Evaluation of yield, chemical composition and yield of essential oil of four cultivars of sweet basil (Ocimum basilicum L.) affected by different levels of nitrogen

A field experiment was conducted to evaluate yield and some qualitative characteristics of four cultivars of sweet basil treated with different levels of nitrogen fertilizer. The experiments were located on the Agricultural Research Station of Khorramabad, Iran, during the 2016-2017 growing season. Treatments were arranged in factorial split-plot-in time in randomized complete block design with three replications. Experimental treatments were four cultivars of sweet basil (Ocimum basilicum ‘Italian Large Leaf’, O. basilicum ‘Mobarakeh’, O. basilicum ‘Cinnamon’ and O. basilicum ‘Thai’), three levels of nitrogen fertilizer (0, 100 and 200 kg ha-1 urea) and three harvests. The highest total dry mass (3482.4 kg ha-1) was related to ‘Italian Large Leaf’ with the application of 200 kg ha-1 urea at the second harvest. The maximum (26.79 kg ha-1) essential oil yield belonged to 100 kg ha-1 urea. The highest concentrations of main constituents of essential oil, except methyl chavicol, 1,8-cineole and methyl cinnamate were obtained by control (without nitrogen fertilizer). Italian Large Leaf cultivar and application of 100 kg ha-1 urea are recommended to access an acceptable agricultural yield and essential oil yield in sweet basil under the environmental condition similar to Khorramabad