Comparison of different phosphorus extraction and determination methods using manured soils
Bibliographic record
Abstract
Soil test P (STP) methods were developed for fertilizer P recommendation in crop production. As soil P content of arable land increases due to manure application, the suitability of these STP methods for assessing P runoff potential from a field needs to be evaluated. The objective of this research was to evaluate various P extraction and determination methods using manured soils for their potential use as environmental P testing methods. Eighty one soil samples were taken in 1998 from various manured fields and research plots across Alberta. Phosphorus in the samples was extracted using deionized water, Miller-Axley (0.03 M NH4F + 0.015 M H2SO4), modified Kelowna (0.015 M NH4F + 0.25 M NH4OAc), and Mehlich 3 (M3) (1.5 M NH4F + 0.1 M EDTA) procedures. Phosphorus concentration in all extraction solutions was determined by the molybdenum blue colorimetric method in a Technicon II autoanalyzer. In addition, P content of the deionized water and M3 extractions was determined by an inductively coupled plasma emission spectroscopy (ICP) method. Soluble organic carbon content was measured in the deionized water extraction. The extractable P concentration increased as the acidity of the extraction solution increased in the order: M3 > modified Kelowna > Miller-Alxey > deionized water. The P extracted by Miller-Axley and M3 was strongly related to the deionized water extractable P, suggesting that both methods may be useful in assessing potential P runoff from arable land. The P concentration by the ICP determination was much higher than with the colorimetric method in M3 and the deionized water. The P concentration difference between the two determination methods was largely correlated to the soluble organic carbon in the deionized water extraction (r = 0.828***), suggesting that the undetected P by the molybdenum blue colorimetric method may exist in organic forms. To asses P runoff risk from arable land, both soluble inorganic and organic P need to be considered, and the ICP method can determine the total P, which includes both. In developing a STP for environmental soil P management, both P extraction and P determination methods should be standardized, and our results suggest that M3 and Miller-Axley extraction, and ICP determination are suitable methods for assessing P runoff. Key words: Soil test P, colorimetric P, ICP-P, dissolved organic carbon, soluble organic P, manure application rate
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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 | 0.001 | 0.003 |
| 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 | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 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".