Yield and nutritive value of the spring growth of an ageing timothy sward
Bibliographic record
Abstract
The decline in productivity of forage grasses with age since establishment has been recognised for several years, but this yield reduction and its consequences on nutritive value have not been studied in timothy (Phleum pratense L.). Our objective was to characterize the dry matter (DM) yield and nutritive value during spring growth of an ageing timothy sward grown under non-limiting N conditions. A timothy sward, seeded in 1998, was harvested at four developmental stages (stem elongation, early heading, late heading, and early flowering) during spring growth from 1999 to 2005. The average DM yield observed in production years 5, 6, and 7 was 43% of that measured in the first 4 production years when timothy was harvested at stem elongation or early heading, 52% when harvested at late heading, and 74% when harvested at early flowering. The yield potential of timothy during spring growth decreased with ageing at a rate of 0.66 and 0.91 Mg DM ha-1 yr-1 with harvests at early and late heading, respectively. The nutritive value of timothy harvested at stem elongation was greater in older (production years 5, 6, and 7) than in younger (first 4 production years) swards as indicated by in vitro true digestibility of DM (+ 48 g kg-1 DM), in vitro digestibility of NDF (+ 77 g kg-1 NDF), and neutral detergent fibre (NDF) concentration (-62 g kg-1 DM); this difference, explained mostly by the lower DM yield of older swards, disappeared when timothy was harvested later on in the growth cycle. Rates of change in nutritive value observed during the phase of reproductive development in spring growth were, therefore, greater in older than in younger swards. Our results demonstrate clearly the decline in timothy productivity with age and its consequences on nutritive value. Key words: Phleum pratense, harvesting year, stages of development, yield, digestibility
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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 | 0.000 |
| 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".