Effects of different plant densities and nitrogen fertilizer levels on yield and qualitative characteristics of marigold (Calendula officinalis L.)

In order to evaluate the effects of different plant densities and nitrogen levels on growth, yield and qualitative characteristics of marigold, a field experiment was conducted as split plot based on randomized complete block design with four replications at the Agricultural Research Station, Azad University of Torbat-e-Jam, during growing season of 2008-2009. Main and sub plots were four nitrogen levels (zero, 30, 60 and 90 kg.ha-1) and three plant densities (25, 50 and 75 plants.m-2), respectively. Nitrogen (as Urea) was used at 4-6 leaves and flowering stages of marigold. The results showed that the simple effects of nitrogen and plant densities were significant (p≥0.05) on plant height, shoot, root, seed and flower dry weights, biological yield, harvest index and essential oil and extract contents of marigold. Interaction between nitrogen level and plant density had not significant effect on studied traits. By increasing nitrogen level from zero to 60 kg.ha-1, enhanced flower dry weight and essential oil content due to increasing in vegetative growth and photosynthesis up to 100% and by increasing nitrogen level up to 90 kg.ha-1, dry weight and essential oil content declined 33 and 52%, respectively. Whereas, by enhancing in plant density from 25 to 50 plants.m-2, increased flower dry weight and essential oil content up to 23 and 29% and by increasing in nitrogen level up to 75 plants.m-2, dry weight and essential oil content decreased 20 and 44%, respectively.