Irrigation and nitrogen requirements of Bergamot mint on a sandy loam soil under sub-tropical conditions

Abstract

A field experiment was conducted with Bergamot mint ( Mentha citrata Ehrh) var. Kiran at Lucknow, India in 1992 and 1993 under four soil moisture regimes (0.6, 0.9, 1.2 and 1.5 irrigation water: cumulative pan evaporation (IW:CPE) ratio) and four levels of nitrogen (0, 80, 160, 240 kg ha −1). Soil moisture regimes maintained at 1.2 IW:CPE ratio significantly 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 produced 86.4% and 10.0% higher fresh herbage than the latter two moisture regimes, with a 63% and 12.7% increase in essential oil yield, respectively. Application of 160 kg N ha −1 was found to be the best with respect 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 proved significantly better for efficient utilization of water and nutrient 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 improved slightly with the higher moisture conditions prevailed during both the harvest. Higher rate of N fertilization (240 kg ha −1) favoured the synthesis of linalool, a major constituent of essential oil only during 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