Articles
LIGHT INTERCEPTION, YIELD AND FRUIT QUALITY OF ‘EMPIRE’ AND ‘DELICIOUS’ APPLE TREES GROWN IN FOUR ORCHARD SYSTEMS.
The systems were: 1. Slender Spindle/M.9, 2. Central Leader/M.9/MM.111 (Interstems), 3. Central Leader/M.7, (CL) and 4. Y-trellis/M.26.
During the first 5 years, yields for ‘Empire’ were positively correlated with tree density.
In the second 5 years the Y-trellis had the highest yields while yields of the other three systems continued to be a function of tree density.
With ‘Delicious’ during all 10 years, the Y-trellis had the highest yearly yield despite lower tree density than the slender spindle.
The yields of the other three systems were primarily a function of tree density during the first 10 years.
Total light interception as measured by fisheye photography was highest with the Y-trellis in the second five years and was the basis for the higher mature yields.
The higher light interception of this system was the result of the canopy architecture which allowed the tree canopy to grow over the tractor alleys.
With the three pyramid shaped systems the requirement of tractor alleys did not allow for such high levels of light interception.
In addition to higher light interception the Y-trellis had the highest efficiency of converting light energy into fruit.
The importance of the higher level of mature yield with the Y-trellis on profitability was estimated.
Fruit size was a function of cropload; however, the Y-trellis system had the potential to produce very large yields per hectare yet maintain the same fruit size as the slender spindles.
Fruit color and quality were primarily a function of light distribution within the canopy of each system.
Pruning had a large effect on canopy light distribution as even the small trees became too dense in the seventh year.