EFFECT OF PHOSPHORUS AND POTASSIUM FOLIAR FERTILIZATION ON FRUIT QUALITY OF PEARS

The influence of foliar fertilization with phosphorus (P) and potassium (K) on pear (Pyrus communis L.) fruit quality in cv. Williams was studied during the 1997 and 1998 growing seasons. The experiment comprised two treatments: foliar fertilization and an untreated control. In foliar fertilization treatment, trees were sprayed five times (from May 22 to July 7) with a foliar fertilizer, which contained 15% of P₂O₅, 20% of K₂O, 0.1% of Mn, 0.1% of B and 0.1% of Mo. We determined the contents of individual sugars (glucose, fructose, sucrose and sorbitol) and organic acids (malic, citric, fumaric and shikimic) with High Performance Liquid Chromatography (HPLC). The soluble solids as well as, the amounts of titrable acids, juice pH, main and trace elements in fruits were also measured. The foliar fertilization increased the contents of glucose, sorbitol, soluble solids, malic acid, citric acid, and potassium. Foliar fertilization showed a trend towards decreasing the contents of fructose, sucrose, fumaric acid, boron, and zinc, but had no influence on the contents of shikimic acid, juice pH and titrable acids.