• Development of Best Management Practices for Fertigation of Young Citrus Tree

      Thompson, Thomas L.; White, Scott A.; Walworth, James; Sower, Greg; Wright, Glenn; Kilby, Mike (College of Agriculture, University of Arizona (Tucson, AZ), 2002-02)
      'Newhall' navel oranges on 'Carrizo' rootstock were planted in Mar. 1997 at the Citrus Agricultural Center. The objectives of this experiment were: i) to determine the effects of N rate and fertigation frequency for microsprinkler-irrigated navel oranges on tree N status, and crop yield and quality; and ii) to develop Best Management Practices which promote optimum tree growth and production while minimizing nitrate leaching. The trees are equipped with a microsprinkler irrigation system. The experiment is a randomized complete block factorial with N rates of 0, 0.15, 0.30, and 0.45 lb N/tree/year, and fertigation frequencies of weekly, monthly, and three times per year. Unfertilized control trees are also included in the experimental design. Each of the ten treatments is replicated five times. The trees were harvested for the first time in Feb. 2001. Fruit were processed through an automatic fruit sizer, and fruit from each plot were further evaluated for fruit quality. Although unfertilized control trees had lower leaf N content than fertilized trees, fruit yield and quality of controls was no lower than fertilized trees. Similarly, there were few statistically significant differences in fruit yield and quality between trees receiving different N rates and fertigation frequencies.
    • Development of Best Management Practices for Fertigation of Young Citrus Trees, 2002 Report

      Thompson, Thomas L.; White, Scott A.; Walworth, James; Sower, Greg; Wright, Glenn; Gibson, Rick (College of Agriculture, University of Arizona (Tucson, AZ), 2002-11)
      'Newhall' navel oranges on 'Carrizo' rootstock were planted in Mar. 1997 at the Citrus Agricultural Center. The objectives of this experiment were to i) determine the effects of N rate and fertigation frequency for microsprinkler-irrigated navel oranges on tree N status, and crop yield and quality; and ii) develop Best Management Practices which promote optimum tree growth and production while minimizing nitrate leaching. The trees are equipped with a microsprinkler irrigation system. The experiment is a randomized complete block factorial with N rates of 0, 0.15, 0.30, and 0.45 lb N/tree/year, and fertigation frequencies of weekly, monthly, and three times per year. Unfertilized control trees are also included in the experimental design. Each of the ten treatments is replicated five times. The trees were harvested in Jan. 2002. Fruit were processed through an automatic fruit sizer, and fruit from each plot were further evaluated for fruit quality. Leaf N concentration was responsive to N rate, but not to fertigation frequency. Leaf N in all fertilized plots was above tissue critical levels. Fruit yield in fertilized plots was higher than in unfertilized plots, but, in fertilized treatments, there was no significant effect of N rate or fertigation frequency on fruit yield or quality.
    • Development of Best Management Practices for Fertigation of Young Citrus Trees, 2003 Report

      Thompson, Thomas L.; White, Scott A.; Walworth, James; Sower, Greg; Wright, Glenn (College of Agriculture, University of Arizona (Tucson, AZ), 2003)
      ‘Newhall’ navel oranges on ‘Carrizo’ rootstock were planted in Mar. 1997 at the Citrus Agricultural Center. The objectives of this experiment, conducted during 2000 - 2003, were to i) determine the effects of N rate and fertigation frequency for microsprinkler-irrigated navel oranges on tree N status, and crop yield and quality; and ii) develop Best Management Practices which promote optimum tree growth and production while minimizing nitrate leaching. The trees were equipped with a microsprinkler irrigation system. The experiment was a randomized complete block factorial with N rates of 0, 0.15, 0.30, and 0.45 lb N/tree/year, and fertigation frequencies of weekly, monthly, and three times per year. Each of the ten treatments was replicated five times. The trees were harvested in December or January of each growing season. Fruit were processed through an automatic fruit sizer, and fruit from each plot were further evaluated for fruit quality. Leaf N concentration and fruit yield of 4-6 year old trees were responsive to N rate, but not to fertigation frequency. Fruit quality and packout were not significantly affected by either N rate or fertigation frequency. Fruit yield was optimized at annual N rates of 0.25 lb/tree (four-year-old trees) to 0.35 lb/tree (six-year-old trees) during this experiment. We propose new tissue guidelines for guiding N fertilization of young microsprinkler-irrigated navel oranges.