Data from: The potential of undersown species identity vs. diversity to manage disease in crops

In the absence of chemical control with its negative side effects, fungal
pathogens can cause large yield losses, requiring us to develop
agroecosystems that are inherently disease resistant. Grassland
biodiversity experiments often find plant species diversity to reduce
pathogen pressure, but whether incorporating high biodiversity levels in
agricultural fields have similar effects remains largely unknown. We
tested if undersown plant species diversity could reduce barley disease,
and whether the effect was mediated through above- or belowground
mechanisms, by combining an agricultural field trial with a soil
transplant experiment. As predicted, barley disease decreased in the
presence of undersown plants. Undersown species richness had no effect,
but their abundance led to early season disease reduction. Aboveground
mechanisms underpinned this disease reduction. Barley yield slightly
decreased with increasing undersown species richness, and undersown
species varied in their impact on yield. We identified two undersown
species, Trifolium repens and T. hybridum, that contributed most
to disease reduction and had the potential to increase barley yield.
Furthermore, our results indicate that aboveground mechanisms caused this.
We show that agroecosystem functioning can be improved without trade-offs
on yield by targeted selection of undersown species.