Cover crops help suppress weeds during transition to annual cropping

Canadian research tested cover crop combinations after terminating a creeping red fescue stand. Hairy vetch produced the most biomass and showed strong weed suppression. However, drought affected canola establishment, so economic results need cautious interpretation.

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The trial compared five cover crop combinations across a three-year rotation, with no fertilizer applied and mowing used to prevent seed set. Hairy vetch alone led biomass production at 7.5 tonnes of dry matter per hectare, while mixtures pairing it with sweet clover or fall rye also formed dense canopies. Field pea lagged behind and allowed greater weed pressure the following season.

Drought conditions in 2025 complicated canola establishment, and an unintended biennial sweet clover variety plus persistent fall rye muddied economic comparisons. Sweet clover with tillage radish yielded the best canola-equivalent return while keeping weeds low. Researchers noted legume residues