Introduction
Canopy Management Practices means bud fruitfulness and fruit yield per node. These practices include trellis-training systems, shoot positioning, shoot orientation, shoot trimming, leaf removal in the fruiting zone, control of shoot number and spacing, and control of shoot vigor. Canopy management of fruit trees deals with the development and maintenance of their structure in relation to size and shape to obtain a yield and best quality.
In simple language it is merely the manipulation of trees canopy (all the foliage and branches) in order to provide aeration to plant for better crop production. Canopy management is one of the most important fruit plant management practice. This forms the basis of the precociousness and longevity of the fruit trees in an orchard. The strong scaffold system help the trees to produce heavy crop loads of quality fruits without any major limb breakage. Regular annual pruning is essential for the induction of good amount of new Shoot growth. which will provide the tree maximum fruit bearing area uniformly over the whole tree. Un-pruned trees grow beyond limits provided for each tree in an orchard.
Objective of canopy management
The basic objective of canopy management is to maximize light interception to optimize light distribution within canopy and to maintain proper airflow. In new plantations initial training and pruning is given to develop a strong framework of the tree whereas in old plantation the aim of canopy management is to reduce tree height and make provision of solar radiation inside the canopy by thinning excessive biomass. The objectives of canopy management are
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Maximum utilization of light
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Avoidance of built-up microclimate congenial for diseases and pest infestation
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Convenience in carrying out the cultural practices
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Maximizing productivity with quality fruit production
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Economy in obtaining the required canopy architecture
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To facilitate cultural practices
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To increase input use efficiency
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Efficient use of pesticides and fungicides
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To maintain a good balance between root and shoot growth.
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Formation of strong crotches.
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To make accessibility to machinery between rows.
Importance of canopy management
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In many fruit crops, improved production and fruit quality has come from producing more fruit from smaller trees.
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Rejuvenation of declining in productivity and fruit quality in large over grown orchards.
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Small trees are better in capturing and converting sunlight in to fruit then large trees.
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Reduction in extra expense in harvesting at large trees.
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Safety risk for the harvest (pickers) of bigger trees.
Techniques of canopy management
Pruning
Pruning has been defined as the art and science of cutting away a portion of the plant for horticultural purposes. Pruning can be used to improve tree shape, to influence its growth, flowering and fruitfulness, to improve fruit quality, to repair injury, to contain the plant and to encourage light and spray penetration. Norton (2002) reported that intensive pruning stimulated the regeneration processes as well as modified the size of tree crowns, particularly decreasing the excessive tree height. Pruning establishes the structure of the tree, its shape and form, and provides a framework.
Types of pruning
Summer pruning: The selective removal of shoots or branches during the growing season.
Dormant pruning: The same as summer pruning, except that cuts are made during the dormant season before active new growth has begun.
Summer tipping or pinching: The removal of the apical bud of shoots or spurs during the growing season.
Hedging: The indiscriminate removal of all branches within a plane, in either the summer or the dormant period
Heading cut: A cut made anywhere below the terminal bud on a shoot, but not the total removal of the shoot.
Thinning out: Total removal of the shoot or branch at its insertion point on a large branch or scaffold
Effect of pruning on yield: Results of numerous experiments indicate that pruning influences yield and regularity of bearing. The result greatly depend on tree age and growing conditions, both of which exert a simultaneous influence on tree at the time of pruning. Depending on studies, yield can be higher, similar or lower. Grubb (2002) concluded that young trees on very dwarfing rootstock will fruit even when severely pruned.
Kumar et al (2010) while studying effect of pruning on peach yield concluded that fruit yield decreases with the increase in severity of pruning. He also said that the average size and weight of fruits, i.e. length and width was significantly increased with the increased severity of pruning. The response of cultivar to different pruning level may be due to the size of leaves ad number of leaves per shoot which in turn affect the amount of the photosynthates.
Training: Basic objectives of training is to control vegetative vigour, increase light exposure for fruit/ foliage, increase air flow to prevent disease infestation and facilitate pruning and harvest methods and mechanization. While deploying the training systems, utilization of vertical and horizontal space should be taken into consideration. The choice of training system is a part of whole orchard management influencing planting distances, light interception and finally the success of the orchard in terms of obtained fruit quality and quantity. The various training methods that are used to control tree growth in many orchards are:
Delayed open centre or modified leader system: It is intermediate between the above systems. It is developed by first training the tree to the leader type by allowing the central axil to grow unpruned for the first four or five years. Then central stem is headed back and lateral branches are allowed to grow as in the open centre system.
Central leader system: In this system the central leader branches are allowed to grow independently so that it will grow more rapidly and vigorously than the side branches and tree become tall. Such tree bears fruit more near the upper portion. The lower branches are less vigorous and less fruitful.
Spindle bush system: Modification of the dwarf pyramid or intermediate between a vertical cordon and a bush form. Most important feature of this system is the laying down of lateral shoots in a horizontal position with little or no summer pruning. It is trained with or without support posts with a central leader straight and with many small fruiting branches. These branches are bent out and down by spreaders to develop wide crotches and to induce early fruiting. Tree spread is controlled by cutting back the shoots to ½ to ¾ of their length or back to weak laterals.
Overhead trellis or Bower system Bower system of training: It provides a desirable microclimate in the vine canopy and reduces the adverse effects of arid and hot weather on vine metabolism and life. In this system vines are spread over a pandal mounted at 2-2.4 m above the ground on poles made up of concrete, stone or iron.
Cordon system: This is a system where in espalier is allowed with the help of training on wires. This system is followed in vines as these are incapable of standing on their stem. This can be trained in single cordon or double cordon and commonly followed in crops like grape and passion fruit.
Kniffin system: A main stem or a vine is carried to the upper supporting wires. Renewed fruiting vines are tied. The bearing of fruiting vines are allowed to hang down. It is most adopted, easily understandable and easy to maintain. Provides higher yield and cost are effective in nature. The yield may vary hence it is important to adopt the specific system depending upon the crop.
Bending: Physically bending a branch of an apple tree results in a reduction in terminal shoot growth and a redistribution of growth hormones, particularly auxin. The stress created by bending has been shown to result in increased ethylene content in the internal air spaces within the branch. The reduced vegetative vigor in limbs that are bent reduces the production of gibberellins, which are antagonistic to flowering. The formation of moderately vigorous lateral shoots and spurs creates additional sites for flower formation. These two effects result in increased flowering and earlier fruiting. Fruit quality is also improved because of improved light penetration and because more fruit hang free instead of rubbing against the branch on more upright limbs.
Scoring, Girdling Or Ringing: Scoring and ringing, which cause the interruption of the downward flow of carbohydrates and hormones in the phloem, have been shown to alter growth and fruiting. Scoring, which is a circumscribing cut through the bark, but not into the wood, has the smallest effect. Ringing, which removes different amount of bark in a circumscribing ring, increase in severity with the amount of bark that is removed until the ultimate of tree death.
Use of growth regulators in fruit crops: Significant reduction in shoot length was observed with three sprays of Maleic Hydrazide (MH 500 ppm at leaf stage followed by 1000 ppm at leaf stage and 1500ppm at 15 leaf stage) Maleic hydrazide (MH) seemed to be more effective than CCC in increasing the cane diameter in Thompson Seedless grape (Shikhamanyand Reddy, 1989). It is found that application of cultar (25% paclobutrazol) significantly inhibited the annual shoot growth and improves photosynthetic activity which may increase yield in cherry. Application of paclobutrazol 10 g / tree in mango resulted reduced tree height (21.20%), tree volume (33.1%) and mean shoot length (48.2%). This response was attributed to GA – inhibitory activity of paclobutrazol. It was found that application of 1500 ppm CCC increased the number of fruiting buds in grape in red raspberries cv. ‘Autumn.
Conclusion
Unmanaged tree canopy not only reduces the productivity of fruits but also detoriates the quality of produce as well. It enables profitable cropping, high, regular yields and improved farm management practices, leading to higher productivity. This system of management produces high and regular yields of good quality fruits and low labour requirement to meet ever rising production costs.
References
Albarracin V, Hall A.J, Searles P.S, Rousseaux M.C. 2017. Response of vegetative growth and fruit yield to winter and summer mechanica pruning in olive trees. Scientia Horticulturae; 225: 185-194.
Avilan L, Martinez G, Marin R.C, Rodriquez M, Ruiz J, Escalante H. 2003. Square and pyramidial pruning effect on mango production. Argon. Trop; 53: 239-257
Oosthuyse S.1994. Pruning of Sensation mango trees to maintain their size and effect uniform and later flowering. South African Mango Growing Association Yearb; 14: 1-6.
Reddy N, Kurain R.M. 2011. Studies on Rejuvenation of old unproductive “Alphonso’ mango trees by pruning. Journal of horticulture science; 6: 145-147.
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