تلخیص
A field study was conducted on sweet orange (cultivar “Red Blood”) orchard of a farmer at Shahbaz Garhi, Mardan to evaluate the effect of foliar spray of Zn, Mn and B on the fruit yield and leaf nutrient concentrations as well as to diagnose their critical levels. Zinc, Mn and B alone and in various combinations were applied as foliar spray in the form of sulfate salts and boric acid @ 0.4, 0.2 and 0.04 kg ha-1, respectively dissolved in 400 liters of water. Leaf samples were analyzed for different micronutrients and fruit yield was recorded. Foliar sprays of Zn, Mn and B significantly increased fruit yield. Leaf concentrations of Zn and Mn were also increased with the foliar spray of the respective micronutrients but leaf B was not significantly influenced by B spray. Critical levels of Zn, Mn and B in leaves were found to be 22, 25 and 29 mg kg-1, respectively. It may be concluded that the levels of leaf concentrations of Zn, Mn and B mentioned above serve as guide for the nutrient status of sweet orange trees. Trees require foliar application with the relevant micronutrient when its leaf concentration goes down the critical level.