Soil tests for predicting the N requirement of corn
Bibliographic record
Abstract
Several soil N tests were compared with the one currently used for predicting the N requirement for corn in Ontario. The current test involves a measurement of nitrate (NO3−, 0–30 cm) before N fertilizer sidedressing. The study was done to determine the efficacy of other tests for N fertilizer prediction. The tests chosen varied in the quantity of N “extracted” and included hot KCl-extractable NH4+, anaerobically released NH4+, extractable NH4+ following autoclaving in CaCl2 solution and total N of soil sampled to a depth of 30 cm. The 3-yr study was conducted on a sloped (simple) field site, which provided a wide range in soil organic matter (SOM) contents. A corn crop was grown each year following a barley crop with or without red clover cover crop residues incorporated in the spring and with or without N fertilization. Corn grain yields were obtained at the end of the growing season. Grain yields were lowest at the shoulder and backslope locations and highest at the footslope and toeslope locations. Corn plant shoot biomass and N content and soil mineral (NH4+and NO3−) N (0–30 cm) were measured biweekly to provide an estimate or index of available N. Plant and soil samples were taken at the summit, shoulder, backslope, footslope and toeslope locations providing a wide range of SOM levels, which, in turn, provided a range in available N for comparing the various soil N tests. The increase in estimated available N during the growing season was most rapid in the 120–180 day of year (DOY) period and substantially slower in the 230–260 DOY period. An available N index (AVN) was obtained by averaging the N measured with three plant and soil samples taken in the late August to early September period. Thus, the AVN was determined during a period when the increase in available N was relatively slow. Regressions of corn grain yield (not fertilized with N) on AVN produced R2 values ranging from 0.61 to 0.93. Values of R2 for AVN vs. the soil tests ranged from 0.34 to 0.88 where red clover crop residues were not involved. The AVN values were less correlated with the soil N test values where red clover cover crop residues were incorporated with R2 values ranging from 0.11 to 0.92. It was concluded that the hot KCl test would be a suitable alternative to the currently used soil NO3− test because of relatively simple soil sample preparations and storage, and analytical procedures. Key words: Soil N tests, corn, available N index, soil organic matter, landscape location
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 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".