Ground applications of ZnO to large mature pecan [Carya illinoinensis (Wangenh.) K. Koch] trees in orchards possessing an acidic soil, but with a culturally induced slightly alkaline soil surface zone, were at least as effective as was ZnSO4 for rapidly correcting severe foliar Zn deficiency, improving in-shell nut production, and maintaining kernel quality. Under such soil conditions, light disking of Zn applied at 160 kg·ha-1 from ZnO elevated foliar Zn above the sufficiency level by the second growing season after application; whereas an absence of disking delayed substantial uptake from ZnO until the fourth growing season. ZnO, usually a lower priced Zn source, was as effective as was ZnSO4 for correcting Zn deficiencies via broadcast ground application; however, same season correction of Zn deficiency was best accomplished by the standard practice of using foliar sprays of ZnSO4 rather than by heavy soil applications of either Zn source.
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