Monday, February 11, 2013

Lemon grass (Cymbopogan flexuosus, family: Poaceae)


Lemon Grass


Lemon grass (Cymbopogan flexuosus, family: Poaceae) is an aromatic plant which grows in many parts of tropical and sub-tropical South East Asia and Africa. Most of the species of lemon grass are native to South Asia, South-East Asia and Australia. C. flexuosus also known as East Indian lemon grass or Malabar or Cochin grass, has its origin in Indo-Burma region and is native to India , Sri Lanka, Burma and Thailand. A related species is C. citratus called the West Indian lemon grass which has its origin in the Malaysian region. Both the species are today cultivated throughout tropical Asia.
In India, the crop is under commercial cultivation along Western Ghats (Maharashtra, Kerala), Karnataka and Tamil Nadu, UP, Assam and foothills of Arunachal Pradesh and Sikkim.

Botanical Description

Lemon grass is a tall, perennial hedge throwing up dense fascicles of leaves from a short rhizome. Leaves are long, glaucous, green, linear, tapering upwards and along the margins; ligule very short; sheaths terete, those of the barren shoots widened and tightly clasping at the base, others narrow and separating. It is a short day plant and flowers profusely in South India. The inflorescence is a long spike about one meter in length. Flower panicles are 30 to over 60 cm long.

Economic Importance

Lemon grass oil is distilled from leaves and flowering tops of Lemon grass. The oil has strong lemon-like odour, due to high percentage ( over 75%) of citral in the oil, which is used as a basic raw material for synthesis of ß-ionones used for synthesis of a number of useful aromatic compounds and Vitamin - A. Lemon grass oil is thus used as a main substitute for ‘ Cod liver oil’. Citral itself is used in perfumery for various grades of soaps, detergents, cosmetics, insect repellents, room freshners, ayurvedic preparations and flavour agent for soft drinks.

Market Potential & Exports

During early fifties, India produced over 1800 MT/annum of lemon grass oil and held monopoly both in production and world trade. This situation no longer exists as Guatemala, China, Mexico, Bangladesh etc. have developed its cultivation over large areas. Currently the world production of Lemon grass oil is around 1300 MT/ annum. However, another 600 MT of a substitute oil viz., Litsea cubeba (rich in citral) is exported by China which limits the scope for any faster growth in export trade of lemon grass oil. Synthetic citral is also available which competes with this oil and natural citral in the market. Cochin and Mumbai are the major trading centres for lemon grass oils. The essential oil of lemon grass from India is being exported to West Europe, U.S.A. and Japan.

Package of Practices

Agro-climatic Requirements

The crop grows well in both tropical and subtropical climates upto an elevation of 900 m. (above MSL). However, ideal conditions for growing lemon grass are warm and humid climate with sufficient sunshine and 250-330 cm rainfall per annum, evenly distributed over most part of the year. A temperature ranging from 20-300 C and good sunshine throughout the year is conducive to high crop yield with better oil content. In the hilly areas receiving heavy rainfall, the plant grows luxuriantly and is harvested more frequently but the oil and citral content are less as compared to the plants growing in the regions of less rainfall. Lemon grass can also be grown in semi-arid regions receiving low to moderate rainfall.

Soils

It flourishes on a wide variety of soils ranging from loam to poor laterite, calcareous soils. However, well drained sandy-loam soils are ideally suited for better growth, yield and oil content. Soils with poor drainage and with prolonged water logging should be avoided.

Propagation

The crop is propagated through seeds raised in nurseries or rooted slips.

Rooted Slips


For better quality and yield of oil it is recommended to grow lemon grass by slips obtained by dividing well-grown clumps. Tops of clumps are cut off within 20-25 cm of the root. The latter is divided into slips and the lower brown sheath is removed to expose young roots.

Land Preparation

Lemon grass is a perennial crop with a duration of 4 to 5 years. For better growth and establishment, initial land preparation is important. Two to three ploughing followed by making of ridges and furrows are necessary. Application of 10 kg Phorate or 8 to 10 kg neem cake at the time of last ploughing is recommended to control soil borne pests like nematodes, etc.

Planting

Planting is done at the beginning of the rainy season. Depending on the soil fertility status and varieties, seedlings are planted at a distance of 40x40 cm., 45x35 cm., 60x40 cm. Planting on the ridges is suggested especially in high rainfall areas. In case of rooted slips one or two slips are placed into each hole, about 15 cm deep. Planting very deep should be avoided as the plants may develop root-rot during the rainy season.

Irrigation

The improved varieties of lemon grass perform well with supplemental irrigation. Depending upon the rainfall and its distribution the field is to be irrigated at an interval of 3 days during the first month and 7 - 10 day intervals subsequently. After the establishment of plants, irrigation schedule is adjusted depending on water holding capacity of the soil and weather conditions. Four to six irrigation would be critical to sustain the crop yield during summer months.

Nutrition

Manure : Application of FYM @ 10 MT/ha at the time of final land preparation.
Fertilizer : The fertilizer requirements for the crop are best judged based on soil testing and ascertaining the soil fertility status. Keeping in view the biomass harvested from the crop, the normal recommended dose of fertilizers include N, P205 & K20 @ 150: 60: 60 kg/ha/year. Application of 30 kg nitrogen, and entire P2 O5 and K2O per ha as basal dose at the time of planting is recommended. The remaining nitrogen can be applied as top-dressing in 3 to 4 split doses during the growing season. In soils having low fertility levels, the dose of nitrogen should be increased. In zinc deficient soils (Uttar Pradesh), application of zinc sulphate @ 25 to 50 kg per ha. is recommended.

Intercultural Operations

The field is kept free of weeds for the first 3 - 4 months after plating. Similarly, weeding cum hoeing is done up to 1 month, after every harvest. Generally, 2-3 weeding are necessary during a year. In row-planted crops, intercultural operations can be done by a tractor-drawn cultivator or hand-hoe. Application of distillation waste from the crop can be applied as organic mulch @ 3 MT/ha which help in controlling weeds and retaining soil moisture. Chemical weed control through application of Diuron @ 1.5 kg a.i. /ha and Oxyfluorfen @ 0.5 kg a.i. /ha are effective for weed control.

Harvesting and Yield

Lemon grass flowers in winter season. The first harvest is generally obtained after 4 to 6 months of transplanting seedlings. Subsequent harvests are done at intervals of 60-70 days depending upon the fertility of the soil and other seasonal factors. Under normal conditions, three harvests are possible during the first year, and 3-4 in subsequent years, depending on the management practices followed. Harvesting is done with the help of sickles, the plants are cut 10 cm above ground-level and allowed to wilt in the field, before transporting to the distillation site. Depending upon soil and climatic conditions, the plantation lasts on an average, for 4 to 5 years. The yield of oil is less during the first year but it increases in the second year and reaches a maximum in the third year; after this, the yield declines. On an average, 20 to 30 tonnes of fresh herbage is harvested per hectare per annum from 3-4 cuttings. The yield in terms of oil vary from 0.5% to 0.8% depending on the variety, season/month of harvest and age of the crop, with an average oil yield of 0.65%. The yield pattern from the crop is as under :

Post Harvest Processing

Drying

The grass is allowed to wilt for 24 hours before distillation as it reduces the moisture content by 30% and improves oil yield. The oil is extracted from the wilted herb by steam distillation in stainless steel unit. The factors influencing the oil production during distillation are:
  1. Storage of the harvested herbage
  2. Treatment (wilting and cutting into pieces) of the material
www.natureherbs.org