Effect of boron fertilization of 'Dabrowicka' prune trees on growth, yield, and fruit quality

The aim of this study was to examine the effects of different modes of boron (B) fertilization of prune trees (Prunus domestica L.) on growth, yield and fruit quality. The experiment was conducted in 1996-1998 in the Experimental Station of the Research Institute of Pomology in Skierniewice, Poland on 'Dabrowicka' prune trees grafted on Myrobalan (Prunus divaricata L.) seedlings. Prune trees were planted on sandy loam soil with low hot-water extractable B concentration. Four experimental treatments were applied: (i) soil B application at a rate of 2 kg B ha(-1) applied in early spring as Bortrac fertilizer (16% B as boric acid), (ii) sprays with B in spring at a rate of 0.67 kg B ha(-1) spray applied at the beginning of flowering, petal fall and 2 weeks after full bloom, (iii) spray with B in autumn at a rate of 2 kg B ha(-1) applied about 3 weeks before natural leaf fall, and (iv) control-trees without B fertilization. The results showed that B applied to the soil and as leaf applications in spring and autumn had no effect on total length of one-year-old shoots per tree, however, all B treatments increased the number of current shoots per tree and decreased their length. In two years of the study, B applications increased the density of flowers on the shoots which led to increasing yield. Application of B was without influence on fruit set and mean fruit weight. All modes of B fertilization increased fruit B concentration and decreased firmness and titratable acidy of fruit at harvest. LeafB applications in spring and autumn decreased sensitivity of prune fruit to cracking and increased fruit soluble solids contents, however, those effects were also dependent on the particular growing season.