Effects of Azocompost and urea on the herbage yield and contents and compositions of essential oils from two genotypes of dragonhead (Dracocephalum moldavica L.) in two regions of Iran

Dragonhead is an annual, herbaceous, balm-scented and spicy aromatic member of the family Lamiaceae. We examined effects of different sources of nitrogen on the content and composition of essential oils in two genotypes of dragonhead in two regions of Iran. The sources of nitrogen used were 100% urea (70 kg N ha−1), 75% urea (52.5 kg N ha−1) + 25% Azocompost (3.85 ton ha−1), 50% urea (35 kg N ha−1) + 50% Azocompost (7.77 ton ha−1), 25% urea (17.5 kg N ha−1) + 75% Azocompost (11.55 ton ha−1), and 100% Azocompost (15.55 ton ha−1). Optimal yield and content of essential oil at both locations for both genotypes were obtained by applying 50% urea + 50% Azocompost. Geraniol, geranial, and geranyl acetate were the most abundant compounds. For both genotypes and both locations, application of 50% urea + 50% Azocompost increased levels of geraniol and geranial, and application of Azocompost alone increased levels of geranyl acetate. Overall, we conclude that the application of 50% urea with 50% Azocompost is recommended for optimising the content and composition of essential oils in dragonhead.