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.