Effects of foliar application and use of vermicompost on quantitative and qualitative characteristics of roselle (Hibiscus sabdariffa L.)

Roselle (Hibiscus sabdariffa L.) is a valuable medicinal plant widely used in the pharmaceutical, food, and industrial products. In order to investigate the effects of vermicompost and seaweed foliar application on quantitative and qualitative traits of roselle, this research was carried out in Islamic Azad University, Isfahan Branch in spring, summer and autumn of 2016. The experiment was conducted as factorial in the form of a randomized complete block design with three replications. Vermicompost treatments were applied on four levels: zero (control), 5, 10 and 15 ton/ha, and seaweed spraying at three levels: 0 (control), 1 and 1.5g/L at intervals of one month. At the end of experiment, plant height, number of flowers, fresh and dry weights of the plant, fresh and dry weights of calyx, chlorophyll a, b and total, anthocyanin content, vitamin C, flavonoids and titratable acidityof calyx were measured. The results indicated that the use of seaweed and vermicompost improved the quantitative and qualitative characteristics of roselle. The highest plant height, number of flowers per plant, fresh and dry weights of plant and calyx, chlorophyll a, b and total, anthocyanin content, titratable acid, and vitamin C in calyx, were measured in vermicompost 15 ton/ha. Also the highest amount of chlorophyll a, anthocyanin, flavonoids, titratable acid, and vitamin C of calyx, number of flowers per plant and fresh weight of plant were measured in 1.5 g/l seaweed. The highest amount of vitamin C (68.74 mg/100g), titratable acid (4.97%), anthocyanin (1.400mg/g) in calyx, number of flowers per plant (73.33) and plant fresh weight (828.33 g) were observed in vermicompost 15 ton /ha with the foliar application of seaweed 1.5 g/l.