Differentiated strategies for synergistic mitigation of ammonia and methane emissions from agricultural cropping systems in China

Abstract

Ammonia (NH3) and methane (CH4) emissions from agricultural cropping systems in China have substantially impacted environmental quality and climate change, which become the key sector for synergizing pollution control and carbon reduction. However, the experiences of synergistic NH3 and CH4 emission governance at fine scales in this sector are still lacking. Here, we estimated NH3 and CH4 emissions from agricultural cropping systems in China in 2019 and identified regional characteristics of these emissions using advanced spatial analysis techniques. Subsequently, we developed an innovative synergistic mitigation zoning identification method to establish targeted and spatially differentiated reduction measures, addressing a critical gap in mitigation strategies for agricultural cropping systems in China. The results showed that NH3 and CH4 emissions from the three most important crops were 3.04 Tg N yr-1 and 8.13 Tg C yr-1, respectively. NH3 and CH4 emissions exhibited the highest values in Eastern China, but the highest emission densities of NH3 (49.8 kg N ha-1 yr-1) and CH4 (394 kg C ha-1 yr-1) were observed in Northwest and South China, respectively. Further, bivariate local indicators of spatial association (LISA) maps revealed that the middle and lower reaches of the Yangtze River were hotspots for simultaneous high emissions of NH3 and CH4. Finally, based on the identified eight categories of zones, region-specific mitigation measures were proposed, including improved fertilization practices, irrigation methods, and straw management. These targeted, spatially differentiated mitigation strategies provide a reference framework and feasible approach for synergistic pollution control and carbon reduction in China's agricultural sector.