Response of lemongrass (Cymbopogon flexuosus) under different levels of irrigation on deep sandy soils

The growth and herbage and oil production of East Indian lemongrass (Cymbopogon flexuosus) in response to different levels of irrigation water (IW) [0.1, 0.3, 0.5, 0.7, 0.9, 1.1, 1.3 and 1.5 times cumulative pan evaporation (CPE)] were evaluated on deep sandy soils at the research farm of the Central Institute of Medicinal and Aromatic Plants, Lucknow, from 1991 to 1993. In general, an increment in the level of irrigation increased the plant height up to 0.7 IW:CPE ratio. The response of irrigation levels on tiller production of lemongrass differed with the season of harvest. Maximum tillers/clump during the 2nd, 3rd, 6th and 7th harvests were in response to irrigation levels 0.9, 0.5, 0.7 and 0.7 IW:CPE ratio, respectively. Oil content had an inverse relationship with the levels of irrigation, specially during the 1st, 2nd, 5th and 6th harvests. Significantly higher herb and essential oil yields were recorded at 0.7 IW:CPE ratio, irrespective of season of harvest. The maximum total herb (22.79 t/ha in first year and 33.11 t/ha in second year) and oil (146.2 l/ha in the first year and 205.3 l/ha in the second year) yields were recorded at 0.7 IW:CPE ratio. The quality of oil with respect to the major chemical constituents (Citral-a, Citral-b and geraniol) was not changed. At the optimum level of irrigation (0.7 IW:CPE ratio) the water used by lemongrass was 118.2 cm for first year and 123.8 cm for the second year. Water-use efficiency was found to be higher (1.66 l oil/ha-cm) in the second year than the first year (1.23 l oil/ha-cm). For optimum yield potential of lemongrass on deep sandy soils of sub-tropical climate, the crop received 17 irrigations in the first year and 14 irrigations in the second year of harvests. Irrigations were made during the dry winter and summer months.