Controlled‐release nitrogen application mitigated soil ammonia volatilization without compromising crop yields: a case study in Sichuan Basin paddy soil

Abstract Basal application of controlled‐release urea (CRU) combined with conventional urea has been proposed to better match the temporal nitrogen (N) demand of crops, reducing fertilization costs and offering greater practical applicability. Ammonia (NH3) volatilization is considered a major pathway of N loss in paddy, yet its response to CRU remains unclear. To evaluate the effects of partially substituting urea with CRU on NH3 volatilization and agronomic performance, field experiments were conducted in rice (Oryza sativa L.)–wheat (Triticum aestivum L.) and rice–rapeseed (Brassica napus L.) rotation with different CRU substitution rates (0%, 10%, 20%, 40%, 80%, and 100%). Results showed that the 40%–100% CRU treatments effectively decreased surface water NH4+‐N content and cumulative NH3 volatilization compared to other fertilization treatments. In particular, compared with other treatments, the 40% CRU treatment significantly reduced the ratio of cumulative NH3 volatilization to total N input to 8.4% in the rice–wheat rotation. In the rice–rapeseed rotation, the 40% CRU treatment increased grain yield, partial factor productivity of nitrogen, and apparent N‐fertilizer utilization efficiency. In the rice–wheat rotation, the 40% CRU treatment produced the tallest rice plants (52.71 cm), while in the rice–rapeseed rotation, it achieved the highest growth rate (25.97 kg hm−2 day−1). Their results demonstrate that replacing 40% of urea with CRU could effectively reduce NH3 volatilization while simultaneously enhancing rice N accumulation and agronomic performance, particularly in rice–wheat rotation system in the Chengdu Plain.