Nitrogen, Sulfur, and Oxygen Isotope Ratios of Animal‐ and Plant‐Based Organic Fertilizers Used in South Korea
Bibliographic record
Abstract
Organic fertilizers are increasingly used in agriculture in Asia and elsewhere. Tracer techniques are desirable to distinguish the fate of nutrients added to agroecosystems with organic fertilizers from those contained in synthetic fertilizers. Therefore, we determined the nitrogen, sulfur, and oxygen isotope ratios of nitrogen‐ and sulfur‐bearing compounds in animal‐ and plant‐based organic fertilizers (ABOF and PBOF, respectively) used in South Korea to evaluate whether they are isotopically distinct. The δ15N values of total and organic nitrogen for ABOF ranged from +7 to +19‰ and were higher than those of PBOF (generally <+6‰). This suggests that ABOFs have distinct δ15N values suitable for tracing these fertilizer compounds in the plant–soil–water system, whereas PBOFs have similar δ15N values to synthetic fertilizers. However, δ18O values for nitrate (δ18ONO3) from organic fertilizer samples (<+17.0‰) were consistently lower than those of synthetic nitrate‐containing fertilizers. The δ34S values of total sulfur, organic sulfur compounds (e.g., carbon‐bonded sulfur and hydriodic acid‐reducible sulfur), and sulfate for ABOFs yielded wide and overlapping ranges of +0.3 to +6.3, +0.9 to +7.2, and −2.6 to +14.2‰, whereas those for PBOFs varied from −3.4 to +7.7, +1.4 to +9.4, and −4.1 to +12.5‰, respectively, making it challenging to distinguish the fate of sulfur compounds from ABOF and PBOF in the environment using sulfur isotopes. We conclude that the δ15N values of ABOFs and the δ18ONO3 values of organic fertilizers are distinct from those of synthetic fertilizers and are a promising tool for tracing the fate of nutrients added by organic fertilizers to agroecosystems. Core Ideas Organic fertilizer is a potential contaminant in agroecosystems. Multi‐isotopes of animal‐ and plant‐based organic fertilizers were analyzed. Animal‐based organic fertilizer is discriminated from synthetic fertilizers by δ15N. Animal‐ and plant‐based organic fertilizers showed distinct δ18ONO3. The δ34S of animal‐ and plant‐based organic fertilizer is not reliable as a tracer.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 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 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".