Bell pepper (Capsicum annuum L.) is one of the most important greenhouse vegetables. Use of seedlings is a common production method for bell pepper in most greenhouses, thus seedling quality affects yield. Today, the use of biological fertilizers to replace chemical fertilizers in the production of agricultural products has become important. The present study was conducted to investigate the effect of chemical fertilizers and bio-fertilizers (Nitrokara and Phosphonitrokara) on some seedling characteristics of the bell pepper. The study investigated how different fertilizer combinations and timing affect pepper seedling production. The first experiment tested the 20N:20P:20K fertilizer, the second tested 10N:45P:10K, both at different application timing. The third experiment examined the impact of biological fertilizers (Nitrokara and Phosphonitrokara) combined with 20N:20P:20K on the seedling growth. All experiments were carried out using commercial bell pepper cultivars Inspiration, Arancia, and Tarento. A fertilization regime of 2 g/L 20N:20P:20K, applied every three days, improved yield-related traits and the physiological quality of the bell pepper, regardless of the type of cultivar. Balanced mineral fertilizers, particularly 2 g L-1 of 20N:20P:20K applied every three days, significantly enhanced plant height, root and shoot fresh and dry weight, root volume, leaf area, stem diameter, and chlorophyll index across cultivars. Finally, cultivar Inspiration indicated more responsive to balanced NPK, showing high shoot biomass gains, while cultivar Arancia showed a clear trade-off; balanced NPK favored shoots, while high phosphorus fertilizer enhanced roots. Similar pattern to Arancia, cultivar Tarento with balanced NPK boosting canopy/photosynthesis and high phosphorus fertilizer improving roots and height. Finally, balanced 20:20:20 fertilizer is optimal for maximizing aboveground productivity and photosynthetic efficiency, while high phosphorus 10:45:10 shifts biomass allocation toward roots, potentially useful for stress adaptation or soil exploration.
