Effect of biological nitrogen on the harvest index of flower and essential oil of Calendula officinalis L. under End Season Water Deficit Condition

ABSTRACT: To evaluate effect of irrigation disruption on the harvest index of flower and essential oil of Calendula officinalis L., an experiment was conducted as split plot at the Research Farm of Faculty of Agriculture, Urmia University (latitude 37.53 °N, 45.08 °E, and 1320 m above sea level) in 2010. Treatments included end season water deficit (irrigation disruption at first, second, third harvest and without disruption as control) as main plot and amount of biological nitrogen (0, 3, 6, and 9 liter per hectare of biological nitrogen included Azotobacter and Azospirillum sp.) as sub plot were arranged in randomized complete block design with three replications. Data analysis of variance showed the significant interaction effect between irrigation disruption and biological nitrogen on essential oil and flower harvest index in first harvest, second harvest, third harvest, fourth harvest, fifth harvest and sum of total harvest. The highest harvest index of essential oil (0.38 %) in sum of total harvest belonged to irrigation disruption after first harvest and 9 liter per hectare of biological nitrogen. The maximum flower harvest index in in sum of total harvest (11.8 %) was obtained from control treatment of irrigation (without irrigation disruption) and 9 liter per hectare of biological nitrogen.