The delta yield procedure for nitrogen fertilisation of maize in South Africa
Bibliographic record
Abstract
The nitrogen fertilisation requirement for maize in South Africa is generaly estimated through the optimum yield-nitrogen rate procedure. The efficacy of this procedure is questionable. Delta yield, the difference between the maize grain yield at the economic optimum and that of a zero nitrogen fertilised control, was investigated for its ability to estimate the economically optimum nitrogen fertilisation rate for the South African maize producing area. Data from 124 locality-year fertilisation trials scattered over this area were used for the analyses. As in North America, optimum nitrogen rate correlated better with delta yield (R2 = 0.66) than with optimum yield (R2 = 0.51). Consequently, it shows potential to be a trustworthier predictor of the nitrogen fertilisation requirement of maize than the traditional optimum yield-nitrogen rate procedure. The delta yield model (Y = X0.602 where Y is the amount of fertiliser nitrogen and X delta yield, both measured in kg ha−1) was not only uniform for different soil and climatic regions in South Africa, but appears to be similar to that found for five states of the USA.
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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 | 0.003 | 0.005 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".