INTERACTION OF TREE FORM AND ROOTSTOCK ON LIGHT INTERCEPTION, YIELD AND EFFICIENCY OF 'EMPIRE', 'DELICIOUS' AND 'JONAGOLD' APPLE TREES TRAINED TO DIFFERENT SYSTEMS
In two field trials several apple training systems have been compared at the same density on the same rootstocks. In the first trial, 'Jonagold' and 'Delicious' trees on Mark rootstock were planted in 1988 at 1,111 or 1,429 trees/ha and trained to 4 systems (Slender Spindle, Vertical Axis, Y-trellis and 6-Wire Palmette Trellis). In years 3–8 there was a clear effect of tree density on yield within each system; however, despite the very different training strategies imposed on the trees, there were no significant differences in 3rd year yield among systems. In the 4th through 8th years, the Y-trellis had slightly higher yields than the other systems but the differences were not large. After 8 years, the Y-trellis had the greatest cumulative yield while there was no significant difference among the other 3 systems. Differences in yield were related to light interception. The Y-trellis had the highest light interception and the highest partitioning efficiency. Since all trees were on the same rootstock, differences in efficiency were likely the result of differences in pruning severity. In the second experiment, 'Empire' and 'Jonagold' trees were planted in 1990 on six rootstocks and trained to either Y-trellis or Vertical Axis all at the same density. There were significant differences in tree size, yield and yield efficiency due to rootstock but the two systems had very similar yields, yield efficiencies and light interception for the first 6 years. The Y-trellis trees had significantly smaller trunk cross-sectional area than the Vertical Axis trees. There was no interaction of rootstock and system. Although the systems differed in training strategy and final tree shape, they had in common an attempt to minimize pruning in the early years. These results indicate that the training system has a minor effect on tree performance as long as excessive pruning is not done.
Robinson, T. L. (1997). INTERACTION OF TREE FORM AND ROOTSTOCK ON LIGHT INTERCEPTION, YIELD AND EFFICIENCY OF 'EMPIRE', 'DELICIOUS' AND 'JONAGOLD' APPLE TREES TRAINED TO DIFFERENT SYSTEMS. Acta Hortic. 451, 427-436