New research from Teagasc, Johnstown Castle and Trinity College Dublin has shown that multispecies mixes receiving 150kg/ha/year of nitrogen outperformed perennial ryegrass receiving double the amount of fertiliser.
It was also found that in intensively managed grasslands, increases in plant diversity up to six species reduced the impact of drought as well as producing more yield with less fertiliser.
Over the two years of trials, mixtures with all six species produced the highest yields on average and beat the best of the six monocultures in terms of yields.
Under rainfed conditions, the mixture with equal proportions of all six species at sowing performed better than the best-performing monoculture.
The six-species mix produced 11.8t/ha/year in comparison to the best-performing monoculture, which yielded 10.5t/ha/year.
Total annual yields were reduced under experimental drought conditions.
Nevertheless, higher-diversity lower-input mixes under unfavourable drought conditions achieved similar yields to those from the low-diversity, high-input comparison under rainfed conditions.
This shows clearly the potential for multispecies mixtures to mitigate the effect of more variable weather conditions on grassland yields throughout the whole year, Teagasc said.
What grass/legume/herb mixes should you choose?
Studies have shown the most productive swards were a combination of species from the three functional groups of grasses, legumes and herbs. Mixes with legume proportions ranging from 30% to 70% produced yields greater than those of the best monoculture.
Guylain Grange, Teagasc Walsh Scholar who conducted the experiment, said: “Multispecies mixtures can be a practical, farm-scale solution for intensive grassland production with nitrogen fertiliser input, and can mitigate the risk associated with summer droughts due to climate change.
“Further research at Teagasc is investigating the use of multispecies mixtures under grazed conditions.”