The influence of ecological cropping practices on aggregate stability: results from two long-term studies
Notice bibliographique
Résumé
Agricultural cropping practices, including crop rotations with annual grains and perennial forages, cover crops, and no-till and organic management influence soil processes. Aggregate stability is a soil property that relates to many different physical and biological functions of the soil, and as such is an important indicator of soil health. It was hypothesized that aggregate stability would be improved through the following cropping system interventions: 1) including two years of alfalfa (Medicago sativa L.) in an organic annual grain rotation; 2) adding composted manure to long-term organic systems; 3) including four years of perennial forages in rotation with annual grains as a one-time intervention for system rehabilitation; and 4) including cover crops in a no-till crop rotation. Furthermore, the first two cropping system interventions were compared to conventional rotations and long-term grasslands. This research took place at two long term studies, a rotation study in southern Manitoba and a cover crop study in south eastern Saskatchewan. The rotation study included an annual grain rotation, consisting of wheat (Triticum aestivum L.) - flax (Linum usitatissimum L.) - oat (Avena sativa L.) - hairy vetch (Vicia villosa Roth) / barley (Hordeum vulgare L.) green manure, and a perennial forage and grain rotation (wheat-flax-two years of alfalfa). Composted manure was added to the organic forage grain rotation every four years. The cover crop study used black medic (Medicago lupulina L.) as a self-regenerating cover crop. Black medic produces large amounts of seed and regrows each spring, to grow under the crop and continues to grow in the fall after harvest. It was grown in a no-till wheat-flax-canaryseed (Phalaris canariensis L.) rotation at two nitrogen fertilizer levels. Aggregate stability samples were taken in both wheat and flax phases of the rotations at both sites in the spring of 2017 and 2018. A wet sieving procedure using stacked sieves with five mesh sizes was used to determine mean weight diameter (MWD) of stable aggregates. At both study sites grassland areas had higher MWD and generally more 1-6.3mm aggregates and fewer 0.25-1mm aggregates than the arable treatments. In a few cases the rotations with a perennial forage component had similar AS to the grasslands. The perennial forage increased MWD under organic management at 10-20cm depth. Manure additions did not affect AS, and in most cases neither did the perennial forage in rotation. The presence of alfalfa in the alfalfa intervention increased AS but the number of years in alfalfa did not. The black medic cover crop increased MWD with low nitrogen fertilizer in the wheat phase but not the flax phase of rotation. It was concluded that long term grasslands and cover crops were the most effective ways to improve AS at these sites.
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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) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,001 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,000 | 0,001 |
| Intégrité de la recherche | 0,001 | 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 ».