Fertilizer Source Influenced Nitrous Oxide Emissions from a Clay Soil under Corn
Bibliographic record
Abstract
Synthetic N fertilizers are a major source of N 2 O emissions from soil. A field experiment was conducted during three growing seasons (2004–2006) on a clay soil (fine, mixed, frigid Typic Humaquept) under corn ( Zea mays L.) to evaluate the impact of N fertilizer source and application rate on N 2 O emissions. Treatments consisted of three sources of N fertilizer (urea–NH 4 NO 3 32% [UAN], Ca–NH 4 NO 3 [CAN], and aqua NH 3 [AA]) at four different rates (0, 100, 150, and 200 kg N ha −1 ). Fertilizers were banded 5 cm below the soil surface between corn rows at the six‐leaf stage and N 2 O emissions were measured weekly. For all 3 yr of this study, cumulative N 2 O emission decreased in the order UAN ≥ CAN ≥ AA. Averaged across years, fertilizer‐induced post‐sidedress emissions were greater than the Intergovernmental Panel on Climate Change default factor (0.01 kg N 2 O‐N kg −1 N), with values of 0.038, 0.033, and 0.027 kg N 2 O‐N kg −1 N for UAN, CAN, and AA, respectively. The N 2 O emissions increased linearly with N rate, even at rates exceeding the optimum level for grain yield. Peaks of N 2 O flux occurred on the days following fertilizer application and in early fall when the soil was re‐wetted. Emissions of N 2 O were higher at water‐filled pore space >0.57 m 3 m −3 and were also related to soil inorganic N and water‐extractable organic C contents. Our results confirm that N fertilizer source and application rate can impact N 2 O emissions but these effects are modulated by soil environmental conditions.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 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 | 0.001 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 teacher head, 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".