Increasing plant diversity in agricultural grasslands boosts yields, reducing reliance on fertiliser

Higher plant diversity in agricultural grasslands increases yields with lower inputs of nitrogen fertiliser. Under warmer temperatures, the yield benefits of more diverse grasslands further increase. There are headline results from a landmark study across 26 international sites as part of LegacyNet, and published in Science. 

Sown productive grasslands (used to supply forage for livestock or as a ley in a crop rotation) typically comprise low species diversity. Two widely used grassland practices comprise 1) a single grass species (monoculture) managed with high inputs of synthetic nitrogen fertiliser, and 2) a two-species grass-legume combination that receives lower inputs of nitrogen fertiliser.

Multi-species swards: more forage with less fertiliser, and more resilient to drought

Based on a Teagasc press release from August 2021

Six-species swards outperformed perennial ryegrass monocultures and were considerably more resistant to drought. New research from Teagasc, Johnstown Castle and Trinity College Dublin shows that multi-species mixtures receiving 150 kg/ha/year of nitrogen fertiliser, out-yielded perennial ryegrass monocultures receiving double that amount of fertiliser (300 kg/ha/year). Increases in plant diversity up to six species in intensively managed grasslands reduced the impact of drought, and produced more yield with less fertiliser.

6-species swards from dairy grazing system at Teagasc, Johnstown Castle. 

Multi-species grassland mixtures: some recent Irish research

Multi-species mixtures are expected to benefit grassland production because of the yield advantage from nitrogen fixed by clover, the variety of rooting structures allows them to access a wider range of soil water and nutrients, and their canopy structure that allows them to intercept more sunlight. In addition, they are associated with lower parasite loads in livestock, reduced greenhouse emissions, and increased carbon sequestration. Here, we give a brief overview of some of our current (2020) research on mixtures at Teagasc, Johnstown Castle.

Plant diversity and yield in agricultural grasslands

There is a lot of discussion about the use of multi-species mixtures within grazed grassland systems. Here, I take a look at *some* of the evidence - but note that this is definitely NOT intended to be a literature review. 

Multi-species mixtures: our publications

I regularly get asked for references to our work on multi-species mixtures. Here’s an overview of the research that we have published over the last 15 years or so.

Experimental drought is underway

At last, the rain shelters are deployed, and our experimental drought is underway.

This just happens to coincide with some of the finest Irish weather in decades, so we may have to irrigate the control plots!

New project: experimental drought on field plots





Knowledge of the effect of severe weather events is a major uncertainty in models that aim to predict the effect of climate change on agricultural systems. As part of the EU-funded AnimalChange experiment, we are testing the effects of severe weather events on grassland production, and the potential role of multi-species mixtures as a mitigation/adaptation measure.