Enhancing Okra Productivity and Nutritional Quality With Organic Fertilizers: Comparative Effects on Growth, Yield, and Bioactive Compounds

Okra constitutes a crop of significant nutritional and economic relevance, particularly within the African context. It frequently exhibits constrained productivity and suboptimal nutritional quality under conventional mineral fertilization regimes, which are also associated with adverse environmental externalities. There is therefore an urgent need to comparatively evaluate the efficacy of contrasting organic fertilizers in concurrently enhancing growth performance, yield components, and the accumulation of bioactive compounds in okra, within a framework of sustainable agronomic intensification. This study evaluated the influence of organic and chemical fertilization on the biochemical quality of okra fruits. A randomized complete block design was implemented to test different fertilization treatments: mineral fertilizer (200 kg/ha NPK), poultry manure (5 and 10 t/ha), rabbit urine (1000 and 2000 L/ha), and combinations of poultry manure with rabbit urine (poultry manure, 5 t/ha + rabbit urine, 1000 L/ha; poultry manure, 10 t/ha + rabbit urine, 2000 L/ha; poultry manure, 5 t/ha + rabbit urine, 2000 L/ha; poultry manure, 10 t/ha + rabbit urine, 1000 L/ha). The okra cultivar Kirikou F1 was used and planted at a spacing of 0.4 × 0.5 m, corresponding to a population density of 50,000 plants ha −1 . Growth and yield variables were evaluated. Quantification of phenolic compounds, soluble sugars, proteins, flavonoids, and carotenoids was performed via UV–visible spectrophotometry, while enzymatic activities and mineral contents were also assessed. The results revealed that the combined application of poultry manure (5 t/ha) and rabbit urine (2000 L/ha) significantly enhanced both the growth performance (plant height and collar diameter) and yield of okra. Phytochemical screening identified alkaloids, anthraquinones, and terpenes in the fruits in some treatments; however, tannins were absents in all the treatments. The treatments clearly changed the composition of the okra fruits, but the effect varied depending on the measured variable. For total phenolic compounds, the treatments combining poultry manure and rabbit urine, especially those based on T6 (poultry manure, 5 t/ha + rabbit urine, 1000 L/ha); T7 (poultry manure, 10 t/ha + rabbit urine, 2000 L/ha); T8 (poultry manure, 5 t/ha + rabbit urine, 2000 L/ha); and T9 (poultry manure, 10 t/ha + rabbit urine, 1000 L/ha), appeared to be the most effective, whereas the T0 control showed the lowest values. For total soluble sugars, the same organic combinations and some applications of rabbit urine alone were generally more favorable than the control and NPK alone. Regarding total proteins, the enriched treatments, especially the poultry manure + rabbit urine mixtures, also showed better performance, while the less fertilized or unfertilized treatments remained lower. Mineral analysis revealed enhanced calcium (206.13 ppm) and magnesium (250.83 ppm) under the 5 t/ha poultry manure with 2000 L/ha rabbit urine treatment in comparison with NPK fertilizer (135.96 and 123.53 ppm for calcium and magnesium, respectively). The study shows that organic fertilization improves okra fruit composition by stimulating bioactive metabolite synthesis and enhancing mineral nutrients, thus supporting sustainable production while improving the crop’s nutritional quality and overall value.