Effects of different nitrogen levels and plant density on flower, essential oils and extract production and nitrogen use efficiency of Marigold (Calendula officinalis).

Efficient use of nitrogen for medicinal plants production, might increase flower dry matter, essential oil and extract yield and reduce cost of yield production. A two year (2005 and 2006) field study was conducted in Torogh region(36,10° N,59.33° E and 1300 m altitude) of Mashhad, Iran, to observe the effects of different nitrogen and densities on flower dry matter, essential oil and extract production and nitrogen use efficiency (NUE) in a multi-harvested Marigold (Calendula officinalis). The levels of Nitrogen fertilizer (N) were 0, 50, 100 and 150 kg ha-1 and levels of density were 20, 40, 60 and 80 plant m-2. The combined analysis results revealed significant effects of N and density levels on flower dry matter, essential oil and extract production and NUE of Marigold. The highest dry flower production obtained by 150 kg ha-1 N and 80 plant m-2 plant population (102.86 g m-2). The higher flower dry matter production caused more essential oil and extract production in high nitrogen and density levels. Agronomic N-use efficiency (kg flower dry matter yield per kg N applied), physiological efficiency (kg flower dry matter yield per kg N absorbed) and fertilizer N-recovery efficiency (kg N absorbed per kg N applied, expressed as %) for marigold across treatments ranged from 6.8 to14.9, 12.3 to 33.6 and 55.5 to 77.6, respectively and all were greater for N application at 50 compared with150 kg N ha-1, and under high density than low density. The amount of essential oil and extract per 100g flower dry matter decreased during the flower harvesting period. The higher amount of essential oil and extract obtained at early flowering season. The essential oil and extract ranged from 0.22 to 0.12 (ml. per 100g flower dry matter) and 2.74 to 2.13 (g per 100g flower dry matter) respectively.