The Effect of Nitrogen and Zinc Levels on Essential Oil Yield and some Morphological Traits of Hypericum perforatums

To study the effects of nitrogen and zinc fertilizer on the morphological traits and essential oil yield of St. John’s wort (Hypericum perforatum) a greenhouse experiment in a factorial randomized complete block design with three replications was conducted at University of Tabriz, Iran in 2012. Treatments consisted of three levels of zinc sulphate with a concentration of zinc fertilizer (zero, 3 and 6 parts per thousand) and four levels of nitrogen fertilizer (zero, 50, 100, 150 kg/ha). One half of the fertilizers were applied 20 days after planting of plants and the rest 40 days after transplanting. Traits evaluated were plant height, inflorescence number, leaf area, plant fresh and dry weights and plant essential oil content. The results showed that the traits under study were affected by rate of fertilizer applications. Highest plant height, number of inflorescences, leaf area and essential oil yield were obtained by using 150 kg/ha of nitrogen and applying zinc with 0.006 concentration. Highest fresh and dry weights of above ground parts were also produced by using 150 kg/ha of nitrogen fertilizer along with zinc fertilizer 0.003.