Effect of Compound NPK Fertilizer and Zeolite on Growth, Yield, and Certain Secondary Metabolites in Different Roselle <i>(Hibiscus sabdariffa</i> L.) Genotypes

Abstract A field experiment was conducted in 2024 at a private farm in the Hor Rijab area, Baghdad Governorate, to evaluate the effect of compound fertilizer and zeolite on the growth, yield, and active compounds of four roselle (Hibiscus sabdariffa L.) genotypes: Hit Black, Sudan 3, Areib, and Hit Red. The treatments included control (no fertilizer), zeolite at 100 kg ha −1 , NPK (20:20:20) at 250 kg ha −1 , and a combination of NPK 250 kg ha −1 + zeolite 100 kg ha −1 . The experiment followed a randomized complete block design (RCBD) in a factorial arrangement with three replications, totaling 48 experimental units. The results showed significant differences among treatments. The Hit Black genotype recorded the highest values for plant height (137.99 cm), number of branches (31.78), number of leaves (498.23), number of capsules (61.99), 1000-seed weight (37.43 g), and total seed yield (654.22 kg ha −1 ). It also showed higher concentrations of active compounds, including ferulic acid (4.52 ppm), quercetin (6.3 ppm), rutin (10.6 ppm), chlorogenic acid (1.7 ppm), and caffeic acid (2.8 ppm). The combined application of NPK and zeolite significantly improved all growth and yield parameters, achieving the highest values in yield (695.42 kg ha −1 ) and gallic acid (7.4 ppm). The interaction between the Hit Black genotype and the NPK + zeolite treatment showed the best overall performance, while Sudan 3 recorded the highest number of seeds per capsule under the same treatment.