Pre-Flowering Harvesting of Ocimum gratissimum for Higher Essential Oil and Eugenol Yields Under Semi-Arid Tropics

Journal of Essential Oil Research: JEOR, Mar/Apr 2005 by Kothari, Sushil K, Bhattacharya, Arun K, Singh, Kamla, Ramesh, Srinivas I, Et al

Second field experiment was initiated in June 2000 in the same block of the research farm. The experiment was laid out in a randomized block design with five treatments on stage of crop harvest (pre-flowering and 25%, 50%, 75% and 100% flowering) and four replications, individual plots being 3 x 6 m. Each plot received uniform dose of neem cake 900g(0.5t/ha),di-ammonium phosphate 155 g (40 Kg P^sub 2^O^sub 5^/ha) and muriate of potash 120 g (40 kg K^sub 2^O/ha) as basal dose which was incorporated with 5 cm top soil using hand hoe. Ocimum gratissimum seedlings, six weeks old, were planted at 60 cm row-to-row and 45 cm plant-to-plant spacing in June 2000. The field was irrigated immediately after planting for early establishment of the seedlings. Thereafter, the field was irrigated 11 and 13 times in the first and second year of experimentation, respectively. Nitrogen at 120 kg/ha was applied in the form of urea spreading over all the harvests per annum. The crop received five and four hand weedings during first and second year of experimentation. Apical part (25-35 cm) of all the branches was harvested in all the treatments as given below:

Biomass yield was recorded plot-wise at each harvest and essential oil content in biomass was determined and the GC analysis of the oil samples from first harvest were performed as stated earlier.

All the data from second experiment were subjected to statistical analysis of variance (ANOVA) technique as applicable to randomized block design (19).

Results and Discussion

Ocimum gratissimum cv. Indian is perennial in growth habit with moderate plant height 76.5 ±5.1 cm and spread 58.1 ± 6.3 cm, number of branches/plant 14.5 ± 3.0, leaf color green (ventral surface) to dark green (dorsal surface), shape ovate, margin crenate serrated, size 48.3 ± 17.7 cm^sup 2^ and number/plant 670 ± 51, inflorescence color greenish with violet tinge, length 17.1 ± 2.8cm, diameter 1.65 ± 0.15 cm and number/plant 90.7 ± 8.9 and flower color white and diameter 2.5 ± 0.5mm. On an average, contribution of leaves, stalks and inflorescences were 59%, 23% and 18% to total plant biomass and 80%, 1% and 19% to the total oil yield, respectively (Table I). Oil content in stalk being very low, its contribution to total oil yield was negligible. On the contrary, leaf contribution to total oil yield was very high because of higher leaf biomass and oil content. A marked variability was observed in respect of composition of the oils from leaves and inflorescences (Table II). The leaf oil was richer in eugenol but simultaneously had lower (E)-β-ocimene, as compared to inflorescence oil. Remarkable variability in volatile constituents from leaves and inflorescence oil of O. tenuiflorum (12), O. micranthum (14), O. basilicum (13), and Cameroon-type O. gratissimum (8), has also been reported. The oil distilled from whole herb contained eugenol as the dominant compound which corresponds to earlier reports on oil composition of O. gratissimum grown in India (3,4).