Effects of organic fertilizers application on morphophysiological characteristics of calendula (Calendula officinalis L.)

The present study aimed to investigate the effect of application of organic fertilizers on the yield of medicinal plant, calendula (Calendula officinalis L.). The experiment was conducted in a randomized complete block design with 10 treatments and 3 replications in the research farm of Zanjan University. Treatments included cattle manure, poultry manure, and vermicompost, each at three levels (5, 10, and 15 tons per hectare) and control (without fertilizer). The measured traits were the thousand seed weight, number of capitules per plant, leaf area, plant height, petal dry weight, capitule diameter, chlorophyll content index, flavonoids, carotenoids, and essential oil percentage. Data were analyzed by SAS software, and mean comparisons was performed by Duncan's test. The results showed significant effects of fertilizer on thousand seed weight, capitule number per plant, leaf area, carotenoids, and essential oil percentage at p≤0.01, and plant height, petal dry weight, and flavonoid at p≤0.05. The type of fertilizer had no significant effect on capitule diameter and leaf chlorophyll content. Overall, the results showed that using organic fertilizers had favorable impact on yield, growth characteristics, and active ingredients content of Calendula.