Improving Growth and Productivity of Roselle Plant through Foliar Application of Organic Stimulants (Citrein and Nofatrein) as Microelement Sources under Reduced Chemical Fertilization

Roselle (Hibiscus sabdariffa L.) is a nutrient- and anthocyanin-rich medicinal plant whose growth and productivity may be sustainably enhanced by natural bio-stimulants such as Citrein (CT) and Nofatrein (NF) while reducing dependence on chemical fertilizers. The objective of this investigation was to study the positive effects of foliar spraying application with CT and NF on vegetative growth parameters: plant height (cm), number of main branches/plant, fresh and dried weights of sepals per plant (g), No. of fruits/plant and chlorophyll content (SPAD units). In addition to some chemical components: vitamin-C content (mg/100g), total acidity %, K%, and total anthocyanin content (mg/100g) and dry sepals yield (kg/fed.) of Roselle, under two levels: 75 and 100 % from recommended fertilization level (N, P and K) soil. The present study was conducted during the 2024/2025 seasons at the Sabahia Horticulture Research Station, Alexandria Governorate, Egypt. The treatments were: control, CT at 0.1, 0.2 or 0.3% and NF at 0.1, 0.2 and 0.3% under two levels of chemical fertilization (75 and 100%) in both seasons. In general, the obtained results indicated that vegetative growth parameters, chemical constituents and yield of dry sepals (Kg/fed.) increased with application of the different treatments under two levels: 75 and 100% of N, P, and K fertilizer. The maximum values were obtained from the treatments; 0.3%, 0.2 % of NF and 0.3% of CT. From the above, we recommend spraying with NF at 0.3% or 0.2% or CT at 0.3% two sprays/season to obtain high quality and productivity of Roselle, under level (75%) of N, P, and K fertilizer, which lead to reduced use of chemical fertilizers, the production of a safe product and minimizing the environmental pollution caused by mineral fertilizers.