Abstract
Glyphosate-resistant (GR) crops are produced over large areas in North America. A study was conducted at six western Canada research sites to determine seed date and tillage system effects on weed populations in GR spring wheat and canola cropping systems from 2000 to 2003. Four-year wheat–canola–wheat–pea rotations were devised with varying levels of GR crops in the rotation. Weed populations were determined at pre– and post–in-crop herbicide application intervals in 2000 and 2003. Early seeding led to higher and more variable in-crop wild oat and wild buckwheat populations. High frequencies of in-crop glyphosate wheat in the rotation usually improved weed management and reduced weed density and variability. Canonical discriminant analysis (CDA) across all locations revealed that by 2003, green foxtail, redroot pigweed, sowthistle spp., wild buckwheat, and wild oat, all associated with the rotation lacking in-crop glyphosate. Similar CDA analyses for individual locations indicated specific weeds were associated with 3 yr of in-crop glyphosate (Canada thistle at Brandon, henbit at Lacombe, and volunteer wheat, volunteer canola, and round-leaved mallow at Lethbridge). However, only henbit at Lacombe and volunteer wheat at Lethbridge occurred at significant densities. Although excellent weed control was attained in rotations containing a high frequency of GR crops, the merits of more integrated approaches to weed management and crop production should also be considered. Overall, rotations including GR spring wheat did not significantly increase short-term weed management risks in conventional tillage or low soil-disturbance direct-seeding systems.
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Claims 5
Claim · model-written summary
Early seeding increased and made more variable wild oat and wild buckwheat populations.
- Taxon
- spring wheat
Triticum aestivumt0 - Treatment
- Early seedinge0
- Interactor
- wild oate0weed
- Second interactor
- wild buckwheat
Fallopia convolvuluse0weed - Outcome
- in-crop wild oat and wild buckwheat populationse0
- Direction
- higher and more variablee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Early seeding led to higher and more variable in-crop wild oat and wild buckwheat populations.”
t0“spring wheat”
Claim · model-written summary
Frequent in-crop glyphosate wheat reduced weed density and variability.
- Taxon
- wheatTriticum aestivume0
- Treatment
- High frequencies of in-crop glyphosate wheat in the rotatione0
- Outcome
- weed density and variabilitye0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“High frequencies of in-crop glyphosate wheat in the rotation usually improved weed management and reduced weed density and variability.”
Claim · model-written summary
Several weed species were associated with rotation lacking in-crop glyphosate by 2003.
- Taxon
- spring wheatTriticum aestivumt0
- Treatment
- rotation lacking in-crop glyphosatee0
- Interactor
- green foxtaile0weed
- Second interactor
- redroot pigweede0weed
- Outcome
- green foxtail, redroot pigweed, sowthistle spp., wild buckwheat, and wild oate0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“by 2003, green foxtail, redroot pigweed, sowthistle spp., wild buckwheat, and wild oat, all associated with the rotation lacking in-crop glyphosate.”
t0“spring wheat”
Claim · model-written summary
Henbit at Lacombe and volunteer wheat at Lethbridge occurred at significant densities.
- Taxon
- spring wheatTriticum aestivumt0
- Interactor
- henbit
Lamium amplexicaulee0weed - Second interactor
- volunteer wheate0weed
- Outcome
- henbit at Lacombe and volunteer wheat at Lethbridge occurred at significant densitiese0
- Setting
- Lacombee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“only henbit at Lacombe and volunteer wheat at Lethbridge occurred at significant densities.”
t0“spring wheat”
Claim · model-written summary
Rotations including GR spring wheat did not significantly increase short-term weed management risks.
- Taxon
- spring wheatTriticum aestivume0
- Treatment
- rotations including GR spring wheate0
- Outcome
- short-term weed management riskse0
- Direction
- did not significantly increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rotations including GR spring wheat did not significantly increase short-term weed management risks in conventional tillage or low soil-disturbance direct-seeding systems.”
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