• 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
    • Nitrogen Management Experiments for Upland and Pima Cotton, 1990

      Silvertooth, J. C.; Clark, L. J.; Malcuit, J. E.; Carpenter, E. W.; Doerge, T. A.; Watson, J. E.; Silvertooth, Jeff; Bantlin, Marguerite (College of Agriculture, University of Arizona (Tucson, AZ), 1991)
      Two field experiments were conducted in Arizona in 1990 at two locations ( Maricopa and Safford). 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 fertilirystatus, and crop monitoring to ascertain crop fruiting patterns and crop N needs. Results at both locations 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 in response to the N fertilization regimes used. At Maricopa, fruit retention levels were low, petiole NO₃⁻-N concentrations relatively high, and yield responses to higher and later applications of fertilizerN were negative. At Safford, fruit retention levels were higher, petiole concentrations of NO₃⁻-N reflected strong crop demand, and a positive response to rates of fertilizer N up to 170 lbs. N/acre was measured.