Cover crops and weed suppression in the U.S. Midwest: A meta-analysis and modeling study

Authors

Virginia Nicholas, Iowa State UniversityFollow
Rafael Martinez-Feria, Iowa State UniversityFollow
David Weisberger, University of Georgia
Sarah Carlson, Practical Farmers of Iowa
B. Basso, Michigan State UniversityFollow
Andrea Basche, University of Nebraska - LincolnFollow

ORCID IDs

https://orcid.org/0000-0003-1850-8243

https://orcid.org/0000-0002-4230-5684

https://orcid.org/0000-0003-2090-4616

https://orcid.org/0000-0001-6805-8522

Date of this Version

2020

Citation

Agric Environ Lett. 2020;5:e20022.

https://doi.org/10.1002/ael2.20022

Comments

2020 The Authors.

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.