Effect of Pinching Date and Potassium Fertilizer rate on Growth and Productivity of Roselle (Hibiscus sabdariffa, L.) Plant

To enhance growth and productivity of roselle plant, two field experiments were done during the two consecutive summer season of 2019 and 2020 at Experimental Farm (Ghazala Farm), Faculty of Agriculture, Zagazig University, Egypt. This study included different pinching time treatments (after 4, 6, 8 and 12 weeks from sowing date) as the main factor and potassium fertilization rate (0.0, 25, 50 and 75 kg K2O/ feddan) as sub-factor as well as their combinations to improve growth, yield, anthocyanin content and some chemical contents of Hibiscus sabbdariffa plant. Results could be summarized as follow: The longest roselle plants were recorded with the control treatment (pinched after 4 weeks from sowing date), whereas pinching after 12 weeks from sowing date increased number of branches/plant. Also, apical bud pinching after 12 weeks from sowing date recorded the highest number of fruits per plant, dry sepals yield/plant and per feddan. Delaying pinching date from 4 to 8 weeks gradually increased anthocyanin content. In addition, total chlorophyll content as well as total carbohydrates, total nitrogen, total phosphorus and potassium percentages were increased with delaying pinching date especially after 12 weeks, in most cases. Potassium fertilization rate at 75 kg per feddan recorded the highest values of growth, yield components and the chemical constituents with significant differences between this rate and the other rates under study. Generally, the combination treatment between pinching after 12 weeks from sowing date and 75 kg potassium fertilization rate had significant effect in most parameters compared to the other combination treatments during both seasons.