Investigation of Quantitative Yield and Some Morphological Traits of Roselle (Hibiscus sabdariffa L.) in Response to Different Planting Pattern and Integrated Fertilizer Management

Background and Objectives: Roselle (sour tea) is a multipurpose plant with various applications, including use as a food, medicinal, and ornamental plant. The aim of this research was to investigate the effects of planting arrangement and integrated fertilizer management (plant nutrition) on quantitative and economic traits. 
 
Materials and Methods: The experiment was conducted as a split-plot design in a randomized complete block arrangement with three replications at the educational Farm of the plant production and genetics department, Shahid Chamran University of Ahvaz during the 2022-2023 growing season. The main plot treatments consisted of four ridge planting systems: 50 cm row spacing (conventional furrow), 50 cm row spacing (wide furrow), 75 cm row spacing (conventional furrow), and 75 cm row spacing (wide furrow). The subplot treatments included five integrated nutrient management systems: chemical fertilizer (control), integrated treatment A (chemical base (100% N-P-K) with cattle manure and humic acid), integrated treatment B (chemical base (75% N-P-K) with super nitroplus biofertilizer, barvar-2 phosphate biofertilizer and micronutrient mixture), organic treatment A (compost, super nitroplus, Biosulfur, Barvar-2, humic acid and jasmonic acid), and organic treatment B (vermicompost, mycorrhizal fungi, super nitroplus, salicylic acid, melatonin, and ellagic acid).
 
Results: The evaluated plant traits and indices included characteristics related to yield components such as plant height, number of capsules, number of seeds per capsule, number of lateral branches, dry weight of leaves, dry weight of stems and lateral branches, dry weight of capsules, 1000-seed weight, dry weight of calyx, and economic yield index. The results indicated that the maximum plant height (236.6 cm), number of capsules (42.6 capsules per plant), number of seeds per capsule, number of lateral branches (6.7 lateral branches), dry weight of capsules (1.52 g), dry weight of leaves (25.7 g per plant), dry weight of stems and lateral branches (227 g per plant), and economic harvest index (calyx) (8.7%) were achieved in the 75 cm wide planting arrangement with integrated fertilizer A. The highest 1000-seed weight (48.8 g) was obtained in the 75 cm wide planting arrangement with organic fertilizer B (48.8 g), and the highest economic yield was achieved in the 50 cm conventional planting arrangement with integrated fertilizer A (0.73 g). Correlation analysis between traits revealed that the dry weight of capsules and calyx, which are among the most important quantitative and yield-related traits of roselle, had a strong and positive correlation (0.99) with each other.
 
Conclusion: Research indicates that in tropical and subtropical regions, the warm-adapted roselle achieves optimal economic yield when grown under specific conditions temperatures around 27°C during the reproductive stage, combined with wide furrow that promotes extensive lateral branching and greater vegetative growth space. Furthermore, the integrated application of combined fertilizer treatment A (N.P.K chemical fertilizers) with (cattle manure and humic acid) consistently produces excellent quantitative yield outcomes, demonstrating the plant's positive response to balanced nutrient management in these climatic conditions.