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 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.

Four-species mixtures increased weed suppression in intensively managed grasslands

Diversity robustly suppresses weeds in intensive grassland systems

How can we get more from less use of natural resources in agricultural systems? The use of multi-species mixtures (plant diversity) in intensively managed systems has been proposed as one strategy to improve agricultural sustainability. We show that four-species forage mixtures greatly increased weed suppression in intensively managed grasslands.

Uncontrolled weed growth can represent a major source of inefficiency, diverting nutrients, water, light and labour to an undesirable form of biomass, while herbicides incur significant environmental and economic costs. In pastures, weeds can impair forage quantity and quality resulting in reduced animal production, and increase the need for reseeding with its consequent costs. If diversity helps in maintaining a low level of weeds in pastures (and increases yield) it can increase the sustainable production of higher quality forage compared to systems relying on monocultures.  

 

Benefits of legume-based livestock systems (Conference presentation)

Following my recent post on the EGF 2013 (European Grassland Federation) Symposium in Iceland, presentations are now available at the EGF 2013 homepage
Update: Proceedings now available at: http://www.egf2013.is/

Our research at European Grassland Federation 2013

The Role of Grasslands in a Green Future

Proceedings of the 17th Symposium of the European Grassland Federation (Eds. Áslaug Helgadóttir, Alan Hopkins)

Akureyri, Iceland, 23-26 June 2013

This was another excellent EGF conference at a wonderful location in Akureyri, Iceland. The scientific programme was as impressive as the social programme, which featured waterfalls, geysers, choirs, horse exhibitions, and 'cured shark'. Cured shark is certainly an acquired taste, and was considered by one participant as tasting like 'a baby's nappy' (or what they imagined a baby's nappy would taste like...).

Here, I provide the titles, abstracts and contact details of the four contributions that we made to EGF2013. Of particular interest was the growing frequency of research into multi-species mixutres of grasses and legumes. The opening talk by my good friend and long-time collaborator Andi Lüscher was a tour de force of this theme, and his paper will be published in Grass and Forage Science in due course. I also provide the abstract of his talk.  

Public dissemination of our research on grassland production

Science for Environment Policy is a free news and information service published by Directorate-General Environment, European Commission. It provides quality environmental research for evidence-based policy.

The June 2013 issue featured our recently published research:

"Multi-species mixtures for greater productivity and environmental resilience

A recent study has revealed that grassland plots planted with a mixture of several agricultural plant species produced a greater yield than plots planted with a single species. The findings provide valuable evidence for scientists, farmers and policymakers who strive to increase the productivity of grassland, while reducing input of nitrogen fertilisers."

This publication was based on our recent journal article:

Finn, J. A., Kirwan, L., Connolly, J., et al. (2013) Ecosystem function enhanced by combining four functional types of plant species in intensively managed grassland mixtures: a 3-year continental-scale field experiment. Journal of Applied Ecology. 50: 365-375.

Doi: 10.1111/1365-2664.12041

UPDATE: Open Access version at: http://hdl.handle.net/11019/438

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.