• Analysis and Evaluation of the Performance of Surface N-Fertigation on the Yuma Mesa

      Sanchez, C. A.; Zerihun, D.; Wright, Glenn; Gibson, Rick (College of Agriculture, University of Arizona (Tucson, AZ), 2002-11)
      The application of N-fertilizers mixed with a surface irrigation stream (surface N-fertigation) is widely practiced in the Yume Mesa. Guidelines for the efficient management of surface N-fertigation systems are needed. The purpose of the work reported herein is to evaluate the relative effectiveness of existing surface N-fertigation management practices in the Yuma Mesa. This has been accomplished through the following steps: (1) a complete set of performance indices that can be used to assess the relative merit of alternative management scenarios are identified and defined and Equations as well as solutions for quantifying the performance indices are proposed; (2) surface fertigation field experiments (using Br- as a tracer) were performed in two irrigation basins at the Yuma Mesa research farm of the University of Arizona during the fall season of 2000; (3) the spatial distribution as well as the application efficiency and adequacy of Br- applied with irrigation water was determined using the performance functions proposed herein; and (4) the results were analyzed to assess the merits and limitations of existing practices.
    • Efficient Irrigation and N Management for Lemons: Results for 1993-1996

      Sanchez, C. A.; Wilcox, M.; Wright, G. C.; Brown, P.; Wright, Glenn (College of Agriculture, University of Arizona (Tucson, AZ), 1997-11)
      Studies are being conducted which aim to improve the efficiency of irrigation and N fertilization for lemons produced on sandy soils in the low desert The first experiment evaluates the response of 'Lisbon' lemons to various flood irrigation intervals. Irrigation intervals are based on soil moisture depletion (SMD) as calculated from frequent neutron probe soil moisture measurements. Individual treatments were irrigated when total SMI) was 25 %, 40 %, 55 %, and 70 %, respectively. The second experiment compares the performance of young lemons produced under flood, trickle, and micro-spray irrigation systems. The third experiment evaluates the response of young lemons to water and N combinations (3 by 3 factorial) under micro - spray irrigation. The three irrigation rates were targeted for 30 cnbar, 20 cnbar, and 10 cnbar tension. The three N rates were 0.1, 0.2, and 0.4 kg N/tree. One flood irrigation treatment was added for comparative purposes. Overall, results obtained in experiment 1 during 1994, 1995, and 1996 indicate optimal fruit growth and yield is obtained at approximately 40% SMD. The results of experiment 2 show that after 3 years, only micro-jet irrigation produced less tree growth than flood irrigation. In 1995, first year fruit yields were significantly greater for pressurized irrigation compared to flood irrigation. However, by 1996 there were no differences in yield to irrigation treatment. Results from experiment 3 show a linear response in tree growth to irrigation. In 1994 and 1995, tree growth at the high micro - spray soil moisture regime was significantly greater than trees irrigated by flood. However, in 1996 where we failed to increase the micro-spay irrigation time to meet the increased water demand by the trees, the flood irrigation regime was superior. Yields were also increased to irrigation. There were no significant differences in tree growth to N fertilization rates in 1994 and 1995. However, there was increased tree growth in 1996 and a yield increase to N fertilizer rate at the highest soil moisture regime.
    • Efficient Irrigation and Nitrogen Management for Lemons: Results for 1993-1995

      Sanchez, C. A.; Wilcox, M.; Wright, G. C.; Brown, P.; Wright, Glenn (College of Agriculture, University of Arizona (Tucson, AZ), 1996-09)
      Studies are being conducted which aim to improve the efficiency of irrigation and N fertilization for lemons produced on sandy soils in the low desert. The first experiment evaluates the response of 'Lisbon' lemons to various flood irrigation intervals. Irrigation intervals are based on soil moisture depletion (SMD) as calculated from frequent neutron probe soil moisture measurements. Individual treatments were irrigated when total SMD was 25 %, 40 %, 55 %, and 70 %, respectively. The second experiment compares the performance of young lemons produced under flood, trickle, and micro -spray irrigation systems. The third experiment evaluates the response of young lemons to water and N combinations (3 by 3 factorial) under micro -spray irrigation. The three irrigation rates were targeted for 30 cnbar, 20 cnbar, and 10 cnbar tension. The three N rates were 0.1, 0.2, and 0.4 kg N /tree. One flood irrigation treatment was added for comparative purposes. Overall, results obtained in experiment 1 during 1994 and 1995 indicate optimal fruit growth ,and yield is obtained at approximately 40% SMD. The results of experiment 2 show that after 18 months micro -spray irrigation produced significantly more tree growth than flood and drip irrigation methods. Additionally, first year fruit yields were significantly greater for pressurized irrigation compared to flood irrigation. Results from experiment 3 show a linear response in tree growth up to 10 cnbar soil moisture tension. Furthermore, tree growth at 10 cnbar tension was significantly greater than trees irrigated by flood. Yields were also increased to irrigation regime. There were no significant differences in tree growth to N fertilization rates. However, there was a yield increase to N fertilizer rate at the highest soil moisture regime.
    • Response of Micro-Sprinkler Irrigated ‘Lisbon’ lemons to N Rate and Source on a Superstition Sand

      Sanchez, C. A.; Peralta, M.; Wright, Glenn (College of Agriculture, University of Arizona (Tucson, AZ), 2003)
      Much of the citrus produced in southwestern Arizona is grown on sandy soils. Because these soils have a low ion exchange capacity, are highly permeable to water, and are prone to nitrate leaching, achieving efficient N management presents a continuing challenge. Studies were conducted during 1999, 2000, and 2001 to evaluate the response of micro-sprinkler irrigated lemons to N rate (0, 1.8, and 3.6 kg N tree-1 yr-1) and N source (UN32, CAN-17, CN9, and mixed program) on Superstition Sand. Lemon yield increased by N rate during the first and second harvests in 1999, 2000, and 2001. In 1999, yields increased linearly to 3.6 kg N tree-1 yr-1 but in 2000 and 2001 yields were maximized at 1.8 kg N tree-1 yr-1. In 1999 where larger increments of N were applied over a smaller time period relative to the other seasons, UN32 seemed to decrease yields at the highest N rate. There were no significant effects to N source in 2000 and 2001.