Sorption and desorption of phosphorus as influenced by corn stalk residue, pH, and ionic strength in a gleysol from Québec, Canada
Bibliographic record
Abstract
The Pike River watershed has a history of phosphorus (P) pollution due to surface and subsurface leaching, and erosion of agricultural soil rich in P. It is therefore important to consider factors that may change the dynamics of P sorption and desorption behaviours and potentially increase the P concentration in the soil solution.This thesis investigates the effect of corn stalk residue presence and application rate on P sorption and desorption.This thesis also investigates the effect of varying solution pH and ionic strength on P release.Batch experiments were used to investigate P sorption followed by experiments to test the reversibility of the sorption process under different corn stalk residue applications (0.3,5.3,10.3,15.3, and 20.3%) and at different P concentrations (0, 12.9, 27.7, 42.2, 57.0, and 71.8 mg L -1 ).The quantity of P sorbed to soil was found to decrease significantly as residue application rates increased (p<0.0001).Phosphorus remaining in the soil after desorption decreased significantly as application of residues increased (p<0.0001).Varying the P concentration under a constant dosage of residue (5.3%) showed that the concentration of P sorbed increased with increases in P application; however sorption efficiency decreased with increasing P application.Sorption in the presence of residues was significantly lower (p<0.0001)than sorption in the absence of residues for P treatments higher than 42.2 mg L -1 .Percent sorbed P remaining after desorption was similar in the presence (85-91%) and absence (86-91%) of the 5.3% corn stalk residue treatment.A second study was performed to investigate the effect of varying ionic strength and pH on P release into solution and to identify which factor had a greater effect on P release.It was found that at low ionic strengths the pH effects on P release were more pronounced whereas at high ionic strengths the P concentrations were not significantly different regardless of pH level.Since residue incorporatio n increased the availability of P in this soil, then due to the P pollution history of the area it is suggested that a large scale study be conducted taking into account a temporal component I would like to acknowledge the contributions of:• My supervisor Dr. Zhiming Qi in the design and revision of this work.• Dr. Eman M. ElSayed in the design and revision of chapter 3 of this thesis.I would like to thank:• My supervisor Dr. Zhiming Qi for his patience
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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 | 0.003 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".