Ammonia emissions from urea fertilization – Multi-annual micrometeorological measurements across Germany
Bibliographic record
Abstract
Among the synthetic fertilizers used in crop production, the application of conventional urea is one of the major sources of ammonia (NH 3 ) emissions. However, NH 3 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 NH 3 emission (NH 3Ninput ) 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 NH 3Ninput was observed between fertilizer applications and regions, though NH 3Ninput tended to be higher at sites with higher sand contents than sites with higher clay contents. Rainfall was negatively correlated with NH 3Ninput , while N application rates had no effect. The current EFs overestimate the NH 3 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 NH 3 measurements across six agroecological regions in Germany. • Median N input related NH 3 Emission across Germany was 4.8 %. • Rainfall reduced NH₃ emissions, whereas increased sand content enhanced them. • No consistent trends or differences in NH 3 emissions between regions in Germany. • NH 3 Emissions in Germany were below current IPCC and EMEP emission factors for urea.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".