Effect of soil sample handling and storage on inorganic nitrogen determination: Implications for the presidedress nitrate test
Bibliographic record
Abstract
Abstract The presidedress nitrate test (PSNT) is a nitrogen (N) fertilizer decision support system (DSS) that uses soil test nitrate (NO 3 − ) to provide an N rate recommendation for corn. We studied the effect of soil sample storage and handling on soil test NO 3 − , ammonium (NH 4 + ), and the N rate recommended by the PSNT. Soils from 35 agricultural fields located in southern Ontario, Canada, were collected in June and July and underwent two soil storage treatments and four soil handling treatments. Soils were either handled immediately or frozen (−15°C) for 3 months before handling. Soil handling included (1) immediate extraction in a moist state or oven‐drying for 24 h at (2) 35°C, (3) 65°C, or (4) 105°C. Samples were extracted with a 2.0 M KCl solution for inorganic N determination and immediate, fresh‐extracted samples served as baseline soil test values. Ammonium‐N was increased by freezing and drying at any temperature, while NO 3 − test values were significantly affected by freezing only. However, oven‐drying samples changed PSNT DSS N rate recommendations in 34%–43% of location‐years when handled immediately and 51%–68% of samples when initially frozen, depending on drying temperature. Most of these deviations were underapplications and relatively small when handled immediately (20 kg N ha −1 ) or frozen (37 kg N ha −1 ). We conclude that PSNT samples should not be frozen and that oven‐drying often alters PSNT‐based N rate recommendations.
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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 | 0.008 | 0.016 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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 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".