Advancing the understanding and interpretation of plant and soil tests for phosphorus in Manitoba
Bibliographic record
Abstract
Selected factors proposed to be limiting the effectiveness of the assessment of plant and soil P status by current testing methods were studied, to provide information for use in improving the processes and interpretations. Growth and P status of field-grown spring wheat was monitored under a wide range of conditions. Plant P deficiency restricted growth early in the season, beginning one to two weeks after crop emergence, even where seed-placed P fertilizer was applied. However, within two to five weeks from emergence, shoot relative growth rates in the P-deficient treatments were at least as high as those in the high-P treatments. Plant analysis was most successful for predicting yield-limiting P deficiency if conducted during the first several weeks of growth. Determination of tissue total P concentration in the leaf or whole shoot, and of extractable inorganic leaf P concentration, could provide a good basis for assessing plant P status; comprehensive interpretive criteria were developed for each test. Leaf P concentrations generally declined until the stem extension stage, but shoot P concentrations declined throughout the growing season. For each test, concentrations tended to converge with time among sites and treatments. Examination of spatial variability of extractable P in four field soils revealed a high degree of variability over very short distances (1-2 cm), even where fertilizer had not recently been applied. Persistence of small localized zones high in P availability may enhance residual fertilizer P uptake by plants. Extractability of fertilizer residual P compounds by the Olsen NaHCO3 soil testing procedure was studied. Although the most highly soluble compounds dissolved rapidly, added octacalcium phosphate did not dissolve with soil present. Soil solutes, including Mg2+, Fe2+, and others, greatly retarded the dissolution. Octacalcium phosphate is an important P fertilizer reaction product in Manitoba soils and is moderately available to plants; its failure to dissolve may limit the effectiveness of the Olsen test in fully reflecting the residual availability of recently applied P fertilizer to crops. The simple solubility of a compound in a pure soil test extractant may not be a good indicator of the degree to which it will be recovered by the test in the presence of soil.
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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 | 0.003 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.003 |
| Science and technology studies | 0.002 | 0.002 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".