Assessing organic phosphorus status of Cerrado oxisols (Brazil) using <sup>31</sup>P-NMR spectroscopy and phosphomonoesterase activity measurement
Bibliographic record
Abstract
Plant production in the Brazilian savannas, also known as the Cerrados, is limited mainly by low P availability in soils. Little is known about the P status in the Cerrados region, despite its increasing significance for the country’s agriculture. 31P-NMR spectroscopy of alkali extracts and phosphomonoesterase (PME) activity measurements were used to study forms of P and their stability in oxisols of natural and pasture systems. Total P content (Pt) in topsoils ranged from 301 to 456 mg kg-1 and organic P content (Po) from 84 to 194 mg kg-1 with the highest values under natural vegetation. The estimation of forms of soil P with different lability (provided by NaHCO3 and NaOH extractions) showed little difference between natural vegetation and pastures, but the proportions of Po extracted suggest the importance of organically bound P as a source of plant-available P. All NMR spectra showed signals of organic P (monoesters and diesters) and inorganic P forms (orthophosphate and pyrophosphate), with little influence of land use. Organic P appears to be mainly in the form of stable phosphomonoesters. The most marked effect of land use was a decrease in PME activity under recent pastures, indicating an increase of PME stability in topsoils after the maize-grass ley plantation. The importance of the pH of the PME activity measurement is also discussed. Key Words: Organic P, labile P, 31P-NMR, phosphosmonoesterase, Cerrado, Oxisols
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 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 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".