CROP HUSBANDRY-CLOVE CULTIVATION PRACTICES IN KERALA

CLOVE (Syzygium aromaticum)


Clove requires a warm humid tropical climate with an annual rainfall from 150-250 cm. It grows well from mean sea level up to an altitude of 800-900 m. Deep loam soils with high humus content and black loams of semi-forest regions with good drainage are suited for the cultivation of the crop.

Selection of site
Select partially shaded sites having adequate protection from high winds. Avoid exposed and shady locations.

Seeds and sowing
Clove is propagated through seeds obtained from fully developed fruits known as mother of clove. Collect fully developed fruits from regular bearing mother trees. Dehusk the fruits immediately after collection by soaking in water and peeling. Prepare raised nursery beds with fertile soil rich in humus under the shade of trees. Sow the seeds flat at a depth 2-5 cm and a spacing of 12-15 cm. Water the beds regularly. Seedlings can either be retained in the nursery till they attain a height of 25-30 cm when they are ready for transplanting or potted when they are six months old and transplanted after another 12-18 months.

Planting
Select 18 month old seedlings for planting. Prepare pits of size 60 x 60 x 60 cm at a spacing of 6 x 6 m about a month in advance of planting. Allow to weather. Fill up the pits with mixture of burnt earth, compost and topsoil. Plant the seedlings during the rainy season, May-June or August-September. Provide shade and irrigation during breaks in the monsoon and summer. Banana or glyricidia may be planted to provide shade.

Clove is generally grown as a mixed crop with coffee, coconut, arecanut etc.

Manuring

Apply cattle manure or compost at the rate of 15 kg / tree / annum during May-June.

The recommended fertilizer dose is N:P2O5: K2O @ 20:18:50 g/plant during the first year and N:P2O5:K2O @ 40:36:100 g/plant during the second year. Increase gradually the N:P2O5:K2O dose to 300:250:750 g/plant/year for a well grown tree of 15 years or more. Apply organic manures in May-June with the commencement of southwest monsoon. Apply fertilizers in two equal split doses in May-June along with the organic manures and in September-October in shallow trenches dug around the plant about 1 to 1.25 m away from the base.

Aftercultivation
Conduct weeding and intercultivation whenever necessary. Cut and remove dead and diseased branches of full-grown trees to prevent over crowding. Spray 1% Bordeaux mixture to control dieback.

Harvesting and curing
The trees begin to yield from 7-8 years after planting. The stage of harvest of flower buds determines the quality of the final dried product. Buds are harvested when the base of calyx has turned from green to pink in colour. If allowed to develop beyond this stage, the buds open, petals drop and an inferior quality spice is obtained on drying.

Prior to drying, buds are removed from the stem by holding the cluster in one hand and pressing it against the palm of the other with a slight twisting movement. The clove buds and stems are piled separately for drying. Buds may be sorted to remove over-ripe cloves and fallen flowers. Drying should be done immediately after the buds are separated from the clusters. If left too long in heaps, they ferment and the dried spice has a whitish shriveled appearance (khoker clove).

The traditional method of drying is by exposing them to sun in mats. The green buds are spread out in a thin layer on the drying floor and are raked from time to time to ensure the development of a uniform colour and to prevent mould formation. In sunny weather, drying is completed in 4-5 days giving a bright coloured dried spice of attractive appearance. During drying, clove loses about two-third of its original fresh green weight. When properly dried, it will turn bright brown and does not bend when pressed. The dried cloves are sorted to remove mother of cloves and khoker cloves, bagged and stored in a dry place. The stem after separation of buds is dried in a similar manner as the spice, without allowing mould formation and fermentation.

Clove bud oil
The essential oil is obtained by steam distillation of comminuted buds or whole cloves. On distillation, about 17 per cent essential oil is obtained which is a colourless or yellow liquid possessing odour and flavour characteristic of the spice. Finest oil contains 85-89 per cent eugenol. Clove bud oil is used for flavouring food and in perfumery.

Clove stem oil
Clove stem oil is obtained from dried peduncles and stem of clove buds (5-7%) on steam distillation. The eugenol content of the oil ranges from 90-95 per cent. This oil possesses a coarser and woodier odour than bud oil.

Clove leaf oil
Clove leaves on distillation yield 2-3 per cent oil as a dark brown liquid with a harsh woody odour. When rectified, it turns pale yellow and smells sweeter with a eugenol content of 80 to 85 per cent.

Oleoresin
Clove oleoresin may be prepared by cold or hot extraction of crushed spices using organic solvents like acetone giving a recovery of 18-22 per cent. The oleoresin is chiefly used in perfumery and when used for flavouring it is dispersed on salt, flour etc.

Plant protection

Pests
Infestation of shoot borer Sinoxylon sp. on tender shoots of young plants can be prevented by prophylactic application of carbaryl 0.15%. Prune off the laterals of old trees showing dieback symptoms. Do not allow dried glyricidia and other twigs to remain in the plantation, to ensure that the beetles will not multiply on these materials and subsequently initiate infestation in cloves.

Diseases

Leaf spot, twig blight and flower bud shedding (Colletotrichum gloeosporioides)

Three types of symptoms are seen viz., leaf spot, twig blight and flower bud shedding. On the leaves, necrotic spots of variable sizes and shapes are noticed. Severely affected leaves wither, drop and dry up. In the nursery seedlings, dieback symptoms are seen. Extension of the symptoms from the leaves through petioles results in the infection of twigs. The affected branches stand without leaves or only with young leaves at the tips. The flower buds are attacked by spread of infection from the twigs. Shedding of flower buds occurs during periods of heavy and continuous rainfall.

Control

Spraying 1% Bordeaux mixture at 1-1.5 month intervals reduces disease intensity, defoliation and flower bud shedding. The spraying has to be commenced just prior to flower bud formation and continued till the harvest of flower buds for effective control. Destruction of the weed Clerodendron from the clove garden is recommended to reduce the disease since the pathogen survives on this weed during adverse conditions.

The other diseases of clove are:
Grey blight of clove (Pestalotia palmarum)
Leaf spot of clove (Cylindrocladium quinqueseptatum)
Leaf spot of clove (Alternaria citri)
Sooty mould of clove (Phragmocapnius sp.)
Algal leaf spot of clove (Cephaleuros sp.)
Little leaf of clove (suspected to be due to phytoplasma).