EFFECT OF APPLE TREE SPACING AND SUMMER PRUNING ON LEAF-AREA DISTRIBUTION AND LIGHT INTERCEPTION

Light interception and leaf area distribution were measured on four planting systems of cultivar 'Golden Delicious' and cultivar 'Karmijn de Sonnaville' on M.9 rootstock at tree densities ranging from 2000 to 8333 trees ha-1. Leaf area index (LAI) varied from 1.4 for 'Golden Delicious' at 2000 trees ha-1 to 3.3 at 8333 trees ha-1. For the same trees, light interception increased from 49 to 83%. Yield was closely related to light interception. Trees at the more rectangular arrangement of 2.75 m x 0.8 m intercepted less light than trees at 2.0 m x 1.25 m, despite the latter having a lower tree density. Summer pruning reduced the leaf area by 10-30% and light interception by 6-14% (based on the pre-summer pruning level). Leaf dry weight per unit area was closely related to irradiance within the canopy.