Spatiotemporally Matched Nitrogen Release from a Double Core-Shell Urea Improves Rice Growth

Photosynthetic efficiency and dry matter accumulation are essential for achieving high rice yields, yet conventional controlled-release fertilizers often fail to synchronize nitrogen (N) supply with crop demand. In this study, we evaluated a novel double core–shell controlled-release urea (DCSCRU) designed to align with the bimodal N uptake pattern of rice. A two-year field experiment was conducted to compare DCSCRU at three application rates (180, 225, and 270 kg N ha−1) with conventional urea and conventional controlled-release urea (both at 270 kg N ha−1). DCSCRU exhibited a distinct biphasic N release profile, with a rapid initial release peaking at 1.60% d −1 on day 10 to meet early vegetative demand, followed by a second peak (1.85% d−1 on day 45) supporting reproductive development. Compared with conventional urea, DCSCRU treatments significantly improved photosynthetic efficiency and dry matter accumulation during critical growth stages. The 270 kg N ha−1 DCSCRU treatment achieved a grain yield exceeding 11.50 × 103 kg ha−1, substantially higher than that of conventional urea. Notably, the 225 kg N ha−1 DCSCRU treatment produced a comparable yield (10.90 × 103 kg ha−1) to that of the conventional urea treatment (10.83 × 103 kg ha−1), indicating the potential to reduce N input by 16.7% without compromising yield. The enhanced physiological performance was attributed to improved N availability and optimized canopy function. These findings highlight DCSCRU as a promising strategy for high-yield, resource-efficient, and environmentally sustainable rice production.