Effect of nitrogen‐application rate on the biomass, concentration, and composition of essential oils in the leaves and roots of three types of parsley

The effect of four levels of nitrogen (N) application (3.2, 16.2, 32.4, and 48.6 g m–2) on the biomass and concentration and composition of essential oils of three parsley types (plain leaf, turnip‐rooted, curl leaf) was investigated in order to determine the optimum N level for oil production by this crop. The concentration of essential oils in the roots and leaves of plain leaf parsley and turnip‐rooted parsley was not affected by N application, but decreased with increasing N rate in curl leaf parsley. However, because the mean foliage biomass for all three types was about 2.5 times higher at 16.2 g m–2 N than in the low‐N‐rate treatment, the mean foliar oil yield increased from 0.68 to 1.38 g m–2. Root biomass increased by a factor of 1.7 at 16.2 g m–2 N (compared to the low‐N‐rate treatment), but oil yield increased only marginally from 0.3 to 0.4 g m–2. The composition of the essential oils of roots and leaves differed between parsley types. Increasing N application caused a reduction in the percentage of β‐phellandrene in the essential oils of parsley leaves. In turnip‐rooted parsley, increasing N caused a reduction in the percentage of myristicin and apiole. Because these three components of the essential oils contribute to parsley aroma, it may be concluded that although application of N fertilizer leads to higher parsley biomass and oil yield per plant, the essential oil components may change and aroma quality may be affected negatively.