Phosphorus diffusion from monocalcium phosphate co-applied with salts in a calcareous soil
Bibliographic record
Abstract
Mixing non-phosphatic salts with fertilizer P influences the solubility and mobility of P in soils. Little evidence, however, is available regarding the mechanisms causing such effects. The object ives of this study were to investigate the effects of mixing fertilizer P with (NH 4 ) 2 SO 4 , MgSO 4 or (NH 2 ) 2 CO on the diffusion of P in a calcareous soil (Gleyed Rego Black Chernozem), and to identify the causes for such effects. To the surface of 50-mm-long soil columns, maintained at field capacity water content, 32 P-labelled monocalcium phosphate (MCP) was applied alone or in combination with (NH 4 ) 2 SO 4 , MgSO 4 or (NH 2 ) 2 CO. Ratios of applied P:N, P:Mg and P:S were 1:5, 1:4.5 and 1:6, respectively. Extraction and analysis of each 2-mm layer of the columns after incubation for 1, 2, 3, and 4 wk revealed that the addition of (NH 4 ) 2 SO 4 and MgSO 4 with MCP significantly increased P diffusion whereas (NH 2 ) 2 CO had little or no effect. The mechanisms of such effects were identified using a multi-ionic, mechanistic, diffusion model. According to model predictions, the dissolution of MCP was increased by more than twofold when mixed with (NH 4 ) 2 SO 4 and MgSO 4 , and by 1.2-fold when mixed with urea. The main difference between SO 4 salts and urea in affecting P diffusion was the competition between the anion of the salt and P for precipitation with Ca. Sulphate competed strongly with P, reducing the precipitation of Ca phosphates. Application of urea increased soil pH initially, but eventually soil pH decreased with nitrification of NH 4 . Initial increase in pH to above 8.0 favoured precipitation of Ca phosphate, but the pH was not high enough to favour CaCO 3 precipitation. The application of P fertilizers with fertilizers containing SO 4 could be beneficial in calcareous soils due to enhancement of P solubility and mobility. Key words: Calcareous soils, phosphorus diffusion, precipitation, sulphate salts, transport model, urea
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| 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".