Influence of irrigation and nitrogen on herbage and oil yield of palmarosa (Cymbopogon martinii) under semi-arid tropical conditions

Influence of irrigation and nitrogen on herbage and oil yield of palmarosa (Cymbopogon martinii) under semi-arid tropical conditions

European Journal of Agronomy 14 (2001) 157 – 159 www.elsevier.com/locate/eja Short communication Influence of irrigation and nitrogen on herbage and...

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European Journal of Agronomy 14 (2001) 157 – 159 www.elsevier.com/locate/eja

Short communication

Influence of irrigation and nitrogen on herbage and oil yield of palmarosa (Cymbopogon martinii ) under semi-arid tropical conditions M. Singh *, S. Sharma Central Institute of Medicinal and Aromatic Plants, Field Station, Allalasandra, G.K.V.K Post, Bangalore, 560 065, India Received 21 April 1999; received in revised form 29 October 1999; accepted 3 July 2000

1. Introduction

2. Materials and methods

Palmarosa (Cymbopogon martinii Roxb. Wats Var. motia) is a perennial, multi-harvest aromatic grass cultivated in different parts of the world. On hydrodistillation, inflorescence and leaves of palmarosa yield essential oil, rich in geraniol (70 – 90%), which is used extensively in perfumery, flavouring and cosmetic industries the world-over. The crop is being cultivated in large areas and the application of nitrogen fertilizer was found to increase herbage and oil yields (Prakasa Rao et al., 1985; Rajeswara Rao et al., 1991; Yadav et al., 1985). There is, however, a paucity of information on the influence of irrigation and nitrogen application on palmarosa. Therefore, field experiments were conducted to study the effect of irrigation and nitrogen application on certain growth characteristics, herbage, oil yields and oil quality.

A field study was conducted for 2 years (1995– 97) in an irrigated red sandy loam (Alfisols) soil at the Central Institute of Medicinal and Aromatic Plants, Field Station farm, Bangalore, India. Bangalore is situated at 13°05%N and 77°35%E and is 930 m above mean sea level. The soil (0–30 cm) characteristics were: pH 6.5, and organic carbon, 0.35%. The soil had 150 kg ha − 1 of alkaline KMnO4 extractable N (Subbaiah and Asija, 1956); 11 kg ha − 1 of 0.5 M NaHCO3 extractable P and 210 kg ha − 1 exchangeable K. The water holding capacities of the soil were 15.6 and 6.5% at − 0.3 and −1.5 Mpa, respectively and bulk density was 1.5 g cc − 1. The treatments consisted of three levels of irrigation (0.25, 0.50 and 0.75 IW: CPE ratios — IW is the depth of irrigation water and CPE was the cumulative daily evaporation from the Standard USWB Class A Open pan) and three levels of N (0, 100 and 200 kg ha − 1) and were arranged in a split-plot design with three replications. Irrigation level treatments were in the main plots and N rates in the subplots. A progressive total of evap-

* Corresponding author. Tel.: +91-80-8460563.

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3. Results and discussion

oration, after accounting for rainfall, was maintained and irrigation was scheduled on attaining the pre-determined value of CPE. Thus, CPE values for different IW/CPE ratios viz., 0.25, 0.50 and 0.75 at a constant depth of 30 mm IW were calculated to be 120, 60 and 40 mm, respectively. The quantity of irrigation water, let out to cover each plot size of 9.45 m2 was measured by water meter. Thirty day old healthy seedling of palmarosa var. motia were planted in the first week of October 1995 with a 30 ×45 cm plant to row spacing. At planting, uniform rates of fertilizer application of 17.5 P and 35.7 kg K ha − 1 were applied as a basal dose and N was applied in the form of urea, in eight equal splits at 45 day intervals. Plant height and number of tillers per plant were recorded before each harvest. Four harvests were taken during each year (February, April, June and September) at the flowering stage. The crop was harvested 20 cm above the ground level and plotwise fresh herbage yield was recorded from an area of 5.4 m2. The oil content in the fresh herbage was estimated using Clevenger’s apparatus. Two of the important chemical constituents of palmarosa oil, geraniol and geranyl acetate were determined by gas chromatography. Pooled data for 2 years were analysed using the lay out of a split-plot design.

Plant height significantly increased with an increase in irrigation levels up to a 0.75 IW: CPE ratio in the first three harvests and 0.50 IW:CPE ratio in the fourth harvest which was taken in the rainy season. The number of tillers per plant showed a similar trend up to 0.50 IW:CPE in the first and third harvests and in the second and fourth harvests at the 0.75 IW:CPE ratio. Both these traits were significantly influenced by increasing the N rate to 200 kg ha − 1. These trends may be due to rapid proliferation of root biomass resulting in higher absorption of nutrients and water from the soil leading to the production of higher vegetative biomass (Taylor and Klepper, 1978; Hamblin, 1985). Fresh herbage and essential oil yields increased significantly up to the 0.75 IW:CPE ratio compared with those of the 0.25 and 0.50 IW:CPE ratio. The low oil yield obtained at the 0.25 IW:CPE ratio was attributed to moisture stress which adversely affected crop growth. Similar results were earlier reported in the case of lemongrass (Singh, 1998). The application of 200 kg N ha − 1 produced significantly greater fresh herbage and essential oil yields compared to that with 0 and 100 kg N ha − 1. These results are in close conformity to those of Prakasa Rao et al., 1985 and Yadav et al., 1985.

Table 1 Herbage and essential oil yields of palmarosa as influenced by soil moisture regimes and nitrogen rates (pooled data for 2 years) Treatment

Herbage yield (t ha−1)

Essential oil yield (kg ha−1)

Nitrogen rate (kg ha−1)

Nitrogen rate (kg ha−1)

0 Soil moisture regime (IW:CPE ratio) 0.25 0.50 0.75 C.D. (p = 0.05)a Moisture regime Nitrogen Moisture regime×nitrogen a

C.D. — critical difference at 5%.

14.37 19.77 25.86

100

28.13 32.72 43.14 2.63 2.48 4.20

200

32.28 42.53 53.33

0

78.32 109.28 135.85

100

200

142.15 178.65 226.25

175.88 253.61 292.49

37.52 15.67 27.14

M. Singh, S. Sharma / Europ. J. Agronomy 14 (2001) 157–159

Interaction effects between irrigation and N rates were significant for the production of herbage and oil yields (Table 1). Irrigating palmarosa at a 0.75 IW:CPE ratio along with 200 kg N ha − 1 gave maximum herbage and oil yields compared with other ratios. Water use efficiency (WUE) was lowest in a wet regime (0.75 IW:CPE) and highest in a dry regime (0.25 IW:CPE). This may be due to the dilution effect. Similar findings were reported earlier in lemongrass (Singh, 1998) and sugarcane (Yadav and Prasad, 1988). Higher WUE with an increased N rate may be due to the higher herbage production. The content of oil and its components, geraniol and geranyl acetate did not vary appreciably with changes in N application rates or moisture regimes. Thus, for the maximum production of essential oil palmarosa could be given 27 supplementary irrigations (0.75 IW:CPE ratio) and fertilized with 200 kg N ha − 1 year − 1 in the semi-arid tropical climate of India.

References Hamblin, A.P., 1985. The influence of soil moisture on wa-

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