In 1986, an orchard systems trial was planted with `Empire' and `Jonagold' on M.26 rootstock to compare the performance of the Y-trellis training system at a range of spacings and rectangularities. There were four in-row spacings ranging from 90 cm to 3.66 m and four between-row spacings ranging from 3 to 6 m, giving tree densities from 472 trees/ha up to 3588 trees/acre. Rectangularities ranged from 0.83 to 6.67. In several cases, different spacings gave the same tree density, but with different rectangularity. Trees were trained to a Y-shaped trellis with a 60° angle. Scaffold branches were trained to the wires on each side of the Y in a fan-shaped arrangement. At the closest in-row spacing only two scaffolds were allowed per tree, while at the widest in-row spacing up to 12 scaffolds were allowed per tree. At the end of 11 years, tree weight and cumulative yield per tree were negatively correlated to tree density, while light interception and cumulative yield per hectare were positively correlated to tree density. However, the relationship was weakened by differing results with different rectangularities at the same spacing. As rectangularity increased at a given density, tree size, yield, and light interception were reduced. However, at the lower densities, trees failed to completely fill the trellis when rectangularity was low, thus limiting yield per hectare. Fruit red color was reduced at the highest densities and increased with increasing rectangularity.
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