Effect of foliar nutrition of 'Page' mandarin on preharvest fruit splitting, ‎polygalacturonase activity and yield traits

Preharvest fruit splitting of citrus is a physiological disorder that every year in susceptible cultivars such as 'Page' mandarin, reduces the marketable crop and increases the fungal infection of fruits in orchard and storage. Due to the role that three elements potassium, calcium and boron can play in the strength of citrus peel, a research was performed based on randomized complete blocks design to determine the effects of single foliar application of 'Page' mandarin trees with different ratios of three minerals: potassium nitrate (1 %), calcium nitrate (1 %) and boric acid (0.5 %) at the end of June drop on severity of splitting, polygalacturonase activity and yield traits. The results showed that the treatments did not affect the activity of polygalacturonase, but reduced the splitting percent from about 12.3 % to 8.3 % and increased tree yield, fruit weight and juice percent of fruits. Based on the findings, the lowest splitting was observed in calcium-containing combined treatments. Potassium-containing treatments had the highest yield, fruit weight and juice content. Therefore, 'Page' mandarin producers can be recommended to foliar application of trees by a combination of all three elements of potassium, calcium and boron at the end of June drop to reduce the splitting percent and improve the quantity and quality of production.