• Comparison of Three Irrigation Scheduling Methods and Evaluation of Irrigation Leaching Characteristics

      Scherer, Tom; Slack, Don; Watson, Jack; Fox, Fred; Silvertooth, Jeff; Bantlin, Marguerite (College of Agriculture, University of Arizona (Tucson, AZ), 1991)
      Three methods were used to schedule irrigations during the 1990 growing season on replicated plots at the Maricopa Ag Center using DPL 90 cotton. This is the final report of the research initiated in 1988. The three methods were: a soil water balance model based on historic consumptive use curves (ERIE), a soil water balance model (AZSCHED) based on the Modified Penman Equation and daily weather (AZMET), and infrared thermometry using the Crop Water Stress Index (CWSI). A potassium- bromide conservative tracer was applied at selected sites in the plots to evaluate leaching characteristics. The irrigation scheduling test was again duplicated at the Safford Experiment Station and is presented in another report. Results from this years data indicate that there was no significant difference in yield between the 3 methods. Also, there was no significant difference in the amount of applied irrigation water. The AZSCHED and ERIE methods will be developed into Extension educational tools and released for use by growers.
    • Irrigation Scheduling on Long and Short Staple Cotton Safford Agricultural Center, 1990

      Clark, L. J.; Carpenter, E. W.; Scherer, T. F.; Slack, D. C.; Fox, F. Jr.; Silvertooth, Jeff; Bantlin, Marguerite (College of Agriculture, University of Arizona (Tucson, AZ), 1991)
      Three irrigation scheduling techniques are compared on both long and short staple cotton in replicated small plot trials on the Safford Agricultural Center. The Erie method uses historical evapotranspiration data developed in the Mesa area but mathematically adjusted for the elevation in Safford and incorporated in a computer spreadsheet. The AZSCHED method is a near real -time irrigation scheduling program using AZMET weather date, a modified Penman equation and heat unit based crop coefficients to calculate water deficits. This program will schedule irrigations on up to 60 fields. The third method utilizes infrared thermometry to determine crop water stress indices from foliage temperatures, ambient temperature and relative humidity. This latter method was used to track the crop stress throughout the growing season on all treatments. All three methods were considered successful for both long and short staple cotton with the Erie method yielding higher than the other two for both types of cotton. Further refinements will be made on the AZSCHED method until it performs at or above the Erie method
    • Water Stress Effects on Upland Cotton Lint Yields Using Infrared Thermometry to Schedule Irrigations

      Husman, S. H.; Garrot, D. J. Jr.; Moore, M.; Silvertooth, Jeff; Bantlin, Marguerite (College of Agriculture, University of Arizona (Tucson, AZ), 1991)
      The Crop Water Stress Index (CWSI) was used to schedule irrigation on D + PL 90 cotton on a large scale commercial basis in Waddell, Az. The test consisted of sixteen one acre surface irrigated plots. There were four treatments with four replicates arranged in a randomized complete block design. Highest lint yields were attained when irrigations were scheduled at 0.28 CWSI units.