Vegetative and Reproductive Responses of Apple Trees to Zinc Fertilization under Conditions of Acid Coarse-Textured Soil

Abstract

ABSTRACT The aim of this study was to examine response of apple (Malus domestica Borkh.) trees to zinc (Zn) fertilization under conditions of acid coarse-textured soil with low 1M hydrochloric acid (HCl)-soluble Zn level. The experiment was carried out during 2004-2005 at a commercial orchard in Central Poland on mature ‘Jonagold’ apple trees/M.26 EMLA, planted at a spacing of 4 × 2.5 m. The trees were sprayed with Zn: (i) prebloom, at the stage of silver tip, and tight cluster at a rate of 140 and 100 g ha− 1, respectively, (ii) postbloom, at the stage of petal fall, and 2 weeks later at a rate of 80 g ha− 1 in each spray treatment, and (iii) postharvest, 4–5 weeks before the natural leaf fall at a rate of 500 g ha− 1. Other trees were supplied with Zn to soil at a rate of 3 kg ha− 1. In all the studied treatments, Zn was used as ethylenediaminetetraacetic acid (EDTA). Trees unsupplied with Zn served as the control. Tree vigor, fruit set, yield and fruit quality at harvest (mean fruit weight, firmness, color, russeting, soluble solids concentration, and acidity) were not influenced by Zn fertilization. Postharvest Zn sprays slightly damaged leaf tissues but did not cause defoliation. Soil Zn application raised Zn concentrations in flowers, and leaves 28, 56, and 84 days after petal fall. Pre- and postbloom Zn sprays increased Zn status in flowers and leaves 28 days after flowering, respectively. The obtained results indicate that Zn fertilization of ‘Jonagold’ apple trees with Zn status in mid-summer leaves and flowers of 17 mg kg− 1 and 27 mg kg− 1, respectively, is not successful in improving vigor and tree yield.