Effect of drip boron fertigation on yield and fruit quality in a high-density apple orchard

This study was carried out in 2001-2003 at the Experimental Orchard of the Research Institute of Pomology and Floriculture, Skierniewice, Poland, on mature 'Jonagold' apple (Malus domestica Borkh.) trees (M.26 EMLA) planted at 4 x 2.5 m spacing on a sandy loam soil with low boron (B) availability. The trees were drip fertigated with B at rates of 0.5, 1, or 1.5 g tree- 1 over 4 weeks at 3-d intervals beginning at the stage of bud break. Plants that did not receive B via drip irrigation system served as a control. Drip B fertigation effectively increased water-soluble B concentrations in the soil and the status of this microelement in leaves of current season shoots. However, the B fertigation had no effect on tree vigor. In 2 out of 3 years, the drip B fertigation improved flower B status, fruit set, and yield. The efficiency of the drip B fertigation was not influenced by B rate. In all growing seasons, the drip B fertigation increased B level and a soluble solids concentration in the fruit flesh, but had no effect on mean fruit weight, color, titratable acidity, and fruit firmness. It was concluded that on coarse-textured soils with low B availability, the drip B fertigation of mature apple trees in high-density orchards can be recommended from the stage of bud burst to petal fall at a rate of 0.5 g tree- 1.