• Conservation Tillage Effects on Infiltration and Irrigation Advance Times

      Martin, E. C.; Adu-Tutu, K. O.; McCloskey, W. B.; Husman, S. H.; Clay, P.; Ottman, M.; Tronstad, Russell; Husman, Steve; Norton, Randy; University of Arizona, Tucson, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 2005-05)
      Field experiments were initiated at sites in Marana, Coolidge and Goodyear, Arizona, in the Fall of 2001, in a cotton-based, conservation tillage project. In the 2002 cotton season, following cover and grain crops, soil and water management assessments were made to evaluate the impact of conservation tillage on surface irrigation performance. An additional site was added in the winter of 2002 at Maricopa, Arizona. Analyses included soil texture, infiltration rate and water advancement. At Coolidge, the Conservation plots had higher infiltration rates and longer advance times than the Conventional plots in 2002, 2003 and 2004. At Marana, infiltration rates were initially higher for the Conservation plots but the rates converged at the end of four hours in 2002. In 2003, the Conventional plots infiltrated about one inch more and the opposite occurred in 2004, where the Conservation plots infiltrated about 1 inch more than the Conventional. The advance times for Marana showed the water in the Conventional wheel rows to be the fastest. At Goodyear, the Conservation plots infiltrated more than the Conventional plots in 2002. This also resulted in a slower advance time for the Conservation plots. In 2003, due to tillage by the grower, treatment effects could not be compared and the site was abandoned in 2004. At Maricopa, the Conservation plots infiltrated almost 2.2 inches more water than the Conventional plots and the water reached the end of the field three hours ahead of the fastest Conservation plot in 2003. In 2004, the Conservation plot infiltrated just over 1½ inches more water than the Conventional plots with the Conventional plots having faster advance times. Seasonal irrigation water applications to each treatment were relatively equal for all the sites with the exception of Coolidge. Here, the long field combined with sandy soil made it difficult to adequately irrigate the Conservation plots. In 2002, an additional 21 inches of water was applied to the Conservation plots. In 2003, that amount was reduced to 12.5 inches. The 2004 irrigation data are not yet available. The yield data show a significant difference between years and different sites. In 2002, only the yields measured at Coolidge were significantly different with the Conservation yielding higher than the Conventional. This may have been due to the increase water application. In 2003, the opposite occurred and the Conventional plots yielded more than the Conservation plots. This may have been due to herbicide damage. At Maricopa the Conventional plot also yielded more than the Conservation plot in 2003 but there was no measured difference in 2004. The Marana site had equal yields for both treatments except for the final year, 2004, when the Conventional yielded higher than the Conservation treatment. Indications are that conservation tillage does impact irrigation performance and it may not be suitable for all locations depending on soil type and field layout.
    • Evaluation of Irrigation Termination Effects on Yield and Fiber Quality of Upland Cotton, 2004

      Silvertooth, J. C.; Galadima, A.; Tronstad, R.; Tronstad, Russell; Husman, Steve; Norton, Randy; University of Arizona Cooperative Extension (College of Agriculture, University of Arizona (Tucson, AZ), 2005-05)
      A field experiment was conducted in 2004 at the University of Arizona Maricopa Agricultural Center (1,175ft. elevation) to evaluate the effects of five irrigation termination (IT1, IT2, IT3, IT4, and IT5) dates on yield and fiber micronaire of several Upland cotton varieties. In addition, the economic relationships of IT treatments were also evaluated. The first IT treatment (IT1) was made with the intention of terminating irrigations somewhat pre-maturely. Based upon current UA recommendations for IT to complete a single cycle fruit set, the more optimal date of IT would have included one or two additional irrigations (beyond IT1). In this experiment, IT2 was structured to provide an additional (one) irrigation before the more optimal date. For the IT3 plots, the intention was to attempt to time termination to match the conventional growers optimal date. The IT4 and IT5 were imposed to attempt to produce a second cycle fruit set and irrigations continued until 27 August and 21 September respectively. In general, lint yield and micronaire results revealed significant differences among the IT treatments. In a similar fashion to 2000-2002 IT experiments, micronaire and lint yield values consistently increased with later IT dates. The best micronaire and lint yield results were achieved with IT4 date, which received 12 in. less irrigation water than IT5. The 12 in. water saved equates to approximately 20% of the total water used under the conventional practice. The average marginal value of water for all Upland varieties in going from IT1 to IT2, IT2 to IT3, IT3 to IT4, and IT4 to IT5 using November 2004 prices and low carrying costs is calculated at $320.07, $150.15, $100.54, and -$28.16 per acre-foot of water. If steeper mike discounts (November 1999), a lower base lint price (45¢/lb.), and higher costs (i.e., more costly insecticide and chemical costs) are imputed to extend the crop, the marginal value of an acre-foot of water for all Upland varieties and replications in going from IT1 to IT2, IT2 to IT3, IT3 to IT4, and IT4 to IT5 is estimated at $164.04, $48.15, $12.97, and -$94.79. Profitability and marginal value of water sometimes vary quite markedly between different varieties and termination dates as well.
    • Evaluation of Plant Population Effects on Lint Yield and Fiber Quality

      Norton, E. J.; Tronstad, Russell; Husman, Steve; Norton, Randy; La Paz and Mohave Counties (College of Agriculture, University of Arizona (Tucson, AZ), 2005-05)
      The cotton (Gossypium spp.) plant is a true perennial with perhaps the most complex structure of all the major field crops. Plants can compensate to a large degree for environmental as well as physical conditions. Much research has been conducted to arrive at plant population recommendations that optimize the yield and quality of the crop. Research conducted in the low desert regions of Arizona suggest that optimum plant density lies somewhere between 25,000 and 50,000 plants per acre. However, cotton crops with plant densities outside of this optimal range still have the ability to yield similarly and maintain premium quality. Accordingly, a research project was conducted comparing four separate plant densities. Objectives included determining effects on yield and fiber quality. The study was laid out in a randomized complete block design with target plant populations of approximately 30K, 50K, 70K, and 90K plants per acre as the treatments. All other inputs were equal across treatments. Throughout the course of the season, plant measurements showed no distinct differences among the treatments. Height-to-Node ratios (an indicator of vegetative tendencies) remained above normal throughout the season for all populations. Fruit retention levels remained optimal throughout the season. Lint yield results revealed that treatment four (90K plants per acre) yielded significantly less that the other three treatments. No significant differences in fiber quality were observed among treatments.
    • 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.