Greenhouse gas emissions from an intensively cropped field under various water and fertilizer management practices
Bibliographic record
Abstract
Water table management has not only proven to have positive effects on crop yields but can also improve water quality by reducing nitrate concentrations in the drainage water, and by regulating drain outflow volumes. However, a higher water table level may also lead to soil conditions favorable to denitrification and organic matter decomposition, resulting in increased soil emissions of greenhouse gases (GHG). The main objective of this study was to investigate the influence of two water management systems on greenhouse gas fluxes: conventional tile drainage (FD) and controlled tile drainage with sub-irrigation (CDSI). The second objective was to investigate the effects of five different doses of N-fertilizer application: 70 kg N/ha, 170 kg N/ha, 200 kg N/ha, 230 kg N/ha in one application and 230 kg N/ha in two applications with a one-week interval. This study particularly focused on the combined effects of water table management and the fertilizer amounts. The study was conducted on a 4.2-ha sandy loam field located in South-western Quebec, Canada. Within the four years of this study, the crop rotation was yellow beans followed by three years of grain-corn. GHG fluxes (carbon dioxide, nitrous oxide and methane) were obtained using a vented non-steady state closed chamber method, with measurements taken at 15-minute intervals over a one-hour period, for 9 days throughout the growing season in 2012, for 14 days in 2013, for 21 days in 2014 and for 24 days in 2015. In addition, the following parameters were measured: daily rainfall amounts, daily air temperature, and both soil volumetric water content and soil temperature at the time of sampling. Agronomic management practices were recorded. Increasing N-fertilizer amounts accelerated soil respiration, methane oxidation and the production of nitrous oxide. For fertilizer amounts of 200 kg N/ha and more, large punctual bursts of nitrous oxide production (≥ 0.5 mg N-N2O.m-2.hr-1) were measured approximately 15-20 days following fertilizer application. Sub-dividing total N-fertilizer into two applications spaced one-week apart reduced the bursts of nitrous oxide production. In 2013, nitrous oxide production was present prior to harvest, which was attributed to microbial consumption of fixed nitrogen from the green manure and yellow bean residues of the previous year. The corn canopy created a microclimate within the field and regulated both soil temperatures and soil volumetric water contents in this study. Soil temperature was a stronger regulator of GHG fluxes compared to soil water content. Neither FD nor CDSI were found to have significant effects on any of the GHG fluxes.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 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".