Effects of Mechanical Pruning of Apple Hedgerows with a Slotting Saw on Light Penetration and Fruiting1

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.

Influence of Orchard Management Systems on Spur Quality, Light, and Fruit within the Canopy of ‘Golden Delicious’ Apple Trees

“…Apple fruit size, quality, and yield have been closely associated with the level of light in the canopy (Barritt et al, 1987;Cain, 1971;Doud and Ferree, 1980;Heinicke, 1966;Jackson and Palmer, 1977;Robinson et al, 1983). Results from this study (Tables 1, 3, and 4) support the principle that areas of canopy that receive the most light are the most productive.…”

“…Results from this study (Tables 1, 3, and 4) support the principle that areas of canopy that receive the most light are the most productive. More flowers (Cain, 1971;Jackson and Palmer, 1977), improved fruit set (Doud and Ferree, 1980), and improved spur quality (Tables 5 and 6 Barritt et al, 1987) are characteristically found in canopy areas with higher light levels and likely are related to improved fruit size, yield, and quality.…”

Influence of Orientation and Position of Fruiting Laterals on Canopy Light Penetration, Yield, and Fruit Quality of ‘Granny Smith’ Apple

“…Under New Zealand summer conditions, fruit size in 'Gala' was most severely reduced also when PPF transmission fell below *10% of full sun (16). However, these critical levels are somewhat lower than the PPF transmission levels of 30% reported from other studies (1,6,7). Very high incident light intensities in New Zealand (2200-2500 |xmol-s-1-m_2 under clear-sky summer conditions), coupled with different light measurement methods, could account for the apparently lower critical minimum light exposure levels required for efficient high production.…”

“…The transmission of light through the canopy appears to have had some influence on fruit set. All pendant laterals received < 15% of the open sky PPF, a level that is less than that reported as being sufficient for satisfactory fruit bud vigor and development (1,9). However, other factors appeared to be influencing this response, as horizontal and vertical laterals received low PPF transmission in some canopy positions (e.g., the inner canopy of the basal tier) and fruit set was not markedly reduced (Table 2).…”

“…The relationship between light interception, fruit quality, and yield of apples has been variously described (1,6,7,9,10,16,23,25). Differences in fruit tree canopy form due to pruning and training methods can substantially modify light transmission to the various regions of the canopy (3,4,11,21,24).…”