Greenhouse gas emissions from an intensively cropped field under various water and fertilizer management practices
Notice bibliographique
Résumé
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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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».