The effect of different nitrogen fertilization rates on yield and quality of marigold (Calendula officinalis L. 'Tokaj') raw material

Pot marigold (Calendula officinalis L.) is an annual ornamental plant which is also grown for herbal raw material (flower heads) used in the pharmaceutical and cosmetic industries. A field experiment was carried out in the years 2006-2008 in the Experimental Farm of the University of Life Sciences in Lublin. The study was conducted on loess soil with the granulometric composition of silt loam. The aim of the experiment was to determine the effect of different nitrogen rates (0, 40, 80, 120, 160 kg N × ha-1) on some morphological features of flower heads as well as on yield and quality of pot marigold raw material. Flowering of pot marigold was shortest in the control treatment (32 days) and longest (43 days) in the plot where nitrogen fertilization had been applied at the highest rate (160 kg N × ha-1). Nitrogen fertilization had a significant influence on the number of flower heads per plant, but no significant difference was found in diameter as well as in ligulate flowers and tubular flowers in the flower head. It was found to increase significantly raw material yield after the application of 80 kg N × ha-1, compared to the control treatment. Yield of flower heads did not differ markedly for fertilization rates from 80 to 160 kg N × ha-1. Nitrogen fertilization modified slightly essential oil content (this content increased with increasing nitrogen rates), but at the same time it decreased the percentage of flavonoid compounds