Effects of Foliar Boron Applications to Almond on Some Pollen Features and Fruit Set

This study was carried out to determine the effects of foliar boron (B) application on leaf B concentration, pollen viability and pollen germination rates of 'Nonpareil' and 'Drake' almond trees (Prunus dulcis), and on fruit set of artificially, open-, and self-pollinated 'Nonpareil' almond trees. The experiment was conducted in an orchard near Sanliurfa, Turkey. The B treatment rates were 0 (water-sprayed control), 250 ppm, 500 ppm and 750 ppm during 2004-2006 years. Sprays were applied at the end of autumn and at bud swelling time in spring. There was a tendency for B application to have a positive effect on pollen viability for the 'Drake' cultivar in both 2005 and 2006. In contrast, B application had no effect on pollen viability of the 'Nonpareil' cultivar in either year. Boron applications influenced pollen germination in both two years and cultivars. Boron application improved fruit set on 'Nonpareil' trees that were cross-pollinated artificially using 'Drake' pollen; however, this effect was not observed on naturally pollinated trees. Self-pollinated trees had total crop loss due to self-incompatibility. Boron application increased leaf B concentrations in both cultivars in both years. The results indicate that there is a generally beneficial effect of applying B to almond trees grown under the low soil B conditions around Sanliurfa. 'Drake' almond trees appear to be somewhat more responsive than are 'Nonpareil' trees to B application.