Improved Estimates of Ammonia Emissions from Global Croplands

Reducing ammonia (NH 3 ) volatilization from croplands while satisfying food demand is strategically required to mitigate haze pollution.However, the global pattern of NH 3 volatilization remains uncertain, primarily due to the episodic nature of NH 3 volatilization rates and the high variation of fertilization practices.Here, we improve a global estimate of crop-specific NH 3 emissions at a high spatial resolution, using an updated data-driven model with a survey-based dataset of fertilization scheme.Our estimate of globally-averaged volatilization rate (12.6% ± 2.1%) is in line with previous data-driven studies (13.3% ± 3.1%), but results in one quarter lower emissions than process-based models (16.5% ± 3.1%).The associated global emissions are estimated at 14.4 ± 2.3 Tg N, with more than 50% of the total stemming from three stable crops or 12.2% of global harvested areas.Nearly three quarters of global cropland-NH 3 emissions could be reduced by improving fertilization schemes (right rate, right type, and right placement).A small proportion (20%) of global harvested areas, primarily located in China, India, and Pakistan, accounts for 64% of abatement potentials.Our findings provide a critical reference guide for future abatement strategy design when considering locations and crop types.