Abstract
Ecological concepts derived from perennial grasslands suggest multi‐species cover crop mixtures maximize ecosystem function. However, legacy effects of diverse cover crops on agricultural soil properties, microorganisms and crop yields remain unclear. To address this knowledge gap, we planted six species of cover crops individually, in functional group combinations (representing oilseeds, grasses or legumes), or with all species combined (high diversity treatment). We then investigated how cover crop treatment affected winter wheat yield, soil biogeochemical properties, microbial community composition and ecosystem multifunctionality. Contrary to our expectations, the high diversity treatment reduced wheat yield and minimally affected soil properties relative to the fallow control. We observed the greatest positive impact on agroecosystem multifunctionality and wheat yield in the oilseed + legume treatment. Soil pH was mediated by cover crop treatment and identified as the key factor influencing bacterial diversity and composition, while active microbial biomass during the preceding cover crop was the best predictor of subsequent winter wheat yield. Synthesis and applications . Cover crop composition, not diversity, was the strongest driver of changes to, and legacy effects on, soil microbial communities, agroecosystem multifunctionality and wheat yield. Our results highlight the importance of selecting cover crops that promote positive plant–microbe–soil feedbacks and maintain agroecosystem sustainability.