Foliar Application of Potassium and Boron during Pomegranate (Punica granatum) Fruit Development Can Improve Fruit Quality

The aim of this work was to evaluate the effects of different concentrations of K and B foliar application on fruit quality parameters of pomegranate fruit (Punica granatum). To achieve this objective, in 2007 a trial was carried out in a pomegranate orchard located in Ferdows region, Iran. The plants were sprayed with three K (0, 1.5, and 3 gㆍL-¹ potassium metalosate) and three B (0, 1.5, and 3 gㆍL-¹ H₃BO₃) concentrations, in a complete randomized design with three replications; spraying was replicated three times during fruit development stage. Foliar application of K and B significantly increased the content of K and B in the leaf (P less-than or equal to 0.01), and peel and juice of fruit (P less-than or equal to 0.05). The fruits of trees fertilized at the highest K concentration had higher titratable acidity and total soluble solids than those in the other treatments. Foliar K application at 1.5 and 3 gㆍL-¹ significantly (P less-than or equal to 0.05) increased the content of anthocyanins, phenolic compounds, and antioxidant activity of fruit juice. Application of K at 3 gㆍL-¹ alone decreased the fruit firmness significantly, while the spraying of B at 3 gㆍL-¹ increased the fruit firmness significantly. Content of ascorbic acid increased significantly with increasing of K concentrations and the highest content of ascorbic acid observed in the treatment of combination of K and B at high concentration. Foliar B application significantly (P less-than or equal to 0.05) increased the peel percentage of fruits, while it decreased significantly (P less-than or equal to 0.05) the juice percentage. K application at 3 gㆍL-¹ alone and with combination of B applications showed the highest significant content of total sugar content. Electrolyte leakage of fruit peel decreased significantly (P less-than or equal to 0.05) by foliar K application compared with no K fertilizer application.