Trend of Calcium Concentration Changes in Fruit Peel and Effect of Calcium Nitrate Spray on Yield and Quality of Thomson Navel Orange

The aim of this research was to determine the Ca concentration in citrus fruit peel and different vegetative organs, trend of Ca changes in fruit peel during growing season and the effect of its application in phonological key stages of Thomson Navel orange in increasing relative yield and fruit quality. Ca concentration was determined in leaves, shoots, roots and the fruits of internal and external parts of canopy. Furthermore, the effects of Ca(NO3)2 foliar application after fruit set, before physiological drop and at the end of the second phase of fruit growth was evaluated using a RCBD with 4 treatments replicated four times. The results showed that fruit diameter in internal canopy was more than that in external canopy, whereas the Ca concentration in fruit peel of internal canopy (about 0.43%) was lower than that in external canopy (about 0.52%). The trend of Ca concentration changes in fruit peel of internal canopy showed more fluctuation during the growth period. The highest yield, fruit diameter, fruit weight and Ca concentration in fruit peel was obtained with Ca foliar application after fruit set and before the fruit physiological drop. According to these results, the most suitable time for Ca foliar application to enhance Ca content of citrus fruits is the first stages of fruit growth. Therefore, Ca(NO3)2 foliar application after fruit set and before the summer physiological drop is highly recommended.
Trend of Calcium Concentration Changes in Fruit Peel and Effect of Calcium Nitrate Spray on Yield and Quality of Thomson Navel Orange