Second Generation Apple Systems Trials
Tree size as measured by trunk cross sectional area was also not influenced by training system. However, when looking at the increase in tree growth in 2012 compared to what occurred in 2011 when all the trees were cropping there was an interesting phenomena. In 2011 the actual tree girth increase for the Jonagold/B.9 was about 3.8 cm2. In 2012 when there was no crop load on the tree the average tree girth increase for these same trees was about 7.8 cm2—more than 100% greater than the previous year—which is what would normally be expected in comparing cropping versus noncropping trees. However, the Fuji trees did not show the same trend. Average tree girth increase in 2011, the cropping year, was about 7.3 cm2; in 2012 the average increase in girth was about 10.5 cm2 which is only just under a 50% increase in growth increment. This suggests the possibility that cropping on B.9 trees may be more debilitating than it is on M.9 trees.
Based upon the system and the activity, labor requirements varied. Except for shoot pinching in the Fuji the relationship for each variety was the same within a variety. Spring pruning was greatest on the TT system and not different between the others. Since only the TS and A are shoot pinched it is a task only associated with those systems. The TS, A and TT systems are summer pruned to maximize sunlight into the trees. In 2012 the TS required the highest labor hours followed by the TT and then the A; MP is not summer pruned. Like previous years the TT required the most total labor but it was not significantly different from the TS.
• April: Spring prune and tie trees to wire; with MP, thin branches and shorten branches with mainly large cuts
• Mid-July: Pinch shoots in upper part of A and TS systems
• Late July early August: Summer prune Jonagold and Fuji, tie down branches in the TS
Tree training systems are primarily used to manipulate sunlight to maximize exposure of the canopy and fruit. One way to measure light levels is to measure the percent full sunlight that reaches the lowest levels of the canopy in comparison to the light levels in the drive rows, or that which is not obstructed by the tree canopy. Therefore, the lower the % sun the denser the canopy and less light. Sunlight levels are measured with a one meter long line quantum sensor. Light levels were measured on two occasions under uniform light conditions during the solar noon hours. Measurements were taken just prior to summer pruning and after summer pruning in mid-August.
In the Jonagold %FS was not influenced by training system either before or after pruning except that it was higher after summer pruning. There was an influence on the change in %FS after pruning with significantly higher sunlight in both the TT and TS systems. The increase in the A system was not as great. In Fuji %FS was higher prior to and after summer pruning for the TT than the other systems. The change in light levels was also greatest for the TT.
After the 5th growing season (2012) total yield in bushels/acre for Jonagold was greatest for trees in the MP and lowest for those in the TT system. Cumulative efficiency was greatest for the MP system but not significantly better than the trees in the TS system. Training system had no influence on yields or efficiency for Fuji.
In a previous trial (Crassweller & Smith, 2002) that included Low Trellis Hedgerow instead of HT, yields were higher for the A but as to be expected lower in the Low Trellis due to a smaller canopy volume.
ReferenceCrassweller, R., D. Smith 2002. Apple training system trials – 2001. PA Fruit News 82(2): 53-58.