CROP HUSBANDRY-VANILLA CULTIVATION PRACTICES IN KERALA

VANILLA (Vanilla planifolia)


Vanilla is a tropical orchid requiring a warm climate with frequent rains, preferring an annual rainfall of 150-300 cm. Uncleared jungle areas are ideal for establishing vanilla plantations. In such locations, it would be necessary to retain the natural shade provided by lofty trees and to leave the soil or the rich humus layer on the top undisturbed. Vanilla is cultivated on varied type of soils from sandy loam to laterites. It requires filtered sun light. In the absence of natural shade, trees should be grown to provide shade.

Preparation of land

Clear the land of jungle growth and prepare for planting. Being a creeper, the plant requires support up to a height of about 130-135 cm. Cuttings of Plumaria alba, Erythrina lithosperma, Jatropha carcas and Glyricidia maculata are suitable as live supports. The growth of live standard is to be adjusted to make them branch at a height of 120-150 cm to facilitate trailing of the vines and artificial hand pollination.

Time and method of planting
Vanilla is propagated by planting shoot cuttings in situ. Plant rooted cuttings of 60 cm length. Longer cuttings bear earlier than shorter cuttings. Rooted cuttings as well as tissue culture derived plants can also be used for planting.

Plant the cutting with the onset of monsoon rains. Set out the cutting at a spacing of 2.7 m between plants and 1.8 m between rows in pits of size 40 x 40 x 40 cm. Trail the vines on the live supports and when they attain a height of 135 cm trail them horizontally on bamboo poles tied to vertical supports or branches of support plants in loops touching the ground.

Manuring
Being a surface rooting plant, manuring should be confined to the surface layer of soil. Provide heavy and frequent mulching to the vines. Apply 120 g of N in the form of leaf mould or FYM in two split doses in June-July and September-October.

Aftercultivation
Vanilla cannot withstand even the slightest root disturbance. Hence remove weeds from the plant base by hand-weeding and use them as mulch.

Being closely planted, no intercrops are raised in a pure plantation of vanilla. But vanilla can be planted as an intercrop in coffee, coconut, arecanut etc.

Pollination, harvesting and curing
Flowering of vine commences usually by about the third year. The inflorescence is produced in the leaf axils. There is a tendency for some of the vines to maintain only vegetative growth. A light nipping off or pruning of the terminal shoots hastens flowering. Due to the peculiar structure of the flowers, self-pollination is impossible. Hence hand pollination is adopted for fruit set. Best time for pollinating the flowers is between 6 a.m. and 1 p.m. and a success of 80-85% can be obtained. Successful fertilization is indicated by the retention of calyx and the stigma even after four days of pollination.

The pods ripen in about 9-11 months time. Before attaining maturity the fruit is dark green in colour and when ripe yellowing commences from the tip of the pod. Collect the pods at this time, as this is the optimum time for harvesting the pod. If allowed to remain on the vine further, the pods split. Free vanillin is not present in the beans when they are harvested. They also do not have the aroma. Vanillin is developed as a result of enzyme action on a glycoside occurring during the process of curing of beans.

Harvested beans are subjected to curing which is characterized by four phases.

1. Killing or wilting beans to arrest the vegetative development in the fresh beans and initiate the enzymatic reactions responsible for the production of aroma and flavour. Killing is indicated by the development of a brown colouration of the bean.
2. Raising temperature of the killed beans (sweating) to promote the desired enzymatic reactions and to achieve rapid drying so as to prevent harmful fermentation.
3. Slow drying at ambient temperature until the beans have reached about one-third of original weight for the development of various fragrant substances.
4. Conditioning the beans by storing them in closed boxes for three months or longer to permit the full development of desired aroma and flavour.

Curing of vanilla involves immersing the beans (2-3 days after harvest) in hot water at a temperature of 63 to 65ºC for three minutes for the cessation of vegetative life. After a rapid drying on woolen blankets, when the beans are still very hot, they are kept in chests lined with blankets. Next day they are spread out in sun on blanket for three to four hours and rolled up to retain the heat. Repeat this for six to eight days during which beans lose their weight, become supple and can be twisted on finger without breaking. This is followed by slow drying in the shade for a period of two to three months.
Properly dried beans are kept in trunks where the fragrance is fully developed. Finally, they are graded according to size and bundled and placed in iron boxes lined with paraffin paper. The vanillin content of properly cured beans will be about 2.5 per cent.

Plant protection

The occurrence of a wilt disease caused by Fusarium oxysporum has been observed. For control of wilt disease adopt the following measures.

1. Remove diseased plants along with surrounding soil where the disease is observed.
2. Remove weeds around the plants.
3. Mulch the base of the vine with dry leaves before and after monsoon.
4. Avoid injury to roots during cultivation.
5. Drench soil around the base of vine with 1% Bordeaux mixture.

Fungal diseases like shoot tip rot, stem and bean rot caused by Phytophthora sp. as well as immature bean drop are noticed. The disease-affected portions are to be removed regularly and 1% Bordeaux mixture should be applied on the affected plants.