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| Sunday, 4 August 2002 |
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Features |  |
| News Business Features Editorial
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Jak is an important crop
by Prof. H. M. P. Gunasena Faculty of Agriculture, University of Peradeniya
The jak is one of the most widely grown fruit crops in the tropical lowland. It is an important fruit crop in India, Burma, Sri Lanka, Malaysia, Indonesia, Thailand, the Philippines, Vietnam and many other tropical countries of the world. People of these countries not only eat the jak fruit but also export it in various forms such as dried or fried flakes and canned. A good demand exists for these traditional jak products in the western countries where different ethnic groups live. It can supply even a global demand, being the world's famous and the largest edible fruit weighing as much as 50 kilograms. Jak is an important tree for the people of Sri Lanka and it influences many aspects of our life. Mention of jak has been made in the Mahawansa as early as the fourth century BC. In early literature, Amawatura, Vissudhimargaya and Yogaratnakaraya refer to jak as an important food crop. In fact in the past the traditional plate of rice the villagers constituted one half of rice and the other half boiled jak. The jak fruits are so in plenty in the season that they could meet this demand. In the 17th century Robert Knox wrote that the fruit is a great help to the people and form greater part of their food". The traditional uses of jak has been gradually lost due to introduction of wheat flour and other refined foods. A resurgence in growing and use of jak has begun recently probably due to the escalating cost of living due to the high prices of rice, vegetables and other consumer goods. Jak fruit has many other uses than food, in fact no apart of the jak tree is without some value. Where to grow jak Jak could be grown in most parts of the country, except at very high elevations. When grown in very high elevations, above 1000m, fruiting is poor due to slow tree growth. Highest population of jak trees are found in the Kandy, Kurunegala, Kegalle, Badulla and Matale districts but it also grows in all districts including northern and other dry zone areas. It is an ideal home garden tree and for mixed forest plantations and agro forestry systems. How to select varieties There are two main types of jak, namely "wela" in which the flesh is soft when ripe. The other type "Waraka" is superior to wela as the flakes are hard and crisp when ripe. The waraka varieties are preferred by the growers. The Department of Agriculture has selected some superior waraka varieties, namely, Father Long and Rosa Kos. Father Long bears throughout the year producing fruits weighting 7 - 9 kg. and the flesh is firm and yellow. The fruits of Rosa Kos are similar, but the flesh is light pink when cooked. Johore jak or Singapore jak is another variety, bearing in about 5 - 6 years. This was popular during the jak planting campaign of Mr. Arthur V. Dias in the 1930s. Another variety is Kuru kos which bears small fruits which is of less commercial significance. The selection of varieties depends on the purpose of growing jak. Most often the selection is based on fruit quality, hence waraka types are used. They are dual purpose and can be used for timber as well. For home garden planting the best are the budded varieties as they do not grow to a great height, they are dwarf and spread well with a large tree diameter and bear early. The budded trees are not good for timber production as the main trunk branches at a lower height and not long as in a normal tree. Jak is commonly propagated from seeds as it is the cheapest, easiest and most convenient method. However, plants grown from seeds exhibit a high degree of variability due to cross pollination and not be true to type. When propagating with seeds large and heavy seeds should be collected from selected mother trees. Only large seeds from fruits should be selected for planting because large heavy seeds have more stored good, hence higher germination. They also retain their viability longer, sprout earlier and produce healthier seedlings than small, light seeds. Seeds should be sown immediately after extraction from the fruit and they should be placed in most coir dust sawdust, if short term storage is needed. In any case the cotyledons should not to be allowed to dry. These seeds should be washed in water to remove the slimy coating. When seeds are soaked in water for 24 hours before sowing, germination is quicker and for best results the seeds should be sown soon after extraction. Generally seeds are sown in polythene bags of size 6 x 9 inches. The bags are filled with a mixture of top soil, sand and compost at the ratio of 2:1:1. The compost will make the soil friable and fertile. Seeds could also be sown in coconut husks filled with soil to cover the seed. These could be directly planted in the field with the husk after germination. Sometimes the seeds are sown in nursery bed and transferred into polythene bags. This is a troublesome procedure as it involves two operations. Only one seed should be sown per bag. The seeds cannot be stored for a long time as they lose viability. Sensitive Jak seedlings have a long taproot system which is very sensitive to injury and thus do not withstand transplanting well. For this reason it is advisable to sow the seeds in individual containers or directly in the field. If seeds are to be started first in seed beds, the seedlings should be transferred to individual containers before food reserve in the cotyledons is exhausted. Otherwise there is a poor chance that they will recover from the shock of transplanting. The seeds will take few days to germinate and within 3-4 weeks germination will be complete. The bags should be kept in the shade and watered daily and kept weed free. When the seedlings have reached a height of about 3-5 inches, see whether the roots have penetrated the bags, if so trim the roots with a sharp knife or a pair of secateurs. Seedlings should be maintained for 10-12 weeks before transplanting in the field. Jak could also be propagated vegetatively to take advantage of the superior trees. Superior or Plus trees are those with good characteristics such as desirable tree form, high yielding, regular and early bearing and fruits of good quality. The number of fruits per tree, their size, length and thickness of flakes and sweetness and flavour are also important characteristics of superior trees. These trees should be carefully selected from the available populations for improvement of the species. Waraka type of trees with the above characteristics are locally available and should be identified for removing budwood for propagation. Vegetative propagation will produce true to type seedlings and this is an important when outstanding varieties have to be perpetuated. Budding, grafting, particularly approach grafting and air layering are common methods of propagating jak. Inarching is also suitable of small scale jak propagation. Patch budding is the method commercially used in propagating jak. This method gives the best result of the different budding techniques. Budding may be done at any time in the year as long as the stocks are kept in active growth. Best rootstocks are 8 to 11 month old seedlings which are produced from ordinary seeds to penetrate through the container. If this happens the root will have to cut during transplanting in the field. This should be additional injury to the plant. Continued next week.... |
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