IRRIGATION AND NITROGEN REQUIREMENTS OF BERGAMOT MINT ON A SANDY LOAMSOIL UNDER SUBTROPICAL CONDITIONS

A field experiment was conducted with Bergamot mint (Mentha citrata Eh rh) var. Kiran at Lucknow, India in 1992 and 1993 under four soil mois ture regimes (0.6, 0.9, 1.2 and 1.5 irrigation water: cumulative pan e vaporation (IW:CPE) ratio) and four levels of nitrogen (0, 80, 160, 24 0 kg ha-1). Soil moisture regimes maintained at 1.2 IW:CPE ratio signi ficantly increased the crop growth, and herb and essential oil yields as compared with those having 0.6 and 0.9 IW: CPE ratio. The former pr oduced 86.4% and 10.0% higher fresh herbage than the latter two moistu re regimes, with a 63% and 12.7% increase in essential oil yield, resp ectively. Application of 160 kg N ha-1 was found to be the best with r espect to the yield of the crop, but increased levels beyond this did not cause deleterious effects on the synthesis of monoterpenes in the essential oil. High moisture regimes maintained during summer months p roved significantly better for efficient utilization of water and nutr ient by the crop. The quality of the essential oil in terms of its two major constituents, linalool and linalyl acetate increased favourably up to 1.2 IW:CPE ratio, while the former decreased and the latter imp roved slightly with the higher moisture conditions prevailed during bo th the harvest. Higher rate of N fertilization (240 kg ha-1) favoured the synthesis of linalool, a major constituent of essential oil only d uring the first harvest. It is concluded that the Bergamot mint should be irrigated at 1.2 IW:CPE ratio with an application of 160 kg N ha-1 in the sub-tropical climate of India.