ERFORMANCE OF Y-SHAPED APPLE CANOPIES AT VARIOUS ANGLES IN COMPARISON WITH CENTRAL LEADER TRAINED TREES.
Six-year cumulative yields of the Y-shaped trees were generally greater than those of the central leader-trained trees. Exceptions were the most horizontal and the most vertical canopy angles, which had the lowest yields. The relationship between angle of Y arms and yield showed a broad optimum between 50° and 70° above the horizontal. The difference in yield between Y-shaped trees and central leader trees was greater for ‘Empire’ than for ‘Delicious’, where differences were small. At the optimum angle, ‘Empire’ yielded from 16% to 40% more than the central leader trees, while ‘Delicious’ yielded from 7% to 18% more, depending on the spacing. ‘Empire’ fruit size was smaller from the Y-shaped trees than from the central leader trees, but with ‘Delicious’ the reverse was true. There was no consistent optimum angle for best fruit size. Fruit red color was best at the most vertical angle.