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ABSTRACT
In the present study the effect of different nitrogen amounts (0 g [N0], 0.45 g [N1], 0.9 g [N2] and 1.35 g N [N3] per pot, corresponding to 0 kg·ha−1, 50 kg·ha−1, 100 kg·ha−1 and 150 kg·ha−1 N application in field conditions) and application times (at sowing, vegetative stage and pre-bloom stage) on the yield, relative water content, total nitrogen content and nitrogen use efficiency in plants of the Achillea millefolium group-related cv. Proa was investigated. Antioxidant activity, flavonoid content, rate and composition of the essential oils were also determined. Application of N2 increased the dry herbage and flos production, total nitrogen amount and nitrogen use efficiency, without affecting the essential oil rate while reducing the antioxidant activity. Higher amounts (N3] of nitrogen maintained the dry herbage and flos yield at levels similar to N2 but decreased the antioxidant activity and rate of the essential oil. The major component of the essential oil, chamazulene, was negatively (N1, N2) or not influenced (N3] by the nitrogen application, while variable changes were registered in the content of the other components. The data point to the nitrogen regime being a subtle tool for regulating the performance of cv. Proa plants.