Fallspray of Nitrogen, Zinc, and Boron and Their Effect on Fruit Set of Peach Trees

In order to increase the storage of nitrogen, zinc and boron of peach trees and its effect on flowering and fruit set, an experiment was conducted in a randomized complete block design with seven treatments and four replications for three years (2015-2018) on 56 trees with the same age and size trees in the east of Mazandaran. Treatments included: 1) control, 2) Urea (10 gL-1), 3) Urea (10 gL-1) + Zinc sulfate (5 g.i-1), 4) Urea (10 g.l-1) + Zinc sulfate (5 g.l-1) + Boric acid (5 g.l-1), 5) Urea (15 gL-1) + Zinc sulfate (5 gL-1) + Boric acid (5 gL-1), 6) Urea (20 g.L-1) + Zinc sulfate (5 gL-1) + Boric acid (5 gL-1), and 7) Urea (25 g.L-1) + Zinc sulfate (5 gLl-1) + Boric acid (5 g.L-1).   The results showed that urea was quickly absorbed by leaves, so that nitrogen concentration in leaf tissue increased shortly after spraying. The measuring trend of nitrogen concentration at different times in foliar spray treatments showed that nitrogen concentration in leaf tissue increased initially and then began to decrease again. Therefore, in treatments 7, nitrogen concentration at 4, 24, and 48 hours after spraying increased from 2% before spraying to, respectively, 3.15%, 3.07%, and 2.06%. That indicates the absorption and then removal of nitrogen from the leaf tissue. Zinc concentrations in the leaves increased in all treatments by foliar spray of zinc sulfate, and this trend of absorption and increase of zinc concentration in the leaf tissue lasted for 48 hours after spraying. Boric acid foliar spray also increased the concentration of boron in the leaf tissue, such that the concentration of boron in the leaf tissue reached the maximum after 4 hours, and then decreased gradually. Results showed that fallspray treatments were effective in increasing fruit set and reducing abscising fruitlets, and this increase in fruit set was statistically significant. However, treatment seven that accelerated leaf loss had the highest effect on fruit formation, and was about 50% higher than the control. Therefore, to increase the fruit set and reduce the flower and fruitlets drops, applying treatment 7 in autumn, when 10-15% of the leaves are yellow, is recommended.