• Chemical Freeze Protection of Citrus 1987/1988

      Butler, M.; Brown, P.; Fallahi, E.; Butler, Marvin (College of Agriculture, University of Arizona (Tucson, AZ), 1988-12)
      Research has shown that the presence of ice-nucleation-active (INA) bacteria, such as Pseudomonas syringae and Erwinia herbicola, will result in ice formation several degrees centigrade higher than would otherwise occur. Seven possible chemical frost protectants were applied to Lisbon lemons of the Yuma Mesa Ag Center. Four replications of effectiveness of the materials were evaluated by determining tip bum and fruit damage following two subfreezing episodes in December 1987. There were no statistically significant differences between treatments under the conditions of this study.
    • 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.