Below normal zinc (Zn) foliar levels, as well as visual symptoms of Zn deficiency in leaves, shoots and fruit are commonly observed in ‘Hass’ avocado orchards in the municipalities of Tepic and Xalisco, Nayarit. The research was undertaken from 2001 to 2005 in two commercial non-irrigated ‘Hass’ avocado orchards in the municipality of Tepic. The objective was to assess the effect of foliar or soil zinc sulphate (ZnSO4) applications on Zn foliar levels, as well as on yield, fruit size and fruit form. Orchard soil was of light texture, pH 5.8 and low Zn content (1.4 to 3.13 mg·kg-1). Tree canopy sprays treatments were applied using 8 L water·tree-1 and were: a) a single spray of 4,056 g ZnSO4·L water-1 (1.46 g Zn), and b) two sprays of 2.028 g ZnSO4·L water-1 (0.73 g Zn); both treatments delivered 11.68 g Zn/tree. Soil treatments were annual and consisted of: a) single application of 1.5 kg ZnSO4 (35.5 % Zn)·tree-1, and b) two applications of 0.75 kg ZnSO4·tree-1 each. Control trees were let untreated. ZnSO4 foliar sprays were ineffective to correct foliar Zn deficiency and had no positive effect on yield and fruit size. Two soil applications of 0.75 kg ZnSO4·tree-1year-1 were effective to increase yield, fruit size and fruit form (more elongated), decreasing the production of small and round fruit. This treatment also increased Zn levels in leaves and fruit pulp. A poor relationship between ZnSO4 soil rates tested and Zn leaf content was found.

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