Evaluation of the effects of chelated plus Nano fertilizer on yield factors and some secondary metabolites in Marigold (Calendula officinalis L.)

Introduction: In order to achieve desirable yield based on optimized nutritional management and cost reduction, Nano fertilizer utilization has become abundantly popular. Nano fertilizers accommodate the essential nutrients for the plants incorporated with special carriers at Nano scales. Whereas they exhibit many intense physical and chemical alterations, controlled release in Nano fertilizers is due to a sustained combination of carrier and the nutrients (Sempeho et al., 2014). Foliar application of MnO Nano particles on plants resulted in increased vegetative growth, improved fruit quality, maximum yield and photosynthetic pigments content. By using FeO Nano fertilizers, organic material, protein and lipid content in fruits were also enhanced (Shebl et al., 2019). ZnO nanoparticles increased legume yield in peanut and showed a higher rate of absorption compared to ZnSo4 (Prasad et al., 2012). Strengthening antioxidant activity and increased total phenol after using Nano fertilizer supplements in rice was reported by Singh et al., 2013. Material and methods: A pot factorial experiment based on completely randomized design with two factors and five replications was conducted. First factor included five levels of fertilizer concentrations (0, 1, 2, 3, 4 g L) as foliar application and the second factor was comprised of two levels of foliar spraying (7 and 14 days’ interval). The main growth and yield traits and some of the biochemical characteristics of Marigold flower extract were evaluated at this experiment. Results and discussion: Seven days’ interval of 1 g L Nano fertilizer foliar application resulted in maximum plant height. The maximum plant height (48.10 cm), flower diameter (40.22 mm) and flower number (38.74) were noticed after 1 g L Nano fertilizer at seven days’ interval of foliar application. After seven days interval, by increasing Nano fertilizer concentration, decrease in plant height, flower diameter and flower number was also obvious, whereas fourteen days interval of 3 g L Nano fertilizer increased both traits. Nano fertilizer utilization at fourteen days’ interval resulted an increasing effect on flavone and flavonol content (9.08 mg Quercetin g DW). Seven days’ frequencies of 3 g L Nano fertilizer foliar application, apparently increased total flavonoids (38.20 mg Quercetin g DW). Increasing the Nano fertilizer concentration up to 3 g L, increased total phenolic compounds and fourteen days’ foliar application of Nano fertilizer significantly raised the contents of these compounds compared to seven days’ intervals. By increasing Nano fertilizer concentration, antioxidant activity was reduced but fourteen days’ intervals showed a significant increase in comparison with seven days. 3 g L Nano fertilizer application with seven days’ intervals improved most of the photosynthetic pigments. Conclusions: Generally, these findings confirm the effectiveness of Nano fertilizer application in two intervals on yield factors and active substances contents in Marigold.