Farmers had already proved that the agro-climatic conditions of India can be turned favourable for the cultivation of Rambutan, one of the most popular fruits of Southeast Asia. Kerala, Tamil Nadu, Mangalore, Kudak regions of Karnataka, Konkan region of Maharashtra are suitable for rambutan cultivation. We can grow rambutan as an ornamental tree in our garden. The edible inner portion enveloping the seed is juicy and sweet. The fruits are rich in carbohydrates, vitamins, calcium, magnesium and potassium. Studies show that the antioxidants present in the rind as well as in the aril part of rambutan neutralizes the growth of cancer cells.  

Favourable climate & soil

Rambutan grows well in warm tropical climate. Higher humidity and favourable climatic condition are important factors. It also requires a minimum of 150 cm well distributed annual rainfall. The trees grow well at elevations up to 800 m above sea level. The ideal temperature for optimum growth is 22 to 35° C. But the slight climatic variations would not affect its yield and growth.  Well drained loamy soils with good organic content are most suitable for optimum growth and yield. Acidic and alkaline nature of the soil should be moderate (pH value 4.5 to 6.5). Sites prone to waterlogging should be avoided for plantation. Orchards in slightly sloped lands yield better, because they capture maximum sunlight.

Popular Varieties

Several commercial, as well as homestead varieties of Rambutan, are available. Varieties such as N18, HG Malwana, HG School Boy, HG Baling, HG Rongrien and HG Jarum Emas are excellent for commercial planting while E35 and King are homestead varieties. N18 and E35 varieties are developed by Kottayam based Home grown Biotech. Besides, Homegrown have also identified and introduced several commercial as well as homestead varieties of rambutan in Kerala, which are popular in Thailand, Srilanka and Malaysia.

Rambutan E35

 

Propagation

The Rambutan, a plant of the Sapindaceae family, is known by its scientific name Nephelium leppaceum. The name ‘rambutan’ originated from Malay word ‘rambut’ meaning “hair”. The fruit is round or oval in shape. Usually a cluster contains five to twenty fruits. Leathery outer cover often looks red or yellow in colour.

 

Seedling propagations are not used in rambutan culture because of the difference in sex type of flowers. Instead, budding is the right method of producing high quality plants. If nurtured well, it starts flowering after three years and yields optimum production after six to eight years.   

  • The ideal spacing in between two saplings is 40 ft, which can vary from place to place depending upon the weather condition.

  • In one acre of land, up to 35 saplings could be planted.

  • The pits (1m sq.) should be filled with topsoil mixed with 3 pots of well decomposed cow-dung manure or compost and 1 kg each of rock phosphate. Then place the plant with the bud union above the soil level.

  • A handful of compost or dried cow-dung manure and rock phosphate mixed with soil should be sprinkled around the planting hole. Additional fertilizers can be given after 6 months, but only after the new flush of leaves are emerged and matured.

  • Proper irrigation is essential during the dry season. Keep the orchard clean by periodic removal of weeds. Dried branches and water suckers should be removed regularly.

 

Since rambutan tends to have long, upright growth, early pruning is recommended. When the budding attains 4 ft, trim the main stem at 2.5 ft. When new sprouts emerge, allow 3 or 4 limbs in different directions, and these limbs produce primary, secondary and tertiary branches, giving the tree a semi-elliptic shape. This will help to attain optimum yield. We can complete this planting method by two years.

Fertilizer Application

Rambutan is a plant favourably responding to fertilizer application. Fertilizers could be given only after the new flush of leaves are emerged and matured. Adding 5 kg of compost or cow dung manure mixed with soil is effective. Mulching is found to be very effective in moisture conservation. Spraying ‘jeevamritham’ could stimulate the growth of useful microorganisms. It will also help the plants to overcome drought. Application of cow dung manure enriching Trichoderma is useful.

 

  • Applying 100 g of NPK 18 complex three times in a year (pre monsoon, onset of monsoon and during summer rain) is found effective in stimulating growth.

  • For growing trees (six years and above), a fertilizer rate of 1 kg of NPK complex, 30 kg cow dung powder or compost should be given.

  • Fertilizer application can be started after cutting off the branches followed by harvesting.

  • Nitrogenous fertilizers should be applied only in August- September.

  • Applying 300g to 1kg of potash before the time of flowering is effective. If same amount of potash is added one month before harvest, it will also give high quality fruits.  

Pollination

Flowering season is from February to April. The proper method of irrigation is needed according to the age and yield of trees. Rambutan is a cross pollinated crop hence the presence of honey bee is essential for its fruit formation.It takes three weeks after pollination for the initial stage of fruit formation. Again after three weeks we can adopt innovative methods for protecting its quality. Apply 25gm Boron (for small trees) and 50 gm (for big trees) mixed with soil at the time of flowering. Application of Pseudomonas fluorescens liquid formulation (6ml/l) is also worthwhile in managing fruit drop and production of quality fruits. For fruiting trees, in addition to 200 g of 18 complex, 100 to 250g of muriate of potash can be given to 4-5g/l of sulphate of potash can be given as Foliar (1lt per tree). Spraying 1g/l wettable sulphur to the developing fruits is very effective in reducing fruit drop. Fruit drop can be caused by several reasons like micro element deficiency and oxin- cytokinin hormone variations. Giving foliar spray by detecting the right proportion of micro elements through leaf tissue analysis is effective. Spraying sulphur solution (3g/l) is an effective method for preventing any type of fungus attack.

 High-quality trees cultivating in the orchards contain two types of flowers. Functionally 95 percent of these flowers are female and bisexual in structure. In order to increase the productivity, the pattern of certain bisexual flowers that perform the female functions has to be altered to that of male, which in turn accelerates the productivity. For this process, 10 percent cluster of flowers has to be identified and marked. Out of this selected cluster, some buds open at the same time the rest remains as buds. That period is the apt time to spray Superfix solution. In two litres of water, one ml of Superfix has to be mixed and sprinkled before 9a.m. After 6 days flowers might have transformed to male flowers and stamen bursts out, this period facilitates increased productivity. In order to obtain quality fruits utmost attention has to be given for such vital process. 

Pest Control

Usually, pests would not affect well nurtured rambutan trees. Maintaining 40 ft spacing is a good method of plant protection. Drying up of branches, attack of mealybugs, beetles and leaf eating caterpillars are the major threats to plants. Burning the affected branches is an effective way to avoid further spread. In case of severe attack Neem-based formulations can be used to control leaf-eating caterpillars. Verticillium is effective in managing mealybug infestation.

 

Dr. Sunny George

Director, Research & Development

Homegrown Biotech

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