Cover crop mixtures with multiple plant species are popular, but research shows they don't always outperform single-species cover crops. A review of 27 studies found that in most cases, mixtures and monocultures perform similarly in terms of biomass production, weed suppression, nitrogen scavenging, soil water conservation, soil biology stimulation, crop yield, and production stability. Only in a small percentage of cases did cover crop mixtures perform better than monocultures. Overall, there is limited evidence supporting the idea that diverse cover crop mixtures are consistently superior to single-species cover crops.