During this period, management of tree resources expands to include initial development of fruiting sites and the initial phase of flowering, as well as continued expansion of tree structure to fill allotted space. Heavy pruning can delay the filling of the allotted canopy within the orchard by reducing total shoot number and total shoot growth. Pruning severity can also delay flowering, as flower cluster number decreases as pruning severity increases. Research indicates that pruning should be minimized in order to maximize the potential for early flowering and fruiting. In order to encourage branching, limbs may be positioned at desirable angles.
In addition, bagging of the central leader of apple is useful in some cultivars to encourage a higher number of shoots to develop. The practice also increases the number of flower clusters and subsequent number of fruit. Notching immediately above buds is another technique for increasing lateral development. Notching is equally effective on all sections of the limb, with over 90 percent of notched buds developing into shoots. This effect has the highest impact in the basal and middle sections of the limb where natural lateral branching occurs less frequently. The production of fruit has a tremendous impact on shoot growth and future fruit production. There is a limited supply of resources within the tree for growth. With the presence of fruit, there is a decrease in the supply of resources available for shoot and root growth. As a result, shoot and root growth will decrease relative to the level of fruit production.
Mature, Bearing Trees
After a tree's desired canopy size has been attained, management begins to focus on the maintenance of fruiting sites to provide sustained flower and fruit production along with the annual expansion of associated shoot growth. The focus is on merging the appropriate pruning and training techniques necessary to maintain tree size while keeping vegetative growth in balance with the need to maximize fruit quality and yield efficiency. Appropriate pruning cuts are used primarily to remove weak, unproductive wood and enhance light penetration into the canopy; ideally, pruning and training techniques are utilized to maximize continual development of fruiting wood throughout the tree canopy. Maintenance and renewal of fruiting sites are critical to sustained fruit quality as a tree ages. Additional pruning focuses on the prevention or removal of excessive shoot growth that can develop in localized areas and reduce light penetration into the canopy. For example, removal of strong, upright water sprouts within the canopy of mature peach trees approximately four weeks prior to harvest increases fruit size and flower bud formation (Figure T2.2).
Growth and development in tree fruit are regulated by certain basic biological processes. Training and pruning practices have a significant impact on the balance between vegetative growth and reproductive growth. An understanding of the biological principles that govern growth and development as well as the basic principles underlying the effects of pruning and training will permit the orchardist to balance vegetative and reproductive growth in the most efficient, effective, and practical manner.
Related Topics: CARBOHYDRATE PARTITIONING AND PLANT GROWTH; CULTIVAR SELECTION; DWARFING; FLOWER BUD FORMATION, POL-
FIGURE T2.2. Effect of preharvest water sprout removal (WSR) on packout of 'Redskin' peach (Source: Modified from Myers, 1993.)
LINATION, AND FRUIT SET; LIGHT INTERCEPTION AND PHOTOSYNTHESIS; PLANT GROWTH REGULATION; PLANT HORMONES; ROOTSTOCK SELECTION; TRAINING SYSTEMS
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Tustin, S. (1991). Basic physiology of tree training and pruning. Proc. Wash. State Hort. Assoc. 87:50-63.
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