Effect of foliar boron application on olive (Olea europaea L.) fruit set and yield

Boron is an essential element for higher plants and its fundamental role in plant vegetative growth and reproductive process is clearly recognised. Several studies report its crucial function in improving flower fertility and fruit setting percentage in olive. Deficiencies phenomena, responsible also for suboptimal yield, are observed in olive groves and are sometimes not identified. As recent studies have shown that B is mobile in the phloem of all species that utilize polyols as a primary photosynthetic metabolite, such as olive, then B deficiencies may be treated with foliar applications. The aim of the present research was to evaluate the efficacy of a foliar fertiliser containing B in increasing fruit set and yield in olive. The study was carried out in 2004 on an olive orchard, cv. Leccino, located in Southern Italy (BR), during a bearing year. A control was compared to a B fertilised treatment that received two foliar applications with a product containing 9 g B 100 g-1, at 270 mg B L-1, in pre and post anthesis. During the crop cycle, the fruit setting percentage, on 2 plants per plot and 2 shoots per cardinal direction and, at harvesting, the main quantitative yield parameters were determined. Total number of flowers and fruits per shoot varied significantly with shoot length and canopy exposition. Neither fruit set nor yield were influenced by B foliar application. Average values of 4.29 and 4.65%, for fruit set percentage, and 32.2 and 30.6 kg olives per plot, for yield, were recorded, respectively for treated and not treated plants. Further research is needed to evaluate the efficacy of different application timing and amounts and to assess plant response in low fruit load years.