For cover crops, ‘more species’ was not the best predictor of what happened next
WHAT THE EVIDENCE SAYS
A 2019–2022 field experiment compared single-species and functionally assembled cover-crop mixtures across 55 plots, followed by winter wheat. Soil and crop responses depended more on which functional groups were present than on species count alone: an oilseed–legume treatment produced the strongest multifunctionality and subsequent wheat response, while the six-species mixture did not emerge as the best-performing option.
WHY IT MATTERS / OUR READ
For managers, seed-mix richness is a weak stand-in for function. Choose species combinations against the rotation’s actual objectives—nitrogen, rooting, residue, weed suppression, soil biology and cash-crop performance—and monitor the following crop instead of assuming a more diverse mix is automatically more beneficial.
CAVEATS / UNCERTAINTY
The diversity gradient was unbalanced, with only one high-diversity mixture and one fallow control, so richness effects cannot be cleanly separated from composition. An exceptional 2021 drought caused cover-crop failure, the experiment was short, and results are specific to a dryland Palouse rotation rather than a universal cover-crop prescription.
SOURCE
Journal of Applied Ecology
View original evidence ↗
In a four-year Pullman experiment, functional composition—not mix richness—best explained soil and winter-wheat responses; one oilseed–legume combination outperformed the six-species mix.
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