Response of apple to soil applied zinc

The response of apple Gala var. on MM106 rootstocks to applied Zn on acid soil was investigated during five years in two commercial orchards in the State of Parana Brazil. The soil in both sites was an Inceptisol with topsoil reaction of about 4.5 and 0.1N HCl extractable Zn < 3 ppm. Granular ZnSO4. H2O was applied by broadcasting on the soil surface around each tree and in two concentrated holes (5 cm diameter by 10 cm deep) around each tree, one time only at two rates: 17.5 and 35.0 g Zn/tree. There were no significant differences in leaf-Zn concentration and fruit yields during the first year of the experiment. After two years, placement of Zn-fertilizer in holes significantly increased leaf-Zn and fruit yields. This treatment continued to be effective until the end of five years experiment, correcting the symptoms of Zn deficiency. As the Zn rate was increased, the leaf-Zn also increased. Surface-Zn treatment was not effective at either site.