|Tree Management Systems for Profitable Mango Production|
|A. Introduction - Planting Mango|
|B. Management of Young Trees|
|C. Management of Bearing Trees|
|D. Management of Biennial Bearing|
Mango Tree Management
How to Select a Mango Variety
Selection of Orchard Sites
Land Preparation, Irrigation and Drainage Layout
The purpose of this document is to describe and explain various issues related to mango tree management. An attempt is made here to present the reader with the principles behind mango tree management and to build a conceptual framework for developing a tree management system for mango cultivation so that a mango grower can himself/herself devise a management system for his/her orchard taking into account the conditions of the orchard site and resources available for his enterprise.
This document briefly covers the basic aspects in mango management from site selection and land preparation to variety selection, planting, caring young and then bearing trees, pruning, training and finally a brief description on plant protection aspects. Pest and disease control measures are not discussed in detail as these information are well documented elsewhere.
You are invited to read the whole document at first, however briefly, to get a broad general understanding of how the different operations come together. Then over time re-read the individual sections in greater depth for specific information.
If a scientific tree management package as detailed in this document is adopted, it may be possible for one to act to avoid the problems in the orchard rather than reacting to them after the problems come up. You and the nature need to run your orchar d rather than allow the orchard to run you. To do this, it is imperative to understand the whole issue of tree management and how each small bit of information on management aspects meshes together. Then the mango cultivation will become a pleasure and a relaxation instead of a drudgery.
The author gratefully acknowledge Dr. S.B.D.G. Jayawardena, Director, Horticulture Research and Development Institute, for his encouragement and guidance extended to him during the preparation of this document. He wishes to extend his appreciation to Mr. Y.P. de Silva for providing with him a lap top computer for word processing.
Mango cultivation in the world is expanding due to the popularity of this fruit and ever increasing demand for fresh and processed mango products. Hence, there is also a great potential to expand our mango cultivation in Sri Lanka. However, a profitab le mango industry depend on the production capacity of trees. Trees must be in a position to produce sufficient quantity of fruits every year. To achieve this status, trees must be managed, whether it is in a home garden or in a commercial scale orchard, using a proper tree management system.
Before we embark on growing and managing trees, it is indispensable that at first everybody has a good understanding about this crop -Mango and its range of available varieties. Therefore, let us briefly examine what is mango and mango varieties first .
Mango is an evergreen tree grown under tropical and subtropical environments around the world. It is botanically named as Mangifera indica and is a member of family Anacardiaceae. There are mainly two types of mangos classified according to the place of origin, monoembryonic mangoes or Indian varieties of subtropical origin and polyembryonic mangoes, varieties of tropical origin. Monoembryonic varieties were evolved in subtropical India while the polyembryonic mangoes were originated in wet tropical south east Asia. Over the years, these varieties have been moved from place to place around the world and cultivated. Because of the cross pollination nature of mango flowers, new varieties have been evolved as a result of natural and man made crosses wi thin and between these two groups of mango. Thus a range of widely differing varieties have been appeared over the last few decades. Out of these varieties, superior candidates giving high yields and quality fruits were adopted as cultivars ( Cultivated Varieties) in mango growing regions of the world. The best of these have been mass propagated with vegetative means and well established and famous cultivars have been born in different regions of the world. These cultivars show very distinct differences in relation to yields, bearing habits, fruit size, color, flavor and aroma etc.. Another important feature of these cultivars is that they are very sensitive to the growing environment, meaning changes in environmental factors severely affect the produc tivity and fruit quality of cultivars.
When it is established in the field, mangoes grow vegetatively for some time and then acquires the bearing capacity. Usually, mangoes propagated by grafting or other vegetative methods take 3 - 4 years to bear while trees coming from seedlings take a longer period. The fist phase of growth is known as Vegetative Phase and after trees start bearing fruits trees enter the Reproductive Phase.
During the vegetative phase of growth, plants produce several growth flushes a year and the tree canopy is expanded. In vegetatively propagated plants, at young age flowering may occur. Otherwise, after about 3 - 5 years, trees turn to reproductive ph ase of growth.
After that, in the reproductive phase, trees tend to show well defined, seasonal and cyclic growth patterns which are interrelated and interdependent. It is essential to study more about this as it is one of the criteria that is utilized to manage tre es. Growers must learn to recognize the importance of this growth cycles or tree phenology as it is known in horticulture science. Onece the growth patterns are identified and understood, cultural management decisions to improve the tree productivity may be made with confidence.
Basically, three types of mango growth patterns are explained in order to understand mango phenology.
Flushing or Emergence of New Shoots
Dormancy or Rest Period
Flowering and Fruit Set
This refers to the emergence of new shoots on the terminals of old shoots. Major flush takes place just after harvesting of fruitsor a little later. The role of the flushing is to enlarge tree size and to produce leaves for utilizing sun light to prod uce carbohydrates by photosinthesis to support fruit development in the following season.
Though mango needs only one full growth flush per year to produce the best yields, usually mango has a tendency to produce more shoot flushes than it is actually required especially when the water and nutrients are not limiting and environmental tempe ratures are higher than normal for the particular variety. Therefore skillful control of the growth of shoot flushes has the greatest impact on the tree productivity.
Dormancy or Rest
Mango trees must undergo a period of rest or dormancy, a period with out any externally observable growth activity in mature shoots after flushing, for about 3 - 5 months depending on the variety. This is a pre condition required for the successful fl owering. This dormancy may be naturally induced by low temperatures in most sub tropical environments and soil moisture deficits under tropical conditions and may be by both ways under some situations. Low N supply also tend to promote this rest in matur e shoots. Though the term dormancy or rest is used to explain this stage of growth, plants are not actually in a dormant stage physiologically. At this time plants very actively photosynthezise and produce carbohydrates for storage to be used in the foll owing season.
High temperature, high soil moisture and high N levels in the soil or in tree tissues might break this rest and force the tree to flush again and again. This will affect the physiology of trees by changing the food reserve base and will lead to a furt her vegetative bias. Trees under such conditions produce poor crops during the following fruiting season. This happens more often when varieties used to rest under low temperature climates are planted under high temperature environments.
Flowering and Fruit Set
During the rest period tree carbohydrate reserves levels increase as against tree N level. Thus C:N ratio of the trees increase. Also at the same time, shoots bolecules required to make flower primodia on the terminals of mature shoots. When all these conditions are accomplished the mature shoots become physiologically ready for flowering. After this stage is achieved trees are ready to flower when the environment is appropriate for flowering.
After flowering, fruit set takes place as a result of pollination of compleate flowers. Mango has two types of flowers, Complete Flowers or hermaphrodite flowers having both male and female organs i.e. anthers and overy, and male flowers having only anthers producing pollen. Soon after pollination and fertilization of the overy with pollen fruits start to develop. Then the plant become active in translocating carbohydrate and other food reserves from the storage tissues such as roots and trunks to th e developing fruits for their growth.
Though mango flower panicles produce thousands of flowers and a lot of these pollinate, only a few, in some varieties one fruit per panicle while in other varieties several fruits per panicle, commence further development. Then the size of the crop a tree can bear is primarily determined by the tree reserve level. Excess fruits drop and this may happen at various stages of fruit development. Fruit drop is governed physiologically by the size of reserve food base in the tree and also by climatic condi tions prevailing during this time. Even if trees have sufficient reserves, lack of K or soil moisture deficits during fruit development phase or pest and disease attacks on flowers and developing fruits may act as limiting factors controlling the size ofthe final crop. Therefore, at this stage trees have to be managed very well providing all necessary inputs correctly.
Mango Tree Management
Mango yields are often very low when grown with out proper tree management. Then the productivity of trees basically depend on variety and climate. Also under such conditions there might be greater fluctuations in yields of a particular variety over s easons solely due to climatic conditions prevailing during the season. However, if a scientifically sound management system is employed, the productivity of trees can be significantly increased while yield fluctuations could be minimized providing the gr ower with an assured supply of a reasonable yield every year, a prerequisite for a profitable mango industry.
The objective here is to examine and explain various issues related to mango tree management for enhancing orchard productivity. A considerable volume of technology is available at the moment with the Department of Agriculture about mango tree management and some other technologies, especially in relation to new varieties, flowering etc. are on the pipeline. Available technology on mango tree management is fairly adequate enough to manage commercial orchards or home garden trees to achieve optimum pr oductivity.
Throughout this discussion of mango tree management, it is attempted to provide explanations to questions on what is mango tree management, why mango trees should be managed and how to manage mango trees.
First thing we have to look at in mango tree management is to see what tree management actually is. Let us fist define what is management before we go further into this subject. When tree management is going to be defined, it is essential for us to kn ow what is an adaptable variety, because the success of tree management at the first place depend on the variety.
Adaptable variety and its compatible environment is the foundation on which tree management systems are built up. An adaptable variety is a one which under specific climatic conditions show close relation to an ideal variety having the characteristics of precocity and regularity of bearing, high productivity, production of attractive and good quality fruits, resistance to serious pests and diseases prevalent in that area and have a dwarf tree habit. Now a tree management system therefore is a scient ifically designed course of action to be followed to surface the potential productivity of the particular adaptable variety to its maximum.
Management system for a commercial orchard begins with the selection of orchard site and the choice of variety or varieties to be planted in the orchard and extends upto day to day activities performed on trees in the established orchard. Therefore, a mango tree management system is specific to a variety, to a location and to the stage of tree growth as well. Another important aspect that should be kept in mind in designing a tree management system is the perennial nature of mangoes. This means that in managing trees, we have to think about the sustainability in production, but not just the productivity in a year or two to maximize profits.
One of the most important things in tree management is the selection of a right variety compatible to the growing environment. When the right variety is in place, tree management would facilitate enhancing the tree productivity and orchard profitabili ty. However, when incompatible varieties are grown in an unmatched environment any tree management system, less than that of growing tunnels with controlled environments, would hardly make any significant improvements in fruit yield. This is a fact that have been well understood by scientists as well as growers in many mango producing countries.
How to Select a Mango Variety
Since the profitability of an orchard depend on the right variety and the performance of a variety is greatly affected by the environment, selection of varieties to be adopted should be done very carefully. For intermediate and dry zones of Sri Lanka, where much of the lands are available for commercial agricultural activities varieties Willard, Karthacollomban and Vellaicollomban are more suitable. When authenticated planting materials are used and appropriate sites for orchards are selected these v arieties may be ideal because under these conditions, varieties mentioned above starts to bear at 3 - 4 years after planting and bear continuously every year. If good cultural management practices are adopted growers can expect reasonable high and profit able yields from these varieties every year.
If growers are interested in going for new varieties, especially exotic varieties which have good market demands, it is advisable to analyze the growing environment of those varieties with that of the local environment where the orchard is going to be established. Since mango is very sensitive to environment, particularly to air temperature, temperature profiles may be helpful to decide the appropriateness of such varieties to local environment.
To illustrate how this could be done, the temperature profiles for Homestead, Florida is given in comparison with temperature profiles at Aralaganwila, Mahawali System B (Fig 1.). If a grower in Aralaganwila is interested in going for variety Haden or Tommy atkins, it is better to find answers to the following questions before desiding to adopt the variety. If this variety is successfully grown in Florida, what effects the low temperatures experienced in Florida during September - February have on th e fruit yield in following season. What will happen to yields if the winter temperatures are higher than the average in a particular season. If you look into the answers for these questions you will get to know that cool temperatures during the period fr om September to February is an essential prerequisite for those varieties to produce good crops in the following summer and above average temperatures during winter will produce more leaf flushes and fruit yields will be lower in the following season. Th en you have to think, what effects the temperatures in Aralaganwila, which are considerably higher than that in Florida, will have on the productivity of these varieties. It should be mentioned here that most of these varieties are very sensitive to temperatures and a little difference as much as 5 oC accumulated over seasons would make a significant difference in tree productivity. Again as another example, if you think of growing Kensington, Australia's major variety, just consult an Australian mango grower and ask what happens to there crop if their winter temperatures in June -July go above average in a particular season. Or if you meet a Thai mango grower who had visited Australia, ask him why they do not grow Kensington in Thailand. If you intell igently analyze these facts you can make wise decisions on adoption of those new varieties. This kind of environmental analysis, not only with temperature but also with rainfall, relative humidity etc., is very helpful in deciding what varieties to grow in a particular area if growers are interested in going for new exotic varieties.
Selection of Orchard Site
The orchard performance and profitability to a greater extent depend on the selection of planting sites. In selecting the site factors like soil type, soil depth, soil fertility, drainage, water table etc. must be carefully studied. Mango is not too p articular as to soil type providing it has good drainage. Mangoes grow in most soils, but for commercial production the poorer, shallow soils are better. On these soils, the trees stay smaller and more manageable. On the other hand, rich deep loam soils certainly contribute to maximum growth, but if the soil is too rich and moist and too well fertilized, the tree will respond vegetatively but will be deficient in flowering and fruiting. Mango perform very well in sand, gravel and even on oolitic limesto nes as in Southern Florida and the Bahamas.
The water table must be well below one to one ant will affect root functioning and ultimately will affect the tree productivity. When trees grow bigger, if water table is high, it will affect flowering and fruit set also because one of the prerequisit es for good flowering is a dormant period of 2-3 months prior to flowering with less water.
If inappropriate sites such as places with high water table and with very rich, fertile, deep moist soils are selected, it will affect the productivity of orchards. Therefore, selection of the site must be very carefully done especially because if som ething is wrong it can not be corrected easily after the orchard is established.
Land Preparation, Irrigation and Drainage Layout
During the stage of land preparation, after felling and clearing the jungles, as the case may be, a rough levelling must be done. Care should be taken not to disturb topsoil too much in places where soil depth is low. The degree to which the land must be cleared and levelled after all depend on the type of irrigation system that is going to be adopted in the orchard.
The irrigation system is one of the most important resources in a commercial orchard. The type of irrigation system may be decided on the capital budget for orchard development. For mango orchards flood, basin, furrow or under tree sprinkler irrigation systems are commonly used. Under tree sprinkler system is the best out of these systems and it is the most expensive system as well. With this system it is possible to enhance the water use efficiency of the orchard by cutting down the water requirements s ignificantly as the conveyance losses are very low compared to other systems. It also has an added advantage that trees can be manipulated with greater efficiency with irrigation, a powerful management tool in commercial orchards, in controlling tree pro ductivity to its optimum.
The principal objective in irrigation is to apply the required amount of water per tree at right time. This quantity of water should be evenly applied around the root zone which is considered to extend 1 - 1.5 m beyond the canopy drip line to a depth of about one to one and a half meters in well grown trees. Irrigation systems should be designed at a capacity to provide the maximum water requirement during peak water demand periods with in the life span of the irrigation system. Water requirements of mango depend on many factors such as soil type, soil depth, rain fall patterns of the region where orchard is established, plant density, variety , tree size and tree age etc. All these factors must be taken into account in designing the irrigation syst ems to increase the water use efficiency and minimize costs of water in case grower has to pay for irrigation water.
Equally important like the irrigation system is the drainage system in the orchard. The objectives in having a drainage system is to remove the excess water from the active root zone during rainy months of the year and to keep the water table in the o rchard as far as possible below the active root zone , that is roughly one to one and a half meters below the ground level. Building up of a persistent water table may damage root growth and the functioning of absorbing roots. High water tables and high soil moisture at some critical periods of production cycle may also affect flowering of trees and subsequent productivity.
However, lands with poor drainage and high water tables may also be utilized for mango cultivation provided that special techniques are followed in land preparation. Under such conditions trees may be planted on raised beds, about 1.5 - 2 meters from the base level which will create a well drained space for trees to have root growth. In this case however, a good irrigation system must also be desinged to water the trees as simple methods such as flood, basin techniques may be difficult to follow. Und er tree sprinkler system may be the best option.
True to type, healthy and vigorous planting materials have a striking effect on the success of the orchard. Planting materials may be purchased form a registered nursery to guarantee the authenticity as to the variety and hygiene of plants. Plants may also be produced by the grower well in advance so that planting materials reach appropriate stage by the time of planting at the orchard. Every care must be taken to procure the bud wood from a reliable source.
Planting should be done when the growth flushes in the plants have hardened. Leaves should be cut to half its size to minimize transpirational water loss and to reduce transplanting shock. It is better to establish plants in the orchard after heavy ra ins are over. In case appropriate drainage and irrigation facilities are available, planting may be done any time of the year. It is advisable to paint the stems of plants with a white water based paint to protect plant stems from direct sunlight and hea t.
Plant spacing may be adjusted depending on soil type, variety and management systems to be adopted. For variety Willard a spacing of 7 x 10 meters is recommended while for Karthacollomban and Vellaicollomban, recommended spacing is 10 x 10 meters. If the soils are sandy or tree dwarfing methods such as regular pruning or use of chemical growth retardants are to be used, high density planting may be done with narrower spacing. However, when spacing is manipulated, it should be kept in mind to use with in raw spacing to adjust plant density. It is always better to have 10 meters of inter raw spacing to facilitate orchard management practices when trees grow bigger.
Planting designs such as rectangular planting, triangular planting etc. may be used. However, rectangular planting designs are commonly used in commercial orchards. Planting holes are made about 2 - 3 months priors to planting and filled with topsoil, compost and basal fertilizer mixture and heap up to allow the soils to establish. In loose soils 60 x 60 x 60 cm planting holes are sufficient while in hard soils 90 x 90 x 90 cm holes are recommended. By the time of transplanting soils must have well compacted in heaped planting holes. Planting should be carried out in such a way that the stock-scion union is about 4 - 6 inches above the ground level. Scion should never touch the ground at all.