No abstract

The percentage of solar radiation passing through the foliage canopy of ‘Mcintosh’ hedgerows, A) pruned annually by cutterbar and B) pruned by slotting saw, was measured continuously from pre-bloom until the completion of foliage growth in late July. Assuming the spur leaf canopy (Sp), emerges first and virtually completes growth before the shoot leaf canopy (Sh), emerges, the relative extent of Sp and Sh, and their respective interception of radiation is calculated at approximately 4-day intervals during the growing season. Even though A produced more total foliage and intercepted more total radiation, the spurs of B produced more flowers and more fruit. Spur leaf canopy B intercepted more solar radiation because of less shading by Sh. The maximum ratio Sh/Sp for adequate illumination of Sp is estimated to be about .8. The relative importance of sunlight on Sp and the time of interception of light during the growing season in relation to flower bud initiation and fruit development are discussed.

No abstract

Annual cutterbar and slotting saw hedging were compared after 3 years. Fruiting was measured as the number of spurs per twig on 3 year old growth, number of spurs flowering and fruiting, and bushels per tree. Integrated light energy quantities were measured for 6- to 14-day periods for various positions within the tree and correlated with fruiting. A hydraulic “slotting saw” mounted on a boom on a fork lift hedged a slot in the side of the tree. By cycling the slots any one position was cut only once every 4 years, permitting the regeneration of fruiting wood and the penetration of light. ‘McIntosh’ apples pruned as 10 ft high hedges with (a) cutterbar and (b) with a slotting saw, show that annual cutterbar hedging reduces the generation of new fruiting spurs, produces a dense outer periphery shading interior spurs and reduces bearing. The slotting saw mechanical pruning technique increases light penetration into the tree, produces nearly 3 times as many new spurs and about a 4-fold increase in the percentage of spurs flowering. Light measurements within the tree indicate that spur leaves require about 50% of available light for suitable flowering. Light values in trees hedged 3 years with the cutterbar were reduced to less than this value within the outer 2 ft of tree canopy where few spurs exist.