Effect of sowing date and different levels of nitrogen fertilizer on yield and essence of flower in medicinal plant of Calendula officinalis L.

Management of chemical fertilizers application is very important in their effect on environment and plant yield especially in arid and semi-arid region. In order to determine the effect of different sowing date and levels of nitrogen fertilizer on yield, morphological characteristics and essence of Calendula officinalis a field experiment was conducted using split plot on the basis of randomized complete block design with three replications at Agriculture Research Center of Sistan, Iran during 2008-2009. Main plots were consisted of sowing date in 3 levels, 1th, 15th and 30th of April and sub plots included levels of nitrogen fertilizer in 2 levels (50 and 100 kg/ha) (to be consistent with the rest of the work). The evaluating factors were weight of stem, the number of flower in 5 plants, weight of fresh flower, weight of dry flower and essence content. The results of main effects of compound variance analysis including sowing date and nitrogen fertilizer showed that sowing date on April 1st and 50 kg/ha of nitrogen fertilizer had the most effect in increasing these factors. Also, interaction effects of sowing date  nitrogen fertilizer was significant at 5% probability level on all factors. In general, the results of this research demonstrated that using of suitable sowing date along with consumption of 50 kg/ha nitrogen increase yield and essence of C. officinalis.   Key words: Calendula officinalis, sowing date, nitrogen fertilizer, yield, essence.