A multi-disciplinary effort combining horticultural, chemical and chemicalengineering expertise culminated in the development of a new coated crystallized fertilizer mixture with a non-destructive and long-lasting foliar delivery system. This product was intended to meet a variety of plant nutritional needs. In the present study Olive-Nutri-Vant, a variant of the product, was tested for spring application to olive at the pre-bloom stage to promote olive yield and the yield and quality of olive oil. The mineral constituents of Olive-Nutri-Vant are: N(NH2), 10%; P 2O5, 33%; K2O, 21%; B, 1.8%. Applications were carried out in March about three weeks before bud opening in olive orchards in locations with various environmental conditions in Israel and southern Italy. At the initial stage three treatments were tested: untreated control, Olive-Nutri-Vant, and a non-coated fertilizer mixture plus triton B 1956 as surfactant. The results clearly showed an increased mineral level in the leaves of Olive-Nutri-Vant treated trees as compared to the other two treatments. In a more advanced stage of the study, large-scale field trials extending over at least one or two hectares each were carried out. A significant increase in yield was registered for Olive-Nutri-Vant as compared to the other treatments in 90% of the plots. The olives of each treatment were extracted separately, and oil percentage was found to vary between the treatments. Olive oil yield per plot was always higher in the Olive-Nutri-Vant treated trees due to the higher yield of olives. When olive oil quality was compared, no differences could be distinguished in any of the parameters, including the fatty acid profile. In view of the poor nutritional status of most olive trees, we suppose that foliar fertilization with a nutrient mixture with lasting action, carried out mainly in spring before blooming, would increase olive yield in most cases.