Rejuvenation of Technology in Fruit Crops
Author: P. L. Deshmukh
Canopy development of perennial crops has a seasonal as well as lifelong developmental pattern. In general, canopy of fruit crops has crowded shape. Trees of uneven shape and size are difficult to deal with and even culminate into poor fruit yield in the subsequent years as the lower branches of canopy gradually turns inert and infertile. Likewise in fruit plants also, there is a decline both in quality and quantity of produce after some years of age. As a result of which orcharding becomes economically non-viable and non-remunerative. In several areas, plantations of improved varieties having good genetic potentiality have either gone unproductive or showing marked decline in productivity. In the recent past declining productivity of old and dense orchards existing in abundance has become a matter of serious concern for the orchardists, traders as well as scientists. In fruit crop about 20-30% of the older plantations are of seedling origin embodying non-descript material and poor genetic potentiality which become senile. This is the outcome of overcrowded and intermingling of large branches and meager foliage, allowing poor light interception and utilization by photosynthetic surface to growing shoots within the canopy.
For minimizing the problem of unproductive and uneconomic orchards existing in abundance, large scale uprooting and replacement with new plantations (rehabilitation) will be a long term and expensive strategy. This renders them uneconomical. Such exhausted trees can be rejuvenated by heading back of branches for the production of new shoots, which can bear good crops in the years to come.
Technique for rejuvenating the senile orchards:
The decline of orchard trees starts with sparse appearance, yellowing and different type foliage symptoms, undergrowth and sickly appearance, dried-up top growth with small and less number of fruits. The branches of trees start to die from the top to downwards, ultimately resulted poor quality fruits (rough surface, thick skin and less juice). Such type of decline may be seen in whole orchards, on in a single tree or patches. In general, canopy of fruit crops has crowded shape. Trees of uneven shape and size are difficult to deal with and even culminate into poor yield in the subsequent years as the lower branches of canopy gradually turns inert and infertile as well.
The technology also helps in maintaining the manageable tree height with open architecture and canopy of healthy shoots with outwardly growth facilitating penetration and utilization of light. Crowding and encroachment of trees with subsequent inefficient light utilization, is an obvious problem with older orchards, if trees are not well managed. The internal bearing capacity of trees also decreases with time, due to overshadowing of internal bearing wood.
Need for rejuvenation:
Most of the fruit bearing plants are perennial in nature and provides fruit over a long period. However, productivity declines with the ageing of plants. Different factors can be attributed to this reduction in productivity:
• Poor quality of nursery plants.
• Imbalanced use of fertilizers,
• Wrong method and timing of irrigations,
• Ineffective and defective weeds control,
• Damage by insect-pests and diseases,
• Long gestation period of orchard trees,
• Defective picking and post harvest loses,
• Dominance of vegetative phase over reproductive phase.
Many orchard owners simply desert the existing orchard and go for new one. Among the various major improved technology, instead of establishment of new orchards the rejuvenation of old ones are the most important and easiest way of improving the fruit industry of India. This has several disadvantages, as it will take a long time to establish a new orchard; it is costly and will occupy a piece of land without returning significantly for long time.
However, some simple management practices can rejuvenate the old trees and make it profitable again. Vegetative propagation can accompany these practices to enhance productivity and diversity. By this time, preparation for another orchard can take place. Rejuvenation of old and unproductive orchard is best way for improving the quality and yield potential of fruit crops economically.
Strategies of rejuvenation:
• Providing technical knowledge including plant health coverage and nutritional management programme.
• Re-plantation of old & uneconomical orchards.
• Gap filling by providing disease free quality seedlings.
• Management of all the necessary inputs like plant nutrient, plant protection chemical, horticultural equipment and periodical training’s.
• Training is an important component, which improves overall efficiency of the knowledge and skill of field functionaries.
• Complete technological information on management of decline orchard may be packaged and same may be disseminated in farmer’s field.
Objectives of rejuvenation:
• To increase the productivity and economic age of plant.
• To convert the low yielding and inferior varieties/seedling origin trees into superior and high yielding trees.
• To exploit the better root system of a plant who has survived in adverse soil and climatic conditions.
• To lessen the time of gestation period.
• To increase the orchard income.
• To lessen the incidence of diseases and pests.
Principles of rejuvenation:
• Trees have latent buds which are activated by heading back of branches at certain point to put forth new sprouts which grow into branches forming fruiting area.
• When the branches are cut back, imbalance is created in root: shoot ratio as a result new shoots arise from plant to balance it.
Which points will you considered while adopting the rejuvenation technology?
• Older plantations of seedling origin which have become senile can be adopted for top worked by grafting (budding) with scion of superior varieties to upgrade seedling plantation with superior commercial varieties.
• Plantation of commercial varieties where the canopy become over crowded resulting in reduction in yield can be rejuvenated followed by canopy management.
• There is a tendency of over lapping of canopy between 10 and 12 years of age depending on the nature of variety unless the canopy is maintained by trimming and thinning in Plantations which have overlapping branches.
Manipulation of vegetative growth:
The new shoots arise on pruned branches of heading back and a few shoots are retained at proper spacing and growing towards periphery of trees. Successive removal of unwanted shoots, considering the vigour and growing direction is important. In this technique, only 4 to 6 shoots developing in outer directions on main limbs should be allowed to develop. Proper development of new canopy in horizontal direction should be kept in mind while practicing thinning of shoots. Selected shoots are further pruned out to about 50 per cent of its total length for emergence of multiple shoots below the pruning points. This was mainly done to modify the tree structure and maintain canopy size. Fruiting starts on third year after rejuvenation. Yield levels during initial year are slightly low, while the yield from third year onward is better than the unpruned trees.
SEQUENTIAL STEPS FOR REJUVENATION TECHNOLOGY
Dense, old and unproductive tree
Heading back of branches from 2.5 to 3.0 m above the ground level
Profuse emergence of new shoots on beheaded branches
Thinning of shoots (Shoot selection and regular thinning of shoot is essential for facilitating development of open and spreading canopy of healthy shoots.)
Shoot management (After shoot thinning, selected shoot are pruned up to about 50% of its total length)
Continue shoot thinning from pruned shoots up to some extend to avoid dense and bushy canopy
Fruiting starts after second year.
Rejuvenation of Old/Unproductive Guava Orchards:
A procedure to rejuvenate and restore the production potential of old unproductive and wilt affected orchards has been developed, which employs pruning of branches at different periodicity and at different severities. Crowding and encroachment of guava trees with subsequent inefficient light utilization is an obvious problem with older orchards, if trees are not well managed. The internal bearing capacity of guava trees also decreases with time, due to overshadowing of internal bearing wood.
The rejuvenation technology involves cutting of exhausted trees (showing marked decline in annual production) to the extent of 1.0 to 1.5 meter height above the ground level during May with the objective of facilitating new shoots. The newly emerging shoots are allowed to grow up to a length of about 40 to 50cm which could be attained in 4-5 months of pruning.
These shoots are further pruned out to about 50% of its total length in October to facilitate emergence of multiple shoots below the pruning point. Profusely emerging shoots in the inner canopy are also pruned out to promote branching. The multiple shoots developed as a result of October pruning are capable of producing flower buds for the rainy season crop.
Those farmers keen to harvest the rainy season crop can allow the shoots to bear buds and fruits. However, as the winter crop has more marketing edge and value due to quality with the onset of rainy crop, shoot pruning (50 percent) is done again in May. This procedure of sequential and periodic pruning is continued every year for proper shaping of tree canopy and to ensure enhanced production of quality fruits during winter season.
Rejuvenation of Old Mango Orchard:
In mango, 40-45 years old trees exhibit decline in fruit yield because of dense and overcrowded canopy. These trees do not get proper sunlight resulting in decreased production of shoots. New emerging shoots are weak and are unsuitable for flowering and fruiting. The population of insect-pests and the incidence of diseases increased in such orchards.
These unproductive trees can be converted into productive ones by pruning them. Intermingled, diseased and dead branches are removed. Thereafter, undesirable branches of unproductive trees are marked. At the end of December, these marked branches are beheaded at 1.5 to 2.0 meter from distal end and the cut portions are pasted with copper oxychloride solution. During March-April, a number of new shoots emerged around the cut portions of the pruned branches. Only 8 to 10 healthy and outward growing shoots are retained at proper distance so that a good frame-work is developed in the following years.
These rejuvenated trees are fertilized with 2.5 kg urea, 3.0 kg single superphosphate and 1.5 kg M.O.P. per plant. The half dose of fertilizers is applied in the month of February and the other half at the end of June. The plants are irrigated at an interval of 15 days especially in the months of April, May and June for healthy growth of new shoots. In the first week of July, 150 kg of compost per tree is also applied. Unwanted emerging new shoots are regularly removed to maintain the tree canopy. It also helps in getting proper nourishment to retained shoots. After two years of pruning new shoots come into bearing and the yield of fruit increases gradually. Thus, old and unproductive trees are converted in to productive ones.
Management practices to be followed after rejuvenation:
• Marking of the tree with white chock for rejuvenation pruning.
• After marking cutting should be done from lower surface of the branch and later from upper surface to avoid cracking as well as bark splitting.
• Application of cow dung or copper oxychloride on cut surface to check the microbial infection.
• Ploughing of rejuvenated orchard and preparation of basin and irrigation channel.
• Application of FYM @ 40-50 kg per plant soon after rejuvenation.
• Insure irrigation soon after rejuvenation for shoot sprouting and proper development of tree canopies.
• Mulching around the tree with black 100 micron polyethylene film (100 micron equal to 400 gauge).
• Care of only emerged shoots
• Thinning of shoot and retaining only 4 to 6 outward growing, well-spaced and healthy shoot per pruned branch.
• Good phytosanitary procedures are to be adopted to manage the rejuvenated plants.
• Regular observations for incidence of stem borer. Pull out the caterpillar (trunk borer) mechanically by inserting iron spoke in the shelter holes.
• Remove the insects and insert the swab of cotton soaked in monocrotophos and plug the holes with mud.
For overcoming the problem of unproductive and uneconomic orchards existing in abundance, large scale uprooting and replacement with new plantations (rehabilitation) will be a long term and expensive strategy. Therefore such exhausted fruit trees can be rejuvenated by pruning / beheading and top working technique. Old unproductive plantation of commercial varieties can be rejuvenated followed by canopy management. While senile older plantations of seedling origin can top worked by grafting with scion of superior varieties to improve the genetical status and yield potential.
Orchard establishment is a long term process and cannot be done in days but once the yield is reduced to such an extent that orcharding becomes non-economical, rejuvenation is said to be essential as it:
• Helps in restoring the production potential of old unproductive and diseased orchards in shortest possible duration than any other technique.
• Helps in maintaining the manageable tree height and canopy with open architecture.
• Sustaining the life of farmer without affecting his economy to a great extent.
About Author / Additional Info:
P. L. Deshmukh
Ph.D. Scholar, Department of Horticulture,
Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola, Maharashtra