The Effect of Foliar Application of Urea and Iron Chelate on Fruit Set,Yield, Quality and Nutritional Indices of Grape

Fertilization is one of the most important management principles in modern viticulture, which plays a major role in improving of the vine- grower's economy with a direct impact on productivity and the final quality of both fruits and raisins. Foliar application is one of the fast and effective methods for meeting plants nutrition requirement, especially in the critical stages of growth. In this study the effect of iron chelate (Fe-EDDHA) and urea, each in three levels of 0, 0.5 and 1% was evaluated in ‘Sultana’ grapevine in a 10-years old vineyard under a factorial desing based on  randomized complete block in Bahareh village of Malayer city, west of Iran, in 2016. Trees were sprayed  during three stages, including of one week befor flowering and two and five weeks after corolla abscision. The fruit harvesting was done in mid-September based on maturity index for measurement of certain qualitative and quantitative characters of fruits. The highest fruit set percentage and yield was achieved in 1% urea in combination with 1% Fe and the lowest of these indices were observed in control plants. Moreover, urea and iron chelate, and their interaction, significantly (P ≤ 0.01) influenced total soluble solid (TSS), titratable acidity, total phenol, anthocyanin and ascorbic acid in ‘Sultana’ grapevine fruits. The maximum TSS of berry was obtained with 1% Fe solely or in combination with urea at 0.5% and 1% concentrations, indicating the key role of Fe in TSS increasing of berry. Flavonoid and total phenol contents were higher in the presence of 0.5 and 1% of Fe, compared to other treatments. The highest anthocyanin content was achieved with application of 0.5% of Fe. The results showed that while application of urea and iron in 1% concentrations are necessary for a greater fruit yield, a higher quality of fruit is brought about with  application of urea at a moderate concentration in combination with Fe at the highest examined level.