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University of Arizona (2021)

Zinc Management and Salt Tolerance of Pecan in Arid Regions

Smith, Cyrus

Titre : Zinc Management and Salt Tolerance of Pecan in Arid Regions

Auteur : Smith, Cyrus

Université de soutenance : University of Arizona

Grade : Master of Science (MS) 2021

Résumé partiel
In the alkaline, calcareous soils common to the southwest zinc reacts with hydroxyl and carbonate groups forming compounds of low solubility, reducing its plant availability, and making soil application of zinc oxide (ZnO) or zinc sulfate (ZnSO4) impractical. Therefore, foliar application of zinc in southwestern pecan orchards is common practice. Fertigation with zinc-ethylenediaminetetraacetic acid (Zn-EDTA) is a possible alternative that has shown positive results in alkaline, calcareous soils. However, many growers fertigating their orchards with Zn-EDTA are still using supplemental zinc foliar sprays due to lack of confidence that soil applied Zn-EDTA can supply enough zinc to the trees. We conducted an experiment to determine if the application of foliar zinc sprays to ‘Wichita’ pecan trees already receiving zinc in the form of Zn-EDTA through fertigation would increase photosynthesis rates. We applied zinc sulfate monohydrate (ZnSO4·H2O), ZnSO4·H2O + Urea Ammonium Nitrate (UAN), Zn-EDTA, water alone, and water + UAN to seven ‘Wichita’ pecans growing in alkaline, calcareous soil in San Simon, AZ. Applications were made twice in 2018 and twice in 2019, Zn-EDTA was applied only in 2019. Photosynthesis measurements were taken approximately two to four weeks following each application. Mid-day stem water potential was also measured to verify that water stress was not limiting photosynthesis. Our results showed that photosynthesis rates were not increased by the application of supplemental foliar zinc sprays in trees fertigated with Zn-EDTA with mean leaf zinc concentrations of untreated leaves in the range of 16-21 mg·kg-1. We concluded that photosynthesis was not zinc limited and that no additional benefit was conferred with regard to photosynthesis from the application of supplemental foliar zinc sprays.Another problem for pecan growers in the southwest is high salt content in the soil. Very little experimentation has been conducted to determine pecan response to saline-sodic conditions. To contribute to this research, we performed an experiment with seven rootstock pecan seedlings grown in alkaline, calcareous, saline-sodic soil at the Safford Agricultural Center in Safford, AZ.

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