Cultivation. Valuable statements concerning the citronella oil industry are contained in a paper by B. Samaraweera3) which was read by A. Jayasuriya at a meeting of the Agricultural Society of Ceylon. The maha pengiri grass (comp. p. 217) affords a good yield of oil rich in aromatic substances. However, it demands a rich soil, much care, and must be transplanted frequently. The lena batu affords a smaller yield of less aromatic oil, but flourishes on poorer soil and requires no transplanting. Inasmuch as the bulk of the Ceylon oil is obtained from lenabatu, this explains why the Ceylon citronella oil possesses less commercial value than the Java and Singapore citronella oils. A change in this respect can be brought about only when maha pengiri is cultivated in Ceylon.
1) Loc. cit.
2) Comp. also Bull. Imp. Inst. 10 (1912), 299.
3) Oil, Paint and Drug Reporter 70 (1906), 25. - The Times of Ceylon April 3rd 1906; Report of Schimmel & Co. October 1906, 16; April 1907, 27.
Fig. 26. A Field of Maha Pengiri-Grass in Ceylon.
Care should be exercised not to set the plants too close; about 15000 plants per acre1). The soil should be well drained and fertilized, and more attention should be paid to the removal of weeds. Because of the difficulty of obtaining cheap labor during the rice harvest, citronella plantations are in danger of being ruined entirely or in part. Hence farmers are advised to introduce mowing machines for the purpose of reducing the cost of production. The freshly cut grass, however, is not used for distillation, for it yields an oil with an unpleasant odor; but the well dried grass which yields an oil with an agreeable odor. During the process of drying, fermentation and decay must be carefully avoided. Four or only three cuts are made annually on the plantations. The latter practice is preferable. The yield of oil increases up to the third year and averages about 71 lbs. 3 oz. annually per acre. After the third year the yield of oil decreases continuously although the appearance of the grass is very good.
The meteorological conditions exert a great influence on the citronella grass. Moderate altitudes afford a good oil and a larger yield than the same grass affords at higher altitudes.
In Ceylon the cultivation of the grass is carried on exclusively in the Southern Province2), more particularly in the region between the Gin Ganga to the Northwest and the Walawi Ganga to the East. The grass is cultivated on the slopes of the hills. The individual tufts of grass grow, at irregular intervals, to a height of 1 m. According to reliable dealers, somewhat between 40000 and 50000 acres are cultivated with citronella grass.
Provided the formation of seeds is prevented by regular harvests, the plants demand little or no care. If not harvested regularly, the tufts grow too dense, become yellow within and decay. Generally two periods for harvest are distinguished. The first and principal season occurs in the months of July and August, the second during the months of December to February. The yield per acre for the summer campaign is estimated at from 16 to 20 bottles (of 22 oz.) per acre and from 5 to 10 bottles for the winter campaign. Exact statements cannot be made since the yield naturally depends on the weather, on the age of the plants, and the location of the plantation. Thus e. g. even favorable conditions of weather and soil will not prevent the diminution of the oil output with the advance of age. When a field has reached the age of 15 years, a replanting is necessary if it is to be worked profitably.
1) 1 acre = 40,467 Are.
2) Comp. Bericht von Schimmel & Co. October 1889, 11.
Fig. 27. Citronella Oil Distillery Plant in Ceylon.
Production. The distilleries are mostly located at the foot of a chain of hills where an abundance of water of low temperature may be had.
As becomes apparent from the description which follows, the construction is by no means primitive. Indeed it is remarkable to note the advancement achieved by the natives, for such are the majority of distillers. Under a long roof that affords protection against the sun there is mounted, on a solid foundation, a boiler provided with safety valve and water gauge. Beside it, on a slight elevation, are placed two iron, cylindrical stills, 6 to 7 ft. high and 3 to 4 ft. in diameter with a common interchangeable helmet. Next to these is the condenser, consisting of a wooden vat and resting on a water basin, sunk into the earth, which accommodates the coil. The container which acts as receiver is still lower in a cellar and kept under lock and key. The entire outfit is illustrated by the accompanying plans (figs. 28 and 29, p. 223).
The method of distillation is that of direct steam distillation without the addition of water. The warm water of the upper condenser is used to feed the boiler, whereas the subterranean basin, through which the coil also makes several turns, serves to effect complete condensation. It is noteworthy that the unseparated distillate as it leaves the condenser is collected in the container behind lock and key. Within certain intervals the owner visits his several plants to skim the oil. The aqueous distillate is allowed to run off whenever the capacity of the receiver demands it.
Dried grass only is distilled. One charge requires about 6 hours to be exhausted.