Multispecies grasslands produce more yield from lower nitrogen inputs across a climatic gradient

High-yielding forage grasslands frequently comprise low species diversity
and receive high inputs of nitrogen fertilizer. To investigate
multispecies mixtures as an alternative strategy, the 26-site
international ‘LegacyNet’ experiment systematically varied the diversity
of sown grasslands using up to six high-yielding forage species (grasses,
legumes, and herbs), managed under moderate nitrogen inputs. Multispecies
mixtures outyielded two widely used grassland practices: a grass
monoculture with higher nitrogen fertilizer, and a two-species
grass-legume community. High yields in multispecies mixtures were driven
by strong positive grass-legume and legume-herb interactions. In warmer
sites, the yield advantage of legume-containing multispecies mixtures over
monocultures and the high-nitrogen grass increased. Improved design of
grassland mixtures can inform more environmentally sustainable forage
production and may enhance adaptation of productive grasslands to a
warming climate.