The negative impact on the environment caused by the excessive use of synthetic plant protection products is the reason for the search for more environmentally friendly methods of controlling harmful species, including weeds. Cover crops are increasingly used in agricultural practice, because in addition to weed control, they provide many other ecosystem services (preventing the leaching of nutrients, preventing erosion, increasing organic matter in the soil and consequently improving soil fertility, increasing biodiversity, supporting pollinators, etc.). More diverse mixtures of cover crops are becoming popular. These mixtures are expected to be better and more stable across different growing seasons compared to individual species sown as monocultures. The purpose of our experiment was to determine whether it is possible to achieve sufficient weed control with species-rich mixtures while also ensuring the adequate development of most species in the mixture up to the flowering stage. We also aimed to compare the mixtures to the pure cultivars in terms of important agronomic properties (soil cover and biomass production) to see if the mixtures outperform the dominant species that make up the mixture. We found that four of the eight mixtures provided better weed control than all of their dominant species sown as pure species. Our data suggest that mixtures can be more successful in controlling weeds than single cultivars if highly competitive cultivars are selected and appropriate seeding rates are used. In our experiment, all the mixtures flowered for as long as or longer than the pure cultivars. When evaluating several ecosystem services of cover crops simultaneously (weed suppression, biomass accumulation, pollinator support, nitrogen fixation), most mixtures were more successful than pure cultivars.
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