Apple yield and fruit quality as influenced by boron applications

Abstract

Effect of boron (B) fertilization of ‘Elstar'’ apple trees (Malus domestica Borkh.) on yield and fruit quality was examined. The experiment was carried out during 1994–1996. ‘Elstar’ apple trees were grafted on M.26 rootstock and planted in autumn 1991 at 4x2 m apart, on sandy loam soil. In the experiment, the following B treatments were applied: (i) to the soil at a rate of 2 g B per tree, (ii) spray application of B three times before bloom at a rate of 0.67g B per tree, (iii) spray application with B after bloom at a rate of 0.67g B per tree, and (iv) apple trees without any B fertilization (control). All B treatments increased B concentration in apple fruits compared to the control. However, the most extensive increase of B concentration in fruits was observed from B sprays after bloom and soil B application. Boron sprays after bloom increased fruit set and apple yield. No significant differences between treatments in fruit weight losses during storage, number of apples infected by Penicillium sp., Monilina sp. and Botrytis cinerea were noted. Boron sprays after bloom decreased mean fruit weight, fruit firmness after storage, and increased calcium (Ca) concentration in apples, and sensitivity of fruits to bitter pit, internal breakdown, and Gloeosporium‐rot. Soil B application increased apple Ca concentration and decreased fruits with bitter pit, internal breakdown and Gloeosporium‐rot.