Phosphorus and Nitrogen Relationships during Spring Growth of an Aging Timothy Sward
Bibliographic record
Abstract
Plant‐based methods of determining P and N deficiencies require critical concentration values. We studied the response of timothy ( Phleum pratense L.) to P and N fertilization over 7 yr with the objective of using relationships between P and N concentrations and dry matter (DM) yield to determine critical P and N concentrations. Timothy, seeded in 1998, was harvested during spring growth from 1999 to 2005 in an experiment with four sampling dates (stem elongation, early heading, late heading, and early flowering), four P applications (0, 15, 30, and 45 kg P ha −1 ), and four N applications (0, 60, 120, and 180 kg N ha −1 ). Maximum DM yield and, therefore, nonlimiting P and N conditions, were obtained with 120 kg N ha −1 without applied P. Under these nonlimiting conditions, relationships between P and N concentrations and DM yield changed with production years. Critical N concentration (N c ) in older swards (>4 yr; N c = 37.0 × SB −0.35 ; R 2 = 0.79), expressed as a function of shoot biomass (SB), was less than previous reports on younger swards (N c = 48.0 × SB −0.32 ). Critical P concentration (P c ) was also less in older swards (P c = 3.27 × SB −0.20 ; R 2 = 0.68) than in younger ones (P c = 5.23 × SB −0.40 ; R 2 = 0.63). Critical P concentration can also be expressed as a function of N concentration (P c = 1.07 + 0.063N; R 2 = 0.71), a relationship independent of sward age and shoot biomass but affected by N deficiency; the slope is the same but intercept values vary from 1.31 to 1.41 when N limits shoot growth. Critical P and N concentrations can then be used to quantify the degree of P and N deficiency in young and old timothy swards.
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How this classification was reachedexpand
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 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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 teacher head, 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".