Mango yields are often very low when grown without proper tree management. Then the productivity of trees basically depends on variety and climate. Also under such conditions, there might be greater fluctuations in yields of a particular variety over seasons 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 grower 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 in the pipeline. Available technology on mango tree management is fairly adequate enough to manage commercial orchards or home garden trees to achieve optimum productivity.
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.
The first thing we have to look at in mango tree management is to see what tree management actually is. Let us first 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 know what is an adaptable variety, because the success of tree management at the first place depends 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 a 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 scientifically 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 up to 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 with the growing environment. When the right variety is in place, tree management would facilitate enhancing the tree productivity and orchard profitability. 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 has 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 depends 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 varieties 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 profitable 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 the environment, particularly to air temperature, temperature profiles may be helpful to decide the appropriateness of such varieties to a 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 deciding 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 the 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 to these questions you will get to know those cool temperatures during the period from 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. Then you have to think, what affects 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 different as much as 5 degrees C 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 intelligently 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 particular 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 vegetative but will be deficient in flowering and fruiting. Mango performs very well in sand, gravel and even on oolitic limestone as in Southern Florida and the Bahamas.
The water table must be well below one to one and will affect root functioning and ultimately will affect the tree productivity. When trees grow bigger, if the water table is high, it will affect flowering and fruit set also because one of the prerequisites for good flowering is a dormant period of 2-3 months prior to flowering with less water.
If inappropriate sites such as places with the 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 something 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 leveling 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 leveled after all depends 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, and 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 significantly 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 ductility to its optimum.
The principal objective of 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 within the lifespan of the irrigation system. Water requirements of mango depend on many factors such as soil type, soil depth, rainfall 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 systems to increase the water use efficiency and minimize costs of water in case grower has to pay for irrigation water.
Equally important to the irrigation system is the drainage system in the orchard. The objectives in having a drainage system are to remove the excess water from the active root zone during rainy months of the year and to keep the water table in the orchard 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 designed to water the trees as simple methods such as flood, basin techniques may be difficult to follow. Under 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 transpiration water loss and to reduce transplanting shock. It is better to establish plants in the orchard after heavy rains 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 heat.
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.