<p>Inefficient nitrogen (N) management in agriculture results in significant environmental pollution through nutrient leaching and greenhouse gas emissions. We propose a dynamic soil-N-based (DSNB) fertilization approach, demonstrating a novel implementation of an automated, closed-loop N-fertilization system in soil-based cultivation. The DSNB system utilizes real-time soil nitrate (NO₃⁻) monitoring to continuously adjust N application, maintaining defined concentration ranges to effectively synchronize N supply with dynamic plant N demand. We compared DSNB fertilization against predetermined fertilization guidelines in parallel-group randomized trials across two representative vegetable crops: lettuce in a 24-unit lysimeter system and bell pepper in a 12-plot field trial. Our results demonstrated that DSNB fertilization maintained soil NO₃⁻ concentrations within a defined range, in contrast to predetermined fertilization that led to either N surplus or deficiency. The DSNB fertilization resulted in a substantial increase in N use efficiency and a major reduction in NO₃⁻ leaching and soil gaseous N emissions. A broader analysis of the U.S. vegetable production sector found that, on average, farmers applied ~25% more N than recommended, representing a significant surplus that could be mitigated by adopting DSNB fertilization. This study demonstrates that the DSNB fertilization provides a crucial pathway for improving N management and reducing environmental pollution.</p><p></p>