Nitrogen transformations and ammonia volatilization losses from <sup>15</sup>N-urea as affected by the co-application of composted pig manure
Bibliographic record
Abstract
Co-application of composted manure (compost) and urea is considered an environment-friendly fertilization practice; however, the high urease activity in compost may stimulate NH 3 volatilization and cause N loss from co-applied urea. To test the above hypothesis, we investigated the fate of urea co-applied with compost in a loam-textured soil through two laboratory incubation experiments. Urea (150 mg N kg -1 ) was co-applied with 0, 4.9, 9.8, and 14.6 g of compost (oven-dry basis) kg -1 of soil, designated as treatments UC0, UC1, UC2, and UC3, respectively. Co-application of compost and urea enhanced urea hydrolysis and increased the 1st order rate constant of urea hydrolysis from 0.047 h -1 in the UC0 to 0.139 h -1 in the UC3 treatments. Soil pH increased from 7.0 for UC0 to 7.6 for UC3, leading to greater NH 3 volatilization (up to two times more) in the soils receiving 9.8 g kg -1 or more of compost. Compost co-application also increased the immobilization of urea-derived N, probably because the organic matter added in compost stimulated microbial growth or NH 4 + fixation. Between 15 and 17% of urea-N was not recovered at the end of the incubation, but there was no difference in N loss among the treatments resulting from the contrasting effects (NH 3 volatilization vs. NH 4 + immobilization) of compost on N losses. Our results clearly show that application of compost with high urease activity increases NH 3 volatilization loss of N from the co-applied urea, but the total amount of N lost is also affected by immobilization of NH 4 + by the organic matter added to the soil through the applied compost. Key words: Ammonia volatilization, nitrogen dynamics, nitrogen-15 recovery, organic carbon, urease activity
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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 | 0.000 |
| Scholarly communication | 0.000 | 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 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".