Decoupling between ammonia emission and crop production in China due to policy interventions

Cropland ammonia (NH₃ ) emission is a critical driver triggering haze pollution. Many agricultural policies were enforced in past four decades to improve nitrogen (N) use efficiency while maintaining crop yield. Inadvertent reductions of NH₃ emissions, which may be induced by such policies, are not well evaluated. Here, we quantify the China's cropland-NH₃ emission change from 1980 to 2050 and its response to policy interventions, using a data-driven model and a survey-based dataset of the fertilization scheme. Cropland-NH₃ emission in China doubled from 1.93 to 4.02 Tg NH₃ -N in period 1980-1996, and then decreased to 3.50 Tg NH₃ -N in 2017. The prevalence of four agricultural policies may avoid ~3.0 Tg NH₃ -N in 2017, mainly located in highly fertilized areas. Optimization of fertilizer management and food consumption could mitigate three-quarters of NH₃ emission in 2050 and lower NH₃ emission intensity (emission divided by crop production) close to the European Union and the United States. Our findings provide an evidence on the decoupling of cropland-NH₃ from crop production in China and suggest the need to achieve cropland-NH₃  mitigation while sustaining crop yields in other developing economies.