CANOPY MANAGEMENT OF FRUIT CROPS
Authors: A.K. Goswami, A. Nagaraja, Jai Prakash and Madhubala Thakre
IARI, New Delhi-110012
Fruit production involves the capturing and conversion of sunlight into production of fruit biomass (dry matter content). The main controlling factors are amount of incoming radiation, and percentage of radiation intercepted by tree canopies. The productivity of fruit crops depends on several factors, poor management of canopy architecture being the most important one. The canopy management, particularly its components like tree training and pruning, affects the quantity of sunlight intercepted by trees, as tree shape determines the presentation of leaf area to in coming radiation. An ideal training strategy centres around the arrangement of plant parts, especially, to develop a better plant architecture that optimizes the utilization of sunlight and promotes productivity. The basic principles in canopy management are:
• Maximum utilization of light.
• Avoidance of built-up microclimate congenial for diseases and pest infestation.
• Convenience in carrying out the cultural practices.
• Maximizing productivity with quality fruit production.
• Economy in obtaining the required canopy architecture.
The canopy development in perennial fruit crops has a seasonal and lifetime developmental pattern. The sum of development over individual season results in the final canopy dimension and form. In general, most of the fruit orchards are not managed by initial training and pruning that is why with ageing, the trees attain taller size and huge structure, thereby leading to higher cost towards orchard management. The basic problems with overcrowded orchards are non availability of sufficient light, more incidences of pests, etc. Generally, farmers are not aware of the importance of tree architecture and canopy management, as well as their related techniques. As a result, a majority of trees attain tall or curved growth structure and canopy marked with criss-cross branches, leading to a dense vegetative growth with very poor infiltration rate of active radiation. Such conditions not only affect the photosynthetic rate but also facilitate proliferation of pests. Consequently, for want of due care of tree canopy architecture and pressures of pest abundance and poor photosynthetic efficiency over the years, the trees turn senile.
The development of unproductive orchards in vast stretch in fruit belts has become a common sight. In fact, fruiting potential of the trees is largely governed by their architecture, canopy density and photosynthetic efficiency. Canopy management in fruit crops deals with the development and maintenance of their structure in relation to the size and shape for maximum productivity with quality fruits. Tree canopy management, especially size control, has become a priority for reducing production cost and increasing fruit yield and quality. Canopy design and shape influence light interception with assured higher monetary returns to fruit growers. Therefore, early height control and tree canopy management are important techniques which should be practised in fruit crops for higher returns to growers. The orchards/plantations since their establishment need regular and scientific canopy management to facilitate proper development of strong upright framework of trees with outwardly spreading canopy.
Canopy management is the manipulation of tree canopies to optimize the production of quality fruits. The canopy management, particularly its components like tree training and pruning, affects the quantity of sunlight intercepted by trees, as tree shape determines the presentation of leaf area to incoming radiation. An ideal training strategy centres around the arrangement of plant parts, especially, to develop a better plant architecture that optimizes the utilization of sunlight and promotes productivity. Canopy management depends on the nature and growth pattern of plant, number of plants / ha and pruning techniques. The removal of unwanted parts of plant is thus known as pruning. The practice of pruning, as and when performed in an appropriate manner, keeps the plant in such shape and condition as to yield fruits of desired quality. There are two main physiological effects when trees are pruned i.e. reduction of bud number leading to changes in dominance relationships, and changes in canopy lighting with respect to the former, it stands to reason that pruners should only remove dead, diseased, out of place wood or weak wood. Pruning should be done when trees are young to establish their basic shapes and sizes, and continued as trees mature. In commercial orchards, pruning facilitates normal daily operations. Where trees have outgrown their allotted space, pruning can increase the bearing surface. Trees that grow too close together shade out the lower canopy portions and in turn decrease their fruit setting and pruning allow light to reach the top and lower sides of trees resulting increased bearing surface and more fruit setting. Pruning is done either to encourage the growth (thinning) or to reduce the tree size (heading back). Thinning of bearing trees encourages vegetative growth, and removes interior branches, encouraging the outward growth into the allotted area planned for mature trees to occupy. Heading back reduces the outward canopy growth through topping and hedging of branches.
CANOPY MANAGEMENT PROCEDURES
Trees have been pruned in many ways; some better than others. The closer the pruning method fits the natural growth habit of the trees, the more effective, efficient, sustainable and sensible it is. It is wise to work with trees, and not against them. The first cuts made to the tree are the most important. It is worth doing this correctly from the start, and not delaying pruning until large cuts have to be made. The rule is, as soon as a branch is seen to be out of place, train it or remove it. How one defines "out of place" is the key, since pruning must be selective, meaning one cuts away only dead, diseased, and dysfunctional branches, of whatever size is deemed appropriate. One aims to do so each year, in the right season, and to never prune more than is necessary. The rule is simple i.e. do the right things at the right time to the right trees. The guiding principles apply to trees of all ages. The aim is to induce trees to produce a balance of vegetative and fruiting wood, with uncrowded bearing wood situated conveniently within the relative shelter of the well-lit, adequately ventilated inner tree canopy and low enough to harvest from the ground. The canopy management strategies manage tree complexity through induction of complexity in young trees, maintenance of complexity in bearing trees and reduction of complexity of large, old trees declining due to the effects of age and/or shading.
Procedure of canopy management in Guava:
The growth habit of the tree, its response to pruning, harvesting method and other cultural methods should be considered before the planting of any crop. Guava bears crop on current season growth. Guava can be pruned and trained into a large, low hanging bush to permit hand harvesting or into a small tree with a single trunk to permit mechanical harvesting. Untrained or unpruned guava trees become huge and unmanageable after a few years of growth. The bearing area is reduced and the interior of plants become entirely without fruits. Trees are topped to a uniform height of 60-70 cm from the ground level, 2 - 3 months after planting to induce the emergence of new growth below the cut points. Three to four equally spaced shoots are retained around the stem to form the main scaffold limbs of tree. These shoots are allowed to grow for 4-5 months after topping until they attain a length of 40 - 50 cm. The selected shoots are further pruned to 50 per cent of their length for inducing multiple shoots from the buds below the cut end. Newly emerged shoots are allowed to grow up to 40-50 cm and pruned once again for emergence of new shoots. This is chiefly done to obtain the desired shape. The pruning operations continue during the second year after planting. After two years, short branches within the tree canopy produce a compact and strong structure. Pruning is performed in April-May every year.
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