Recent biodiversity experiments using sown plant communities suggest a positive effect of plant species diversity on ecosystem functioning and resource use. However, are these experimental results applicable to agriculturally managed grassland? In a new study published in AoB PLANTS, Petersen and Isselstein analysed vegetation structure and light interception in managed grassland in which species composition had been manipulated by herbicides. They expected the functionally more diverse plots (grasses and forbs in equal amounts) to better intercept the light than plots containing more than 90% grasses due to an optimal arrangement of leaves in space. However, management (fertilization and mowing regime) had a much stronger influence on structure and light interception than plant species composition.