Long-Term Changes in Mehlich-3-Extractable Sulfur and Magnesium under Intensive Agriculture in Eastern Canada
Bibliographic record
Abstract
Leachable nutrients such as sulfur (S) and magnesium (Mg) may become limiting under temperate regions with sandy soils. This long-term georeferenced study assessed changes in Mehlich-3-extractable S and Mg in the province of Prince Edward Island (PEI), Canada. The Island was sampled over 3 years (one cycle, over 500 sampling points) from 1998 to 2015 for a total of six cycles. Regression kriging was used as a method of interpolation. Sulfur in the high category (>25 mg kg−1) dominated during the first two cycles (69%–98% of the total area) and then decreased below 1% of the total area during the last two cycles. The area in the low to medium category (7–18.50 mg kg−1) represented less than 1% of the total area in the first three cycles and increased to 84% in the last cycle. Magnesium distribution was dominated by soils within the low to medium range (36–116 mg kg−1), representing 74% to 97% of the total area from cycle 1 to cycle 6, respectively. Areas within the Mg range of 116 to 196 mg kg−1 changed from 24% of the total area in cycle 1 to 3% of the total area by the end of cycle 6. The S and Mg contents were positively correlated to soil organic carbon and negatively correlated to phosphorus. In a temperate climate and sandy loam soils, S and Mg decline over time under intensive cultivation, and the soil supply alone may not meet the crop S and Mg requirements.Abbreviations: Al: aluminum; C: carbon; CEC: cation-exchange capacity; CV: coefficient of variation; DEM: digital elevation model; Fe: iron; GIS: geographic information system; GPS: Global Positioning System; K: potassium; Mg: magnesium (extracted by Mehlich-3 solution); N: nitrogen; OK: ordinary kriging; P: phosphorus; PEI: Prince Edward Island; RK: regression kriging; RMSE: root mean square error; S: sulfur (extracted by Mehlich-3 solution); SOC: soil organic carbon; SOM: Soil Organic Matter.
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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 | 0.003 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".