Chemical properties of organic amendments influence nitrous oxide emissions from agricultural soils
Notice bibliographique
Résumé
Prediction of organic amendment's (OA) potential to emit soil nitrous oxide (POA-N2O) is difficult because of the variable composition of OAs and of complex interactions with soil properties and environmental conditions. The objectives of this thesis were (1) to conduct a meta-analysis of in-field N2O emissions following OA application to agricultural soils to assess the global emission factor (EF) for all organic sources (EForg) and its modulation by environmental and management-related factors; (2) to determine how experimental conditions affect the POA-N2O and select optimal conditions for laboratory-based assessment; (3) to measure the immediate (P1), short- (P2) and medium-term (P3) POA-N2O with the selected laboratory-based incubation method and then, relate P1, P2, and P3 to the physico-chemical characteristics of more than 131 OAs. The meta-analysis conducted on 256 EFs from 43 sites in 12 countries yielded an EForg equal to 0.57 ± 0.30%, which is lower than the IPCC default EF of 1% for synthetic fertilizer (SF). Three groups of OAs with similar EFs were identified: the high-risk group including animal manures, waste waters and biosolids (1.09 ± 0.17%); the medium-risk group including composts with fertilizers and crop residues with fertilizers (0.46 ± 0.22%); and the low-risk group including composts, crop residues, paper mill sludge and pellets (0.25 ± 0.20%). The EF was modulated by the C/N ratio of the OA, soil properties and precipitation. The EFs were on average 2.8 times greater in fine-textured soils than coarse-textured soils. The comparative incubation study showed that O2-limited conditions in headspace of a sealed-jar system increased the magnitude of N2O fluxes by 1.1 to 2.3-fold compared to open-jar systems. Intermittent aerations of a sealed-jar system relying on repeated measurement periods was then selected to assess P1 (48h), P2 (2nd wk), and P3 (3rd wk). In O2-limited conditions created in a Kamouraska clay soil, maximum P1 was reached for crop residues (CR) with C/N ratio < 15 and liquid manure. Liquid manure (LM) P1 was five-fold greater than solid manure (SM) P1, whereas P2 and P3 were higher in SM- than in LM-amended soils. Physico-chemical properties of OAs explained 23%, 27%, 27%, 56%, and 60% of the variability in P1 response for SM, LM, vegetal compost, poultry manure and CR, respectively. P1 was correlated to the concentrations of water-extractable organic C and volatile fatty acids, NO3-, NH4+, S, equivalent alkalinity and pH of OAs (P < 0.05). In contrast, none of those chemical characteristics were correlated to P2 and P3, suggesting that the increased N2O emissions supported by the OA-C and N substrates occurred within 48 h of adding these OAs to soil. Further investigations are necessary to test the influence of other specific conditions, e.g., soil texture, water content, OA application techniques on POA-N2O and their interactions with OA properties.
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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 | 0,003 | 0,003 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,003 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,001 | 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 ».