Controlled-release urea enhances nitrogen fertilizer use efficiency by synchronizing soil nitrogen supply with...

Effective nitrogen management is essential for regulating nutrient uptake and improving productivity in oilseed rape (Brassica napus L.). However, mismatches between soil nitrogen availability and crop demand often limit nitrogen use efficiency (NUE). A two-year field experiment was conducted to compare nitrogen application strategies, including controlled-release urea (CRU), single-application urea (OU), split-application urea (TU), and treatments with a 25% reduction in nitrogen. The study evaluated their effects on soil inorganic nitrogen dynamics, biomass accumulation, nutrient uptake, yield components, and nitrogen use efficiency. The results showed that nitrogen release pattern strongly influenced soil nitrogen availability and crop performance. Both controlled-release urea and split-application enhanced biomass accumulation, nutrient uptake, and yield components compared with single-application urea. At an application rate of 240 kg N ha^-1, overwintering dry matter increased by 19.9-28.2% in 2023 and 14.6-17.0% in 2024. Nitrogen accumulation increased by 17.6-32.0% in 2023 and 31.6-33.9% in 2024 under CRU240 and TU240 compared with OU240. Grain nitrogen accumulation showed even greater increases, reaching 115.7-149.3% in 2023 and 52.1-52.7% in 2024. Pod number also increased (18.7-19.4% in 2023 and 24.8-27.7% in 2024), along with nitrogen partial factor productivity (by 27.1-60.8%) and nitrogen recovery efficiency (by 16.0-25.7%) relative to OU. Additionally, CRU maintained higher levels of soil NH₄ ⁺-N and NO₃ ^--N during the vegetative growth stage. A 25% reduction in nitrogen input decreased biomass and nutrient accumulation by 12-50%, although CRU180 and TU180 partially mitigated these reductions. Optimizing the timing of nitrogen release improves the synchronization between soil nitrogen supply and crop demand. Controlled-release urea performs comparably to split application while requiring fewer fertilizer applications. It also enhances the coordination of nutrient uptake, biomass accumulation, and nitrogen use efficiency, even under reduced nitrogen input. In conclusion, the reduced one-time application of controlled-release urea improved nutrient uptake coordination, nitrogen use efficiency, and crop productivity, indicating its potential as an effective nitrogen management strategy for winter oilseed rape production in the study region.