Optimizing rice productivity using controlled-release blended fertilizers in the Yangtze River Delta of China

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.