Successful NH abatement policies and regulations in German agriculture.

Anthropogenic ammonia (NH) emissions, of which about 95 % are from agriculture, have led to environmental pollution, resulting in tremendous damage to human health and ecosystems. Thus, the NEC Directive 2016/2284/EU sets national reduction targets for NH emissions in individual EU countries. To implement the NEC Directive for NH emission targets, Germany amended the Fertilizer Application Ordinance in 2017 and 2020 (DüV_amended) and set the air pollution control regulation, Technical Instructions on Air Quality Control (TA_Luft). This study aimed to evaluate the impact of the DüV_amended on NH mitigation from applying livestock manure, digestates, synthetic nitrogen (N) fertilizers, and TA_Luft on housing and storage. This study showed that Germany reached the first national NH reduction target in 2020, as set by the NEC directive. The German DüV_amended, a significant policy change, has profoundly impacted NH emission mitigation from agriculture after 2017 by implementing measures aimed directly at NH reduction, reducing N surpluses, and improving N use efficiency. The reduction in NH emissions from synthetic N fertilizers between 2016 and 2022 contributed about 51 % to the decrease from the agricultural sector over the same period. Among the synthetic fertilizers, NH reduction from urea between 2016 and 2022 accounted for around 83 % of the total reduction from synthetic N, indicating that the NH emissions from urea fertilizer by reducing urea application and mandating urea to be incorporated immediately or to be stabilized with urease inhibitors played a crucial role in the sharp decrease in NH emissions over the last years in Germany. Achieving a high yield by lowering the synthetic N rate in this study strongly suggests that optimal reduction in N rate does not necessarily result in yield losses but rather in a pivotal relationship between the agronomic and environmental performance and indicates that the DüV_amended was an effective measure that can reduce the NH emissions. Over 80 % of Germany's annual agricultural NH emissions in 2021 and 2022 originated from livestock and digestates from energy crops. Mandatory close to the soil band application of slurry and digestates on cultivated cropland since 2020 reduced NH emissions. In addition, banning of broadcast application of slurry to grassland and manure incorporation within one hour on uncultivated soils will become mandatory in 2025 to comply with NEC 2030´s target of 29 % NH reduction relative to 2005. The recent German air pollution control regulation (TA_Luft) enforces abatement measures such as air purifiers in large poultry and pig housings and covered storage of slurry and digestate storages of large farms. The results of the German NH abatement strategy for synthetic N fertilizers may help reduce NH emissions worldwide, especially for countries consuming high amounts of urea fertilizers.