Rice productivity faces critical sustainability challenges from stagnating yields and inefficient fertilizer use, particularly in intensive agricultural regions like the Yangtze River Delta (YRD) of China. Controlled-release blended fertilizers (CRBF), which synchronize nutrient release with crop demand, represent a promising strategy to enhance rice productivity. Here, we conducted an eight-year (2017–2024) field study across 25 representative sites in the YRD to evaluate CRBF’s effects, complemented by a regional extrapolation analysis. Our findings showed that, relative to conventional fertilization, CRBF increased rice yield by 4.9%, primarily by increasing the number of effective panicles (5%) and plant biomass (5.2%–11.3%). Notably, this yield benefit rose to 5.3% when CRBF was applied via deep placement, which was attributed to greater root biomass (13.1%–29.2%) and higher soil NH₄⁺-N availability (24.3%–43.6%), thereby enhancing N uptake. Furthermore, initial soil organic matter was identified as the predominant modulator of CRBF effectiveness. Regional extrapolation projected that applying CRBF could enhance rice yield by 4.0% across the YRD, with deep placement providing an additional 2.1% gain. In conclusion, our study demonstrates that adopting CRBF, particularly with deep placement, is a robust and effective strategy to sustainably boost rice productivity in intensive rice cultivation systems.