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mechanical harvesting in ‘Concord’ vineyards in the early 1970s, labor for dormant vine pruning became the largest production cost ( Morris, 2007 ). Mechanical pruning or prepruning ‘Concord’ grapevine research began in the mid-1970s with the intention of

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-type pruning. Efficacy of mechanical pruning in relatively low-light environments was first tested during the 1970s by Worley (1985) in which it was concluded (based on drip-irrigated ‘Desirable’, ‘Elliott’, and ‘Farley’) that annual cuts to one of each of

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low-light environment of the southeastern United States ( Wells, 2007 ). Mechanical hedge pruning has been used successfully in high-light environments to mitigate the effects of orchard shading ( Wood and Stahmann, 2004 ) and has become the standard

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, mechanical pruning has become the most common orchard management practice to improve sunlight penetration into tree canopies. Specifically, mechanical pruning has been demonstrated in some studies to effectively increase light penetration and distribution in

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mechanical harvesting, it was proven difficult to facilitate mechanical management, such as dormant pruning ( Kurtural et al., 2012 ) and shoot removal ( Terry and Kurtural, 2011 ), with some success in mechanical leaf removal ( Cook et al., 2015 ; Yu et al

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Mature `Sharpblue' southern highbush and `Beckyblue' rabbiteye blueberry plants were mechanically pruned at two heights on three dates after fruit harvest during the 1994 growing season. No pruning had occurred for at least 3 years (`Sharpblue') or 5 years (`Beckyblue') before initiating experiment. Pruning heights were 45 and 85 cm and nonpruned for `Sharpblue' and 45 and 95 cm and nonpruned for `Beckyblue'. Pruning dates were 3, 6, and 9 weeks after peak harvest for each cultivar. Regrowth was measured in Mar. 1995 before initiation of spring growth. Pruning `Sharpblue' bushes to 45 cm increased new shoot number and mean and total shoot length but decreased fruit yield compared to the 90-cm pruning treatment. No difference in yield occurred between the 90-cm pruning treatment and the nonpruned control. As time between fruit harvest and pruning increased, new shoot number, mean and total shoot length, plant height, canopy volume, and fruit yield decreased. There was no difference in yield between the earliest pruning treatment and the control. For `Beckyblue', mean and total shoot length of regrowth and flower bud density decreased with increasing time from harvest to pruning. Yield data for `Beckyblue' were not collected in 1995 because of gall midge infestation.

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French prunes (Prunus domestica L.) on myrobalan seedling rootstock were planted in 1981 in an east-west direction with 4.9 m between rows and 2.7 m between trees on a poorly drained Class II soil in Glenn County, CA. A randomized complete block design was used with 8 trees per plot. Trees were pruned by hand to an open-center tree form or pruned by machine to a pyramid form in the dormant or summer season resulting in 6 pruning treatments. This high density system has led to high yields of good quality fruit (9.18 dry tons/acre in 1989, sized at 78 fruit per pound). Hand pruning led to higher yields, larger fruit, lower drying ratios and a greater dollar return per acre than any of the machine pruned trees. Dormant machine pruning led to larger fruit produced than those trees pruned in the summer by machine. Mechanical pruning may be possible for short time periods, but continued practice led to smaller fruit with lower yields than hand pruning. Certain locations within the tree canopy had smaller fruit size and it is within those lower locations where fruit size needs to be improved. These and additional experimental results obtained from 1987 through 1989 growing seasons will be presented.

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Abstract

Bruising of apples is a major limitation for successful mechanical harvesting and that occurring within the tree probably determines the lower limit achievable. Bruising within the tree was studied by hand shaking 50-100 fruit samples onto a catching device which virtually eliminated bruising from this source.

Internal tree structure was modified by pruning entire trees and parts of trees from 8 to 14 ft. high to minimize the number of limb impact points by falling fruit. Bruising increased with tree height under all conditions of intervening branch structure. Pruning reduced bruising less than 10% on average trees. A minimum of 15-20% bruise results from the small branches on which fruit are borne independent of height. Limited branch density counts indicate that about 90% of the potential impact points of a large tree occur on branches less than one inch in diameter, where most of the fruit are borne.

These data indicate the limitations of pruning or branch padding to reduce internal tree bruising and suggest the use of smaller trees for the most economical reduction of bruise damage during mechanical harvesting.

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Annual mechanical hedging in August or root pruning at bloom was used to control the growth of four apple (Malus domestica Borkh.) cultivars in two orchard systems planted at half the recommended in-row spacing. Trunk cross-sectional area (TCA) per hectare on the trellis system was 30% higher, a result that correlated (r = 0.80) to a 40% higher cumulative yield per hectare over 10 years compared to the central leader system. Over 10 years, the cumulative yield and TCA per hectare of `Smoothee Golden Delicious', `Empire', and `Redchief Delicious' were higher in the trellis than the central leader system, while these characteristics of `Lawspur Rome Beauty' were not influenced by orchard system. `Lawspur' had the highest TCA per hectare, cumulative yield per hectare, and greatest tendency toward biennial bearing of the four cultivars. Root pruning reduced all tree-size measurements, while hedging did not influence tree height or average shoot length. Yield and yield per TCA were reduced by hedging and root pruning, with the greatest reduction in yield caused by root pruning. Hedging increased cumulative yield per hectare with root-pruned trees intermediate between hedged standard-spaced trees. Trellis trees had a higher density of spurs and shoots and a higher leaf area index than trees on the central leader system. An evaluation of the treatment combinations using net present value analysis indicated that none of the treatments was a profitable investment. Of the top twelve treatments, as evaluated for 10 years, nine were the central leader and three the trellis system, with none of the trellis and only four of the central leader treatments being hedged or root-pruned. Results of this study indicate that orchard intensification is accomplished best by choosing appropriate planting distances and not by attempting to control growth mechanically on trees planted too close for optimum performance.

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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.

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