Soil Test Phosphorus and Phosphorus Fractions with Long‐Term Phosphorus Addition and Depletion
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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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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.001 |
| Science and technology studies | 0.001 | 0.004 |
| Scholarly communication | 0.000 | 0.001 |
| 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 it