Reducing ammonia emissions from rice paddies: Modeling and field test of an alternative fertilizer

• In Korea agriculture is the main source of NH₃ emissions with health impacts • Lowland and upland fields emitted ∼62% and 38% of cropping NH₃, respectively • Urea fertilization caused 17–36% N loss as NH₃ in rice paddy systems • Ammonium sulfate fertilizer cuts NH₃ losses by more than two-thirds • Field evidence shows yield is preserved despite emission reduction Agriculture contributes >80% of global ammonia (NH₃) emissions, underscoring the challenge of mitigating NH₃ volatilization because of its association with a spectrum of deleterious environmental and public health ramifications. The source-specific mitigation strategies yet remain poorly constrained due to limited integration of emission inventories with field validation. In this study, we combined process-based CHANS modeling with field experimentation to quantify sectoral contributions to NH₃ emissions and evaluate fertilizer-based mitigation in Korean agriculture. Between 2001 and 2019, the agricultural sector contributed about 72-80% of total NH₃ emissions in Korea, with cropping systems contributing 12% (36% lowland and 64% upland) and livestock production representing the predominant source at 88%. Model analysis identified urea application in paddies was the predominant source of NH₃ emissions, prompting the hypothesis that substituting urea with ammonium sulfate could reduce NH₃ volatilization . A systematic field trial revealed rapid post-fertilization emissions, with NH₃ fluxes peaking immediately following fertilization and returning to background levels within 3–4 days regardless of the type of N fertilizer. In total, 15% and 49% of applied N were volatilized as NH₃ following urea applications at 45 and 90 kg N ha⁻¹, respectively. In contrast, emissions from ammonium sulfate were consistently < 22%. Importantly, rice yields were unaffected by fertilizer type. These findings indicate that replacing urea with ammonium sulfate can substantially mitigate NH₃ emissions without compromising productivity, offering a practical strategy for reducing agricultural ammonia losses.