Do diverse cover crop mixtures perform better than monocultures? A systematic review

Multi-species cover crop mixtures have been increasing in popularity. It has been hypothesized these mixtures produce more biomass, suppress more weeds, scavenge more N, conserve more soil water, stimulate more soil biology, promote higher yields of subsequent crops, and have higher production stability than the best of their monoculture counterparts. This systematic review synthesizes a growing body of cover crop mixture research to assess, for these metrics, whether cover crop mixtures can perform better than their constituent species when planted alone. Searching three databases, we identified 27 studies which compared cover crop mixtures (containing at least three species) to all their constituent species. The studies contained 119 sampled cover crop plantings that met our eligibility criteria. From these, we extracted 243 full comparisons of the best-performing mixture and best-performing monoculture for the selected metrics. In 88% of these comparisons, the monoculture and mixture performed comparably. In 10% of the comparisons, the monoculture did better, and in 2% of comparisons the mixture performed better. Overall, there are few published studies documenting the superiority of cover crop mixtures over monocultures for our selected metrics.