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Abstract
In horticultural research there is frequent need to consider light and temperature factors in relation to plant growth and fruiting over an extended time interval; several weeks or an entire season or more for perennial plants.
Abstract
In the mechanical harvesting of sour cherries suitable attention has been given to the rate of harvest (1,2,8), the relative cost (8) and to varying mechanical (4,5,6,8) and to cultural (2,3,7) aspects related to the physical condition of the harvested fruit. Another factor in the mechanical harvesting efficiency which is of considerable importance to the grower is the percentage of the crop borne by the tree that is removed in the harvesting process. Claypool (3) has indicated that for many species of fruit, current mechanical harvesting techniques may remove fruit within 5% of that achieved by hand-picking. Cain (1) has shown variations from 70 to 96% of crop removal for sour cherries depending on the stage of maturity and the level of nitrogen fertility. The latter figure is comparable to average hand-picking. Since the fruit left on the tree after shaking are a total loss (8) and represent a proportionate share of the total cost of production up to harvest time, the achievement of maximum crop removal is of importance in any harvesting operation.
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.
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.
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.
Abstract
Orchard density is considered as the fraction of land covered by trees at any time. Using a generalized expression for tree spread as a function of age, a general expression is derived for mean lifetime orchard density for trees of various sizes. These curves show maxima with tree sizes of 10 to 15 ft for orchard lifetimes of 24 to 40 years. Evidence is presented showing a significant negative correlation between tree size and production per unit of tree area. This regression applied to mean lifetime orchard density values shows that maximum lifetime production can be expected from trees whose final “hold spread” is 10 to 12 ft when spaced in the row at this distance with a fixed alley clearance of 8 ft.