Effect of Organic Fertilization and Seaweed Extract on Growth, Yield, and Bioactive Compounds of Roselle Plant (Hibiscus sabdariffa L)

Abstract

A field experiment was conducted during the spring season of 2025 at a private farm in Al-Jilawiya village, Al-Musayyib district, located about 40 km north of Babil province, Iraq, to evaluate the effect of seaweed extract and animal organic fertilizer on growth, yield, and anthocyanin content of roselle (Hibiscus sabdariffa L.). The experiment was arranged as a factorial experiment in a Randomized Complete Block Design (RCBD) with three replications. The study included three factors: two roselle cultivars (red and purple), three concentrations of seaweed extract (0, 3, and 6 ml L⁻¹), and three levels of animal organic fertilizer (cow manure) (0, 3, and 6 ton ha⁻¹).

    The results showed that the purple cultivar significantly outperformed the local red cultivar in plant height, number of main branches, number of capsules per plant, calyx yield per plant, and anthocyanin content, recording mean values of 64.18 cm, 5.16 branches plant⁻¹, 141.54 capsules plant⁻¹, 46.31 g plant⁻¹, and 0.284%, respectively. The application of seaweed extract at 6 ml L⁻¹ resulted in the highest averages for the studied traits, reaching 169.64 cm for plant height, 5.40 branches plant⁻¹, 163.31 capsules plant⁻¹, 48.13 g plant⁻¹ for calyx yield, and 0.317% anthocyanin content. Similarly, the highest level of organic fertilizer (6 ton ha⁻¹) significantly improved plant growth and productivity, producing the highest mean values of 164.68 cm plant height, 5.47 branches plant⁻¹, 164.44 capsules plant⁻¹, 50.51 g plant⁻¹ calyx yield, and 0.347% anthocyanin content.

    These findings indicate that the combined use of seaweed extract and organic fertilizer can effectively enhance growth, yield, and bioactive compound content of roselle plants under the environmental conditions of central Iraq