Binding of inorganic sulphate and phosphate in humid-climate soils measured using column leaching, equilibration and extraction methods
Bibliographic record
Abstract
The ability of soil samples to bind applications of inorganic sulphate and phosphate was examined in the laboratory using column leaching, solution equilibration and extraction methods. Eleven soil samples from the Fraser Valley of British Columbia with a range of soil characteristics and management histories were examined. Column leaching trials showed that sulphate was bound to soils, but not as strongly as phosphate. There was no evidence of significant sulphate binding during the equilibration trials but there was substantial native sulphate bound by the soils as shown by extraction of significant sulphate concentrations by bicarbonate extraction following equilibration. This shows that sulphate is not bound according to the traditional theory of adsorption, but other undefined mechanisms are involved. Both column leaching and equilibration results showed that the samples studied varied considerably in their native phosphate retention attributes, with some samples releasing no phosphate and others releasing considerable phosphate into the water treatments. Equilibration trials showed that some of the soils bound large quantities of phosphate resulting in no phosphate in the soil solution whereas others bound much less resulting in significant phosphate concentrations in the soil solution. Phosphate binding followed the Freundlich equation in eight of the samples, the Tempkin equation in one sample and a direct linear relationship in two samples. The Langmuir equation fitted most of the samples that had followed Freundlich equation reasonably well, but did not fit the other samples. This showed that determination of the maximum amount of phosphate that can be bound by the sample (i.e., P saturation) using the Langmuir equation cannot be used for all humid-climate soils of British Columbia. Two alternate direct measurements are proposed to determine the potential risk of phosphate in soils to contaminate water: amount of phosphate released during equilibration with water (native unbound phosphate) and amount of phosphate bound during equilibration with a low (approximately 25 mg P kg-1) phosphate solution (potential for the soil to bind applied P). These results show that sulphate and phosphate binding mechanisms by coastal British Columbia soils are not well understood. The nature of the binding mechanisms needs to be determined to develop and interpret soil analyses for agronomic and environmental purposes. Key words: Sulphate binding, phosphate binding, P saturation, soil solution P
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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 | 0.001 |
| 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 | 0.001 | 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 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".