(Aquilaria agallocha Roxb.)
Agar oil and agaru or agarwood are the most exalted perfumery raw material obtained from the infected wood of agar tree. This transformed wood due to fungal infection yields agar oil on distillation that has unique fragrance and high export value. The agar oil known in the East as Agar-attar is one of the perfumery’s oldest materials. It is considered one of the costliest perfumery raw materials used in high-class perfumery and as a fixative, imparting a lasting balsamic odour to the product. Its traditional use in India, Middle Eastern and Far Eastern perfumery, both as skin daub and as a fixative, rivals its former usage holy incense by the Hebrews.
Agar tree (Aquilaria agallocha) is distributed in all the Northeastern States and widely cultivated. It is now rarely found in wild state.
Variation within species
In Assam two types of A. agallocha could be identified as ‘Jati Sanchi’ and ‘Bhola sanchi in the population. ‘Bhola sanchi’ is comparatively of quick growing but yield is less than that of Jati sanchi. It is the Jati sanchi that is preferred for commercial cultivation.
Soil and Climate
Agar plant prefers high humid, sub-tropical climate with rainfall 1800-3500 mm per annum. It grows from sea level upto 500-m altitudes. It is a sun-loving plant and requires lot of sunshine.
It prefers well-drained deep sandy loam-to-loam rich in organic matter but can profitably be grown in marginal soils and also in shallow soils over rocky beds with cracks and crevices. It grows well in hill slopes and forest environment. The traditional agar growing areas show that it prefers acidic soil reaction.The mycorrhiza and other beneficial fungi which seems to be responsible for oil formation in the agar tree being soil borne requires acid soil for their population build up.
Agar is a long-term plantation crop. A profitable plantation may be of 12 years cycle or more. The Short cycle plantation yields only essential oil or ‘agar attar’ of low quality (Boya oil). The plantation may be planned in two ways:
(a) Planting at wider spacing along with some suitable intercrops and harvesting at the end of the crop cycle.
(b) Planting at comparatively closure spacing and harvested at 2-3 phases. In the second approach about 8-10 years of planting about 40 % selected trees may be harvested with a view to thin out the plantation for better growth and development of the remaining trees and also to get a substantial income.
Planting should be done when the plants have the greatest chances of survival. The best time is during the rainy season (May-September).
Agar in tea garden
Under average condition spacing ranges between 2.5-5 m, (initially accommodating about 1700 plants per hectare) which at later stages i.e., after 8-10 years of growth maintained at 4-5 m by harvesting in phase manner. When the planting is raised with some other forest species the spacing may be given accordingly. The distance for avenues and public places depends upon the situations and purpose of planting which may range between 3-4 m.
Planting of the saplings is done in well-prepared pits of size 50 x 50 x 50 cm made in advance and preferably in the evening time or during the cloudy weather. After planting staking should be done to keep the seedling in upright position and the soil around the plant should be firmly consolidated. Immediately after the planting, watering is necessary (if no rains).
In no case, the soil around the root be disturbed or removed during planting. In the open and in public places the newly planted seedlings are to be protected in cages till they grow fairly large. For better and faster growth of the plant, the pits should be weeded and hoed to keep the soil loose and free from weeds.
Agar in Agro-forestry
Agar tree is suitable for growing on field boundaries and for dividing whole plot into sub-plots. Not only this, agar tree is also grown on borders of gardens, school compounds, office compounds, parks and residential sites. The good capacity for pollarding and coppicing has made it suitable to fit in agro-forestry. The canopy of Agar tree is such that it allows sunshine penetration partly. Thus, it can be planted in field boundaries, bunds etc., without affecting the field crops.
Besides, agar tree has been successfully grown for strip planting along banks of ponds, tanks, canals and roads. In hilly areas / tillas as in Barak valley it can be planted on poor soils on hill slopes, tilla tops. They help in reducing soil erosion and land sliding caused by rushing water during rainy season.
Agar tree could successfully be introduced in Social Forestry and also in afforestation programme.
Agar in Tea / Coffee garden
Tea growing situation is also ideal for agar tree. The increasing demand of agarwood, it is being introducing as shade tree in tea plantation particularly in Upper Assam with success. Agar tree is evergreen and with spreading canopy it allows partial penetration of sunshine through it. Regular looping of branches above tea bushes is necessary.
Soil working to a radius of 50 cm is to be done once in 3-4 months. Fertilizer application should also be followed by these operations preferably twice in a year, before and after monsoon from second year onwards.
Agar seedlings are foraged by goats or cattle. To protect plantation, fencing is necessary. Initial 4-5 years period should be protected from farm animals. Trenching around the plantation has also given good success. All the replacements of casualties should be done in the same planting season and if necessary second replacement may be done during the second year using large size seedlings.
Vegetables/pulses or aromatic crops like Patchouli (Pogostemon cablin), Sugandhmantri may be cultivated as short season/short term intercrops during first three to five years of plantation. In the later stages shade loving medicinal plants like Sarpagandha (Rouvolfia serpentina), long pepper (Piper longum) may also be grown for another few years depending on plant population and land type. Ginger/Turmeric may also be planted leaving about 50 cm around plant base. Both the crops are exhaustive in nature for which some special care has to be taken. This type of crops should not be taken more than two seasons.
It is not necessary to apply inorganic fertilizers at the time of planting. Fertilizers should be applied after complete establishment and only from second year of planting.
Well-decomposed cow dung/FYM @ 5 -10 kg/pit of size 50 cm3 may be applied in pit and well mixed with soil prior to planting. Un-decomposed FYM or fresh cow dung should not be applied in any case. The rhizosphere of Agar tree (0 - 45 cm) exhibits a higher rate of microbial population when organic manures are used.
N, P2O5 and K2O at 10: 10: 4 ratios as per the following schedule may be applied from second year onward preferably in two splits-
Second year …… 200 g/ tree
Third year ……. 300 g/ tree
Fourth year onward. 500 g/ tree
The fertilizers should be applied along with decomposed cow dung / compost @10 -15 kg/ tree. In the virgin forestland initially no fertilization is required. Later depending on crop growth fertilization may be resumed accordingly. From 6-7 years of growth nitrogenous fertilizer @ 400-500 g/ tree per year may be applied in two splits during pre and post monsoon period. This may help in keeping the tree wood soft, with higher content of cell sap enabling easy insect boring followed by fungal infection and spread of infected area over a larger wood volume ie, higher rate of bioconversion.
To be continued................