Quantifying soil water conservation in the semiarid region of Saskatchewan, Canada: Effect of fallow frequency and N fertilizer
Notice bibliographique
Résumé
Soil water is the most limiting factor influencing crop production in the semiarid prairies. The effects of fallow frequency and nitrogen (N) fertilization on soil water conservation were quantified for a 40-yr (1967–2006) field experiment conducted on a medium textured Orthic Brown Chernozem (aridic haploboroll) in semiarid southwestern Saskatchewan, in which soil water contents were measured each year in early spring (generally a week prior to seeding), shortly after harvest, and again just prior to freeze-up in the fall. The three treatments examined were continuous spring wheat (Triticum aestivum L.) (Cont W) and fallow-wheat (F-W), each receiving recommended rates of N and P fertilizer, and Cont W receiving only P. On average, 36% of the precipitation received during the fall and winter months for Cont W (N + P) was conserved in the soil. In the summer fallow system [F-W (N + P)] a greater proportion (42%) of the precipitation was conserved during the first fall and winter. Despite the fact that cumulative precipitation from spring to late fall during the fallow period averaged 243 mm, compared with 152 mm received during the previous fall and winter period, the amount (31 mm) and proportion (13%) of precipitation conserved was considerably less than that during the first overwinter period. These differences were attributed mainly to much higher summer evaporative losses. During the second overwinter period, only 6% of the precipitation received was conserved in the F-W (N + P) system compared with 44% in the first overwinter period. This poor conservation during the second winter was thought to be related to increased snow blowoff due to smaller amounts of standing crop residues, and to the freezing of a wet and bare soil surface, restricting water entry during snowmelt or spring thaw events. Physical based soil-crop models, which must be first improved for overwinter simulations, should be tested on the current data set to further interpret the observations and hypotheses. Compared with the 36% of fall and winter precipitation conserved in Cont W (N + P), inadequate N fertility [Cont W (+ P)] resulted in only 27% of the precipitation being conserved during this period. At harvest, F-W (N + P) and Cont W (N + P) had similar amounts of water in the soil, but Cont W (+ P) had significantly (P < 0.05) more because of reduced water use. However, by the following spring soil water recharge being proportional to crop residues produced resulted in F-W (N + P), Cont W (N + P) and Cont W (+ P) having 252, 209 and 204 mm/1.2 m soil, respectively. Equations were developed that will allow estimation of water conserved as a function of precipitation received between harvest and seeding for F-W (N + P) and Cont W (N + P) (R 2 = 0.52*** in each case). Trends in grain yield were fairly closely correlated with growing season precipitation and potential evapotranspiration [squared semipartial correlation coefficients for Cont W (N + P) 0.32 and 0.17, respectively, and for F-W (N + P) 0.35 and 0.12]; soil water conservation played a minor role in determining final grain yields (squared semipartial correlation coefficient < 0.08). Key words: Soil water, spring wheat, precipitation deficit, yield trends, water conserved trends
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 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 tête enseignante, 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 ».