Ammonia emissions from urea fertilization – Multi-annual micrometeorological measurements across Germany

• Published in: Agriculture, ecosystems & environment Vol. 381; p. 109416
• Main Authors: Kemmann, B., Brokötter, J., Götze, H., Kelsch, A., Frößl, J., Riesch, S., Heinemann, P., Kukowski, S., Pacholski, A., Flessa, H.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2025
• Subjects: agriculture; agroecology; ammonia; Ammonia volatilization; clay; crop production; Emission factors (EFs); environment; fertilizers; Germany; IHF method; NH3 emissions; rain; sand; total nitrogen; Urea; Winter wheat; Germany; Urea; Ammonia volatilization; NH3 emissions; IHF method; Emission factors (EFs); Winter wheat
• ISSN: 0167-8809
• DOI: 10.1016/j.agee.2024.109416

Among the synthetic fertilizers used in crop production, the application of conventional urea is one of the major sources of ammonia (NH3) emissions. However, NH3 emission estimates based on existing emission factors (EFs) are subject to significant uncertainties due to limited underlying data, obtained under various conditions and applied methods. To assess the accuracy of current EFs for different regions within Germany, NH₃ emissions were measured using the integrated horizontal flux (IHF) method employing ALPHA passive samplers following urea application in 2021, 2022, and 2023 across six agroecological regions of Germany. Measurements were conducted under winter wheat cropping, with total nitrogen (N) rates of 145–230 kg N ha⁻¹ , split into two or three applications, resulting in 51 measurement campaigns. Measured N input related NH3 emission (NH3Ninput) ranged from 1.1 % to 20.7 % (median 4.8 %, mean 8.5 %), significantly lower than the 2019 IPCC (14.2 %) and 2023 EMEP (16.1 % for pH<7) estimates for urea. No consistent trend in NH3Ninput was observed between fertilizer applications and regions, though NH3Ninput tended to be higher at sites with higher sand contents than sites with higher clay contents. Rainfall was negatively correlated with NH3Ninput, while N application rates had no effect. The current EFs overestimate the NH3 emissions from urea applied to winter wheat under the conditions tested in Germany. The observed emissions may deviate from long-term regional trends due to inter-annual variability and complex environmental interactions. Nevertheless, establishing a national EF for Germany could enhance the accuracy of NH₃ emission estimates and improve assessments of mitigation measures' potential to reduce emissions. •Micrometeorological NH3 measurements across six agroecological regions in Germany.•Median N input related NH3 Emission across Germany was 4.8 %.•Rainfall reduced NH₃ emissions, whereas increased sand content enhanced them.•No consistent trends or differences in NH3 emissions between regions in Germany.•NH3 Emissions in Germany were below current IPCC and EMEP emission factors for urea.