Climate

Lemongrass prefers warm climate with a well-distributed rainfall and well-drained soil. Usually it is grown on poor, gravelly soils. Lemongrass is a perennial grass mainly cultivated on hill slopes as a rainfed crop. The crop provides maximum yield from the second to fourth year of planting and economic yield up to the sixth year. Thereafter, the yield declines considerably. The leaves yield an aromatic oil, containing 70-90% citral. This oil is used in soaps, cosmetics and disinfectants and is a raw material for manufacturing ionones and vitamin A.

The crop is propagated mostly through seeds. It can also be propagated vegetatively through planting of slips.

OD-19 is the improved variety of lemongrass recommended for cultivation.

Seeds can be sown directly in the field or seedlings are raised in a nursery and then transplanted. Transplanted crop is found superior to direct-sown crop in respect of grass yield, oil content and citral content in oil. Seeds are sown in well prepared nursery beds during April-May with the onset of pre-monsoon rains and covered with thin layer of soil. The seed rate is 3 to 4 kg/ha. Seeds collected in the season should be sown latest by August of the same year. The seedlings will be ready for transplanting in 2 to 2.5 months.

The land is prepared by digging. Raised beds of 75-80 cm width and of convenient length are formed with a spacing of 30-35 cm between beds. On sloppy terrain, the beds are formed along the contours. At the early southwest monsoon (June-July), two or three seedlings or slips per hill are transplanted on the beds at a spacing of 15-20 cm in 4-5 rows. Before planting, the top leafy portion of the seedling is cut off leaving the plant stalk about 15-20 cm length.

Rate of manure

Application of compost made of spent lemongrass (refuse obtained after distillation) and wood-ash at the rate of 2500 kg/ha and 1875 kg/ha respectively is found beneficial. Application of nitrogenous fertilizers @ 100 kg/ha in four splits (each after 1st to 4th harvest) has been found to increase oil yield considerably

Harvesting is done by cutting the grass 10 cm above ground level. During the first year of planting, three cuttings are obtained and subsequently five to six cuttings per year are taken subject to weather conditions. The harvesting season begins in May and continues till the end of January. The first harvest is taken about 90 days after planting and subsequent harvests at intervals of 40-50 days. The optimum interval between harvests to obtain maximum quantity of oil is 40-45 days for local types of lemon grass. For OD-19, the optimum interval was found to be 60-65 days when grown in hill-tops and 45-55 days in valleys and lower areas.

Time of seed collection

The crop for seed production is left without cutting to get maximum seeds. The crop flowers during November-December and the seeds are collected during January-February. The whole panicle is cut and dried for one or two days and then threshed and sieved to collect the seeds.

Lemongrass is distilled in copper stills of about 100 kg capacity by steam distillation, or water and steam distillation process. Time required for one distillation is about two hours including the time required for charging and discharging, provided the firewood is well dried and of good quality. For one distillation, about 40 kg of firewood is required. A light yellow, lemon-scented volatile oil is obtained. Providing a perforated disc just above the water level in the copper still will be helpful to produce oil of better quality. This method is known as water and steam method. When crop area is large enough, steam method is found to be more economical. Coal is used as fuel.

The cut grass is chopped into smaller pieces before feeding to the distillation unit. It can be stored up to 3 days under shade without any adverse effect on yield or quality of oil.

Lemongrass oil can be stored up to 3 years without affecting the quality of oil, if kept in aluminum containers sealed air-tight using wax. The containers are to be kept in darkness.

The grass yield during the first year will be about 10 t/ha, which gives about 28 kg of oil. From the second year onwards, the grass yield will be about 25 t/ha giving about 75 kg of oil. The average recovery of oil is 0.30-0.35% with 70% citral for local types of lemongrass while OD-19 variety gives 0.40-0.45% oil recovery and 85-90% citral content.