Fertilization plays a crucial role in meeting the nutrient requirements of plants to achieve optimal production. The application of controlled-release fertilizer (CRF) on red onion cultivation holds the potential to enhance fertilizer efficiency while reducing water pollution. This study aimed to investigate the impact of CRF application on the availability of essential nutrients of P, S, Fe, Cu, Zn, Mn, and production of red onion (Allium ascalonicum L.). The research was conducted in two stages, an incubation experiment in laboratories and field experiments. The treatments included three types of fertilizers, P1: NPKCaMgS (13-8-10-5-9-2), P2: NPKS (19-12-15-4), and Mutiara: NPK (16-16-16). For the incubation experiment, two fertilizer doses were used: D6 (600 kg/ha), D12 (1200 kg/ha), along with a control group. For the field experiments, four fertilizer doses were employed: D3 (300 kg/ha), D6 (600 kg/ha), D9 (900 kg/ha), D12 (1200 kg/ha), also with a control group. The results indicated that the availability of P, Cu, and Mn increased with a longer incubation period, while the availability of Fe and Zn decreased over time. The availability of S exhibited irregular patterns with an extended incubation period. Notably, the highest onion production was achieved using NPKCaMgS ((13-8-10-5-9-2) at a dose of 300 kg/ha.