Season has a major effect on the essential oil yield response to nutrient supply in Origanum majorana

The effect of different nutrients on growth and essential oil yield and composition in Origanum majorana L. were studied under two seasons differing mainly with respect to their temperature regimes. Oil composition was little affected by either season or nutrient regime. Growth rates and yield of essential oils were positively correlated with nutrient supply; less strongly so in the summer than in late spring. Specific oil yield (yield per unit plant weight) was generally positively correlated with nutrient level at the lower temperature, negatively at higher temperature., In both seasons, the oil yield per plant was closely correlated to the growth rate, regardless of the nutrient or dose, but the responses differed significantly according to the season.