    • Acala Cotton Variety Trial, Safford Agricultural Center, 2000

      Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Eighteen Acala cotton varieties were tested in a replicated small plot trial on the Safford Agricultural Center in Graham county at an elevation of 2950 feet. The highest yielding variety in this study was Hazera 195-208, an interspecific hybrid from Israel, with a yield of 1387 pounds of lint per acre. It was followed closely by two varieties from New Mexico, 1517-99 and B7514. Hazera 195-208 had the highest yield in an interspecific hybrid study and 1517-99 was the highest yielding Acala variety in the Upland cotton regional variety trial in 1999 (1). The next five varieties consisted of two interspecific hybrids from Israel, a variety from Buttonwillow Research and two advanced strains from New Mexico. Yield and other agronomic data as well as fiber quality data are contained in this paper.
    • Short Staple Variety Trials in Cochise County, 2000

      Clark, L. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Twelve varieties were tested including three New Mexico Acalas and one Acala from Buttonwillow Research in California, three roundup Ready varieties, a buctril resistant variety, a Bollgard variety and three other varieties. The highest yielding variety in the trial was 1517-99, with FiberMax 989, 1517-95 and SureGrow 521RR following in yield. Yields were considerably lower than seen in the previous year’s study (1). Several Roundup Ready varieties were included in this study. Plant mapping data and HVI data are also included in this report.
    • Short Staple Variety Trials, Graham County, 2000

      Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      One replicated on-farm short staple variety trial was planted in Graham County in 2000. Ten varieties were evaluated on the Larson farm in Thatcher. Several new varieties were planted in these studies, including 5 transgenic varieties, 3 varieties from Buttonwillow Research in California, and the newest acala from New Mexico. The Australian variety, FiberMax 989, produced the highest yield with 895 pounds of lint per acre. Paymaster 1560 BRR and DPL 655BRR followed close behind and were not separable statistically from the leader. Yield and other agronomic data are reported by variety along with HVI values from the lint.
    • Upland Cotton Regional Variety Trial, 2000

      Hart, G.; Moser, H.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Each year the University of Arizona conducts upland cotton variety tests to evaluate the performance of a diverse set of experimental and commercial varieties in Arizona. One such program is the Regional Variety Test (RVT). In 2000, we evaluated a total of 61 varieties at one or more locations in Arizona. These varieties were submitted to us for testing by 13 private seed companies and three public breeding programs. This report presents the results of the trials conducted at Maricopa, Marana, Safford and Yuma.
    • Arizona Upland Cotton Variety Testing Program, 2000

      Moser, H.; Hart, G.; Clark, L.; Husman, S.; Clay, P.; Zerkoune, M.; Guerena, M.; Silvertooth, J.; Silvertooth, Jeff; University of Arizona Cooperative Extension (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Each year the University of Arizona conducts variety trials across the state to evaluate the performance of upland cotton varieties. These tests provide unbiased data on the performance of varieties when tested side-by-side under typical production practices. In 2000, we planted a total of ten trials, one in the southwestern region (Yuma county), six in the central region (MoHave, La Paz, Maricopa, and Pinal counties), one in the southern region (Pima county), and two in the eastern region (Graham and Cochise counties). We tested six to ten commercially available varieties in each test. The purpose of this report is to present the results of our 2000 tests conducted in southwestern, central and southern Arizona. Lee Clark presents results from eastern Arizona in two companion reports in this publication. The results show that many varieties performed well at several locations, indicating good adaptation to Arizona conditions. The highest yielding varieties did not always produce the most value per acre, clearly demonstrating the importance of both yield and fiber quality in determining the value of the crop. Growers should carefully weigh the costs and benefits of yield, quality, and transgenic technology when selecting varieties.
    • 2000 Low Desert Upland Cotton Advanced Strains Testing Program

      Husman, S.; Moser, H.; Wegener, R.; Silvertooth, Jeff; University of Arizona Cooperative Extension (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Upland cotton advanced strains and commercial check comparison varieties were evaluated in replicated field studies at four locations in 2000. The test sites include Yuma, AZ., Buckeye, AZ., Maricopa, AZ., and Safford, AZ.. Nine seed companies submitted a maximum of five advanced strains entries per location. Three commercial check varieties were used at each site for comparison purposes and included DP 5415, SG 125, and STV 474.
    • Heat Stress and Cotton Yields in Arizona

      Brown, Paul W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Yield of upland cotton was related to heat stress in Yuma, LaPaz, Maricopa, and Pinal Counties for the period 1987-1999. Heat stress during the primary fruiting cycle was assessed using heat stress units (HSU) which were derived from mean daily canopy temperatures computed using a canopy temperature model and local AZMET weather data. Mean lint yields were computed for years with low, intermediate and high levels of HSU. Yields in years with low levels of heat stress were always significantly greater than yields in years with high levels of heat stress. Differences in yield between high and low heat stress years ranged from 100 lb/a in Maricopa County to 254 lb/a in Yuma County and averaged 166 lb/a across all counties. Differences in yield between the low and intermediate stress years, and intermediate and high stress years averaged 86 and 80 lb/a, respectively across all counties; however, these differences were not always significant in individual counties.
    • Recent Yield and Fiber Micronaire Tendencies for Upland Cotton in Arizona

      Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Problems associated with increasing trends towards high micronaire values for Upland cotton (Gossypium hirsutum L.) have been a matter of concern for the Arizona cotton industry in recent years. The discounts on fiber value associated with high micronaire has been compounded by the fact that market prices for cotton fiber has been very low in recent years and yields have been stable at best. An evaluation of recent yield and fiber quality data from a number of locations in Arizona was evaluated in relation to trends within Arizona and across the U.S. cotton belt. Results indicate similar patterns exist in terms of stable yields (yield plateau) and increasing micronaire values between Arizona and other U.S. cotton producing states. The conclusion is presented that these patterns are at least due in part to a common genetic base for varieties that grown in Arizona and beltwide. There also appears to be some distinct relationships associated with high micronaire with region and individual farm management practices.
    • Defoliation of Pima and Upland Cotton at the Safford Agricultural Center, 2000

      Clark, L. J.; Coleman, R. D.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Nine defoliation treatments based on defoliating agents that are in use in the area plus two additives (compounds A, B) were applied to Pima and Upland cotton to compare the treatment effects on percent leaf drop and yields. All of the treatments were beneficial to leaf drop compared to the untreated check with the Ginstar treatments generally performing better than the chlorate. One of the additives enhanced the early defoliation effectiveness of chlorate, the other additive enhanced the effectiveness of Ginstar throughout the defoliation process. More studies will be needed before recommendations can be made.
    • Evaluation of Crop Management Effects on Fiber Micronaire, 2000

      Silvertooth, J. C.; Galadima, A.; Norton, E. R.; Tronstad, R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Arizona has experienced a trend toward increasing fiber micronaire values in recent years resulting in substantial discounts on fiber value. There is some evidence to suggest management can impact fiber micronaire. Approximately 250 cases were identified in cotton production areas in Arizona ranging from the lower Colorado River Valley to near 2,000 ft. elevation with grower cooperators in the 2000 season. Field records were developed for each field by use of the University of Arizona Cotton Monitoring System (UA-CMS) for points such as variety, planting date, fertility management, irrigation schedules, irrigation termination, defoliation, etc. Routine plant measurements were conducted to monitor crop growth and development and to identify fruiting patterns and retention through the season. As the crop has approached cutout and the lower bolls began to open, open boll samples have been collected from the lowest four, first position bolls (theoretically the bolls with the highest micronaire potential on the plant) from 10 plants, ginned, and the fiber analyzed for micronaire (low 4). From that point forward, total boll counts per unit area and percent open boll measurements are being made on 14-day intervals until the crop is defoliated. Following defoliation, final plant maps were performed. Relationships among low 4 samples micronaire, irrigation termination (IT), defoliation, and final crop micronaire were analyzed.
    • Evaluation of Irrigation Termination Effects on Fiber Micronaire and Yield of Upland Cotton, 2000

      Silvertooth, J. C.; Galadima, A.; Norton, E. R.; Moser, H.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Arizona has experienced a trend toward increasing fiber micronaire values in recent years resulting in substantial discounts on fiber value. There is some evidence to suggest that irrigation termination management can impact fiber micronaire. A single field study was conducted in 2000 at the Maricopa Agricultural Center (1,175ft. elevation) to evaluate the effects of three dates of irrigation termination on the yield of 13 Upland cotton varieties. Planting date was 6 April (668 HU/Jan 1 86/55° F thresholds). Three dates of irrigation termination (IT1, IT2, and IT3) were imposed based upon crop development into cutout. The earliest irrigation termination date, IT1 (24 July) was made slightly ahead of an optimum date to provide sufficient soil-water such that bolls set at the end of the first fruiting cycle would not be water stressed and could be fully matured. Thus, the IT1 date was imposed to try to reduce overall micronaire. The second termination (IT2) date was 17 August, and provided one additional irrigation over an optimal point for the first cycle fruit set and two irrigations beyond IT1. The final (IT3) date was 15 September, which was staged so that soil moisture would be sufficient for the development of bolls set up through the last week of September thus providing full top-crop potential. Lint yield and micronaire results revealed significant differences among the IT treatments. Micronaire and lint yield values increased with later IT dates.
    • Planting Date Effects Crop Growth and Yield of Several Varieties of Cotton, Marana 2000

      Silvertooth, J. C.; Galadima, A.; Norton, E. R.; Moser, H.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      A field study was conducted in 2000 at the University of Arizona Marana Agricultural Center (1,974 ft. elevation) to evaluate the effects of three planting dates on yield and crop development of 13 varieties of upland cotton. Planting dates included 4 April, 21 April, and 9 May. The associated heat units accumulated since 1 January were 617, 877, and 1203 respectively (using 86/55 °F maximum/minimum thresholds respectively). Results indicate that there was a significant interaction between planting date and variety. Overall, lint yields significantly declined with later planting dates and significantly varied among varieties within each planting date.