Crop cover is more important than rotational diversity for soil multifunctionality and cereal yields in European cropping systems

In natural ecosystems, positive effects of plant diversity on ecosystem functioning have been widely observed, yet whether this is true in cropping systems remains unclear. Here we assessed the impact of crop diversification on soil microbial diversity, soil multifunctionality (SMF) and crop yields in 155 cereal fields across a 3,000 km north–south European gradient. Overall, crop diversity showed a relatively minor effect on soil microbial diversity, SMF and yields. In contrast, the proportion of time with crop cover (including cash crops, cover crops or forage leys) during the past ten-year crop rotation had a much stronger impact. This suggests that increasing crop cover can enhance both yields and soil functioning, while also providing habitat for soil microorganisms. We found that SMF did not positively contribute to crop yields, highlighting that care must be taken to balance the provision of food with environmentally beneficial functions and services, since they do not always go hand in hand. The Digging Deeper project was funded through the 2015–2016 BiodivERsA COg call for research proposals, with the national funders Swiss National Science Foundation (grant 31BD30-172466), Deutsche Forschungsgemeinschaft (317895346), Swedish Research Council Formas contract 2016-0194), Ministerio de Economía y Competitividad (Digging_Deeper, reference PCIN-2016-028) and Agence Nationale de la Recherche (ANR, France, grant ANR-16-EBI3-0004-01).