Effect of boron fertilization of apple trees (Malus domestica Borth.) on yield and fruit quality

Aim of this work was to examine effect of boron fertilization on yield of apple trees and fruit quality. The experiment was carried out during 1994-1996 in Dąbrowice Experimental Orchard belonging to Research Institute of Pomology and Floriculture in Skiemiewice, on Š a m p i o n cultivar, grafted on M26 rootstock. Trees were planted in the autumn of 1991 at the distance 4 x 2,5 m, on sandy-loam soil. Before starting and during carrying out the study there were not visual symptoms of boron deficiency. In the experiment applied boron fertilization to the soil at the dose 2 g B per tree or three times boron sprays before or after bloom at the dose 0,67 g B per tree. Apple trees without any boron fertilization were served as a control. Results of experiment showed that only boron sprays after bloom increased fruit set and yield. There were no significant differences between treatments in fruit maturity at harvest, fruit weight losses dunng storage, apple number infected by Penicillium, Monilina and Botrytis cinerea. Boron sprays after bloom increased firmness of apples after storage and decreased sensibility to bitter pit, internal breakdown and Gloeosporium-rot. All boron treatments increased boron concentration in apples in comparison with control ones. However, the highest increase of boron concentration in apples was observed when boron sprays were done after bloom and soil boron application. Only boron sprays applied after bloom increased calcium concentration in apples