Controlled-Release Urea Coordinates Maize Physiology with Soil Nitrogen Retention: Balancing High Yield and Environmental Sustainability

Controlled-release urea (CRU) offers potential for improving nitrogen use efficiency (NUE) in intensive maize systems, but comprehensive evaluations of its agronomic, physiological, and environmental impacts remain limited. Through a two-year field experiment in the North China Plain comparing three CRU types (polymer/sulfur-coated PSCU, thermosetting polymer-coated TCU, and polymer-coated PCU) with conventional urea at five N rates (0-280 kg N ha–1), we demonstrate that CRU at 180 kg N ha–1 maintained high maize yields (13.9 Mg ha–1) while reducing N inputs by 12-19% and improving NUE by 37.6%, with TCU showing superior performance. The significant increase in Pn by 7.9–32.7% and Ci by 20.6–40.0% under CRU during the silking and milking stages. The CRU treatments also sustained optimal levels of hormones, N metabolism enzymes, sucrase and urease activities. Compared to common urea, life cycle assessment indicates that CRU has achieved a 47.5% reduction in reactive nitrogen losses, primarily due to lower ammonia volatilization and nitrate leaching. Additionally, when compared to common urea, CRU has resulted in a 18.7% decrease in greenhouse gas emissions. Economically, CRU outperformed common urea, with TCU providing the highest net benefit through yield stability and labor savings. These findings establish TCU at 180 kg N ha–1 as an optimal strategy for sustainable intensification of maize production in the NCP, balancing productivity, profitability and environmental protection.