Abstract
In addition to soil health and conservation benefits, cover crops (CCs) may offer weed control in the midwestern United States, but individual studies report vary- ing effects. We conducted a meta-analysis of studies measuring weed biomass (WBIO) or density (WDEN) in paired CC and no-cover treatments in corn (Zea mays L.)–soybean [Glycine max (L.) Merr] rotations in the U.S. Midwest. Fifteen studies provided 123 paired comparisons of WBIO and 119 of WDEN. Only grass CCs significantly reduced WBIO, while no CC reduced WDEN. We found no evidence CC management factors (e.g., termination method) directly affected out- comes. Our dataset showed that a 75% reduction in WBIO requires at least 5 Mg ha−1 of CC. Simulations from a process-based model (SALUS) indicated achieving 5 Mg ha−1 requires substantially earlier fall planting and later spring termination in most years, conflicting with typical cash-crop planting and harvesting. We conclude CCs significantly reduce WBIO, but current CC management constraints render these reductions variable and uncertain.
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Claims 6
Claim · model-written summary
Grass cover crops reduced weed biomass.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Only grass CCs significantly reduced WBIO, while no CC reduced WDEN.”
e1“weed biomass (WBIO) or density (WDEN) in paired CC and no-cover treatments in corn (Zea mays L.)–soybean [Glycine max (L.) Merr] rotations in the U.S. Midwest.”
Claim · model-written summary
No cover crop reduced weed density.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Only grass CCs significantly reduced WBIO, while no CC reduced WDEN.”
e1“weed biomass (WBIO) or density (WDEN) in paired CC and no-cover treatments in corn (Zea mays L.)–soybean [Glycine max (L.) Merr] rotations in the U.S. Midwest.”
Claim · model-written summary
Cover crop management factors had no detected direct effect on weed outcomes.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We found no evidence CC management factors (e.g., termination method) directly affected out- comes.”
e1“weed biomass (WBIO) or density (WDEN) in paired CC and no-cover treatments in corn (Zea mays L.)–soybean [Glycine max (L.) Merr] rotations in the U.S. Midwest.”
Claim · model-written summary
A 75% weed biomass reduction required at least 5 Mg ha−1 cover crop biomass.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Our dataset showed that a 75% reduction in WBIO requires at least 5 Mg ha−1 of CC.”
e1“weed biomass (WBIO) or density (WDEN) in paired CC and no-cover treatments in corn (Zea mays L.)–soybean [Glycine max (L.) Merr] rotations in the U.S. Midwest.”
Claim · model-written summary
Model simulations indicated cover crop biomass of 5 Mg ha−1 required earlier fall planting and later spring termination in most years.
- Treatment
- earlier fall planting and later spring terminatione0
- Outcome
- achieving 5 Mg ha−1e0
- Value
- 5 Mg ha−1e0
- Qualifier
- in most yearse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Simulations from a process-based model (SALUS) indicated achieving 5 Mg ha−1 requires substantially earlier fall planting and later spring termination in most years, conflicting with typical cash-crop planting and harvesting.”
e1“weed biomass (WBIO) or density (WDEN) in paired CC and no-cover treatments in corn (Zea mays L.)–soybean [Glycine max (L.) Merr] rotations in the U.S. Midwest.”
Claim · model-written summary
Current management constraints make cover crop weed biomass reductions variable and uncertain.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We conclude CCs significantly reduce WBIO, but current CC management constraints render these reductions variable and uncertain.”
e1“weed biomass (WBIO) or density (WDEN) in paired CC and no-cover treatments in corn (Zea mays L.)–soybean [Glycine max (L.) Merr] rotations in the U.S. Midwest.”
The same questions in other papers
cover crop · weed · Zea mays (maize)Results differ
35 papers in the same direction as this paper · 10 in the opposite direction · 2 reporting no difference from an alternative
- positive
- positive
- no effect
44 papers more in this group
See all 48 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.