Soil Test Phosphorus and Phosphorus Fractions with Long‐Term Phosphorus Addition and Depletion
Bibliographic record
Abstract
The fate of fertilizer P in soil during crop production has to be determined to evaluate the long‐term economic value and sustainability of fertilizer practices. We assessed changes in soil test P and soil P fractions with continuous P fertilization and soil P depletion under continuous corn ( Zea mays L.) in a Ste. Rosalie clay soil (humic Gleysol; fine, mixed, frigid, Typic Humaquept). Soil samples were analyzed for Mehlich‐3 P (M‐3 P) and P fractions using a modified Hedley's procedure. Soil M‐3 P values remained constant in spite of crop removal in soil not receiving fertilizer for 10 yr. Continuous P fertilization at rates from 44 to 132 P ha −1 yr −1 increased linearly soil M‐3 P, with 6.3 kg P ha −1 of net P addition required to increase M‐3 P by 1 mg P kg −1 Residual fertilizer P in soil resulted from the continuous P addition were found predominately in labile inorganic P (LP i ) (NaHCO 3 –P i ) and moderately labile P i (MLP i ) (NaOH‐P i ). Increased P rates favored soil P transformation from LP i to MLP i , indicating enhanced soil P retention. With P depletion, soil M‐3 P declined in plots previously receiving 132 kg P ha −1 yr −1 , with 4.2 kg P ha −1 crop P removal decreasing soil M‐3 P by 1 mg P kg −1 Continuous crop removal of soil residual P (Res‐P) resulted in decreases in soil LP i and increases in MLP i , an indication of increased retention of Res‐P with time. However, moderately stable P i (HCl‐P i ) remained constant, both with continuous P addition and P depletion. Conversion of residual fertilizer P to less available P forms in soil was a slow process and thus the fate of the Res‐P should be taken into consideration when developing soil nutrient management plans.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".