Controlled-release urea for winter wheat in southern Alberta
Bibliographic record
Abstract
The recent development of low-cost controlled-release urea (CRU) may provide additional options for N fertilization of winter wheat (Triticum aestivum L.). Two field experiments were conducted over 3 yr at three locations in southern Alberta to evaluate different options of applying CRU to winter wheat. In the first experiment, three N fertilizers (20-day CRU, 40-day CRU and urea) were seed-placed and side-banded at the time of seeding at 0, 30, 60, 90 and 120 kg N ha -1 . Stand densities were substantially reduced by seedrow application of urea at rates greater than 30 kg N ha -1 , but were unaffected by seedrow application of CRU, even at the highest rate of N application. When N fertilizer was sidebanded, stand densities were unaffected by fertilizer type or N rate. Yield gains due to N application were reduced by application of high rates of seed-placed urea, but similar for other treatments. Grain protein concentration and N uptake were also similar for CRU and seed-placed urea. In the second experiment, three N fertilizers (CRU, urea and ammonium nitrate) were broadcast at 30 kg N ha -1 in early spring on plots that had received 0, 30 or 60 kg N ha -1 of CRU at the time of seeding. Inadequate release of spring broadcast CRU was indicated by reduced grain protein concentrations relative to conventional N fertilizers. Under the conditions experienced in our study, CRU substantially increased the maximum safe rate of seed-placed urea, provided minimal benefits to N response relative to side-banded urea, and was less effective than conventional N fertilizers when broadcast in early spring. Key words: N fertilizer use efficiency, slow release, winter survival
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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 | 0.002 | 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".