Fertilization is a vital component of modern agriculture to support plant growth and productivity. However, inefficient and excessive fertilization practices can degrade soil quality and cause environmental pollution. This study aims to design and develop an automatic fertilization system based on the Internet of Things (IoT), integrated with Nitrogen, Phosphorus, and Potassium (NPK) sensors and fuzzy logic as an intelligent control mechanism. The system is designed to detect macro-nutrient content in the soil in real-time and automatically adjust the dosage and timing of fertilization according to actual field conditions. Sensor data is transmitted wirelessly to a cloud platform for processing, while fuzzy logic is utilized to flexibly determine fertilizer application tailored to the plant’s needs. The research methodology involves hardware design, software development, and system testing in a simulated field environment. Preliminary results indicate that the system can improve fertilization efficiency by up to 30% compared to manual methods and reduce the frequency of misapplied fertilizers. This research is expected to Offer an innovative solution toward realizing smart and sustainable agriculture.