Nitrous oxide emissions from variable rate application of nitrogen fertilizer to Panicum virgatum L. in Québec, Canada.
Notice bibliographique
Résumé
Nitrogen (N) fertilizer is essential to maintain agricultural yields but is susceptible to reactions that produce nitrous oxide (N2O), which acts as a greenhouse gas and contributes to stratospheric ozone depletion. It is difficult to predict where these reactions will produce ‘hot spots’ of high N2O fluxes in a field, as well as the ‘hot moments’ when peak N2O fluxes occur. The objective of this study is to relate the N2O fluxes in a Panicum virgatum L. (switchgrass) field to N fertilizer application rates of 0, 50, 100, and 150 kg N ha-1 while considering the spatial-temporal heterogeneity of the field. In summer 2017, soil samples were collected at 128 locations in an 8.87 ha switchgrass field in the Cookshire-Eaton region (45°20'N, 71°46'W) of Québec, Canada. The sandy loam soil was analysed for standard soil test parameters: macro- and micro-nutrient content, pH and texture. In addition, proximal soil sensing was done to characterize the elevation, electrical conductivity and surface spectral reflectance. This data was used to generate a spatial soil map of the field with R 3.4.1 statistical software and ArcGIS, which revealed three distinct management zones in the field. In spring 2018, four N fertilizer rates were applied to blocks (15 m wide x 100 m long), which created four blocks with variable N fertilizer rates in the high-yielding switchgrass zone and four blocks with variable N fertilizer rates in the low-yielding switchgrass zone. Non-flow-through non-steady-state chambers were installed (n=3 per block) for manual gas sampling and N2O fluxes were calculated during a 1 h period every 7-10 d during the growing season. The experiment was repeated in spring 2019 in the same management zones but in newly-selected blocks that had uniform fertilization in the 2018 growing season. Four N fertilizer rates were applied at random to 4 blocks in the high-yielding zone, plus 4 blocks in the low-yielding zone, and gas sampling chambers (n=3) were placed in new locations in each block. The “hot moments” of N2O flux occurred in the first 30 d after N fertilizer application. Although N2O fluxes differed in the management zones in 2018, there were no distinctive “hot spots” in the switchgrass field in the 2019 growing season. However, the cumulative N2O emission in each growing season tended to increase with greater N fertilizer rates, suggesting that applying more N fertilizer increased the risk of gaseous N loss, probably through denitrification. I conclude that precision agriculture techniques based on geospatial characterization of agricultural fields may help to calibrate site-specific N fertilizer inputs and meet agroenvironmental goals by improving crop production while reducing N2O emissions
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
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) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 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 ».