Evaluation of six phosphorus extraction methods for compliance testing of recycled P fertilizers
Bibliographic record
Abstract
Phosphorus (P) recycling for fertilizer production addresses the dependency on phosphate rock and mitigates P losses to the environment. However, predicting plant-available P in recycled fertilizers is challenging due to their diverse chemical composition. This study aimed at identifying the most suitable P extraction method for fertilizer compliance testing, considering their correlation with actual fertilization efficiency, as well as their simplicity, throughput, recognition and cost. Studies on fertilizer P compliance testing often lack recommendations on minimum P extractability threshold values. Here, thresholds are calculated based on actual fertilization efficiency of a large, chemically diverse set of recycled P fertilizers, many of which are already marketed. Thirty recycled P fertilizers were extracted with H 2 O, neutral ammonium citrate (NAC), electro-ultrafiltration (EUF), ferrihydrite-filled membranes (iron bag; IB), sodium bicarbonate (NaHCO 3 ) and diffusive gradients in thin films (DGT). The mineral replacement value (MRV) of the fertilizer set was previously evaluated in three pot experiments at a fertilization rate of 50 mg kg −1 soil. MRV correlations with the extractions methods showed similar results for all besides H 2 O, which cannot be a reliable indicator for P availability. Fertilizers were classified as efficient or inefficient based on their MRV exceeding or falling below 60 % of the triple superphosphate reference value. The minimum P extractability threshold value (MPETV) for each method was based on the efficiency classification and it minimized the number of misclassified fertilizers. NAC, with a 60 % extractable minimum P threshold value, was the most adequate method for compliance testing, despite its overestimation of iron phosphate availability. • H 2 O extraction of P fertilizers does not reflect P uptake by plants. • A common P extractability threshold value is recommended for all fertilizers. • NAC overestimates the availability of iron phosphate fertilizers. • NaHCO 3 underestimates the availability of less soluble calcium phosphates. • Minimum NAC 60 % P t extractability is recommended for compliance testing in the EU.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.005 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 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".