Diverse grasslands deliver higher yields with less fertiliser and greater climate resilience

Can diversity make farming more productive and sustainable? A major new study says yes, and the evidence is compelling. Published in the prestigious journal Science, the research shows that increasing plant diversity in agricultural grasslands can significantly raise yields while reducing reliance on synthetic nitrogen fertiliser. Researchers from Department of Agroecology played a central role in this global effort, which could transform grassland management across Europe and beyond.

The challenge: high yields, low impact

Agricultural grasslands are the backbone of livestock production, providing forage for millions of animals worldwide as well as biomass for energy and green protein production. Traditionally, these systems rely on monocultures of a single grass species, supported by heavy applications of nitrogen fertiliser. While effective for yield, this approach comes at an environmental cost: nitrogen runoff pollutes waterways, contributes to greenhouse gas emissions and undermines soil health.

Farmers face a dilemma: how to maintain productivity while reducing environmental impact and adapting to a warming climate. Could diversity, that is adding more species to the mix, offer a solution.

26 global sites, one question

To find out, researchers from the LegacyNet network coordinated a common experiment across 26 sites in Europe, North America, China and New Zealand, spanning a wide range of climates and soil conditions. Each site compared three grassland systems:

1. Monoculture: a single grass species, managed with high nitrogen inputs.
2. Two-species mix: grass plus legume, with lower nitrogen inputs.
3. Multispecies mixture: six species; two grasses, two legumes and two herbs sown in equal proportions.

The goal: test whether multispecies mixtures could match or outperform conventional systems in yield, while reducing fertiliser use.

The results: more species, more yield

The findings are striking. Across all sites, the six-species mixtures delivered on average 12.3 tonnes of dry matter per hectare per growing season: an 11% increase compared to grass monocultures that received more than twice the nitrogen fertiliser, and an 18% increase compared to the two-species grass-legume combination.

The benefits were consistent across climates and management systems. Even more importantly, the yield advantage of multispecies mixtures grew stronger under warmer conditions, highlighting their potential as a climate adaptation strategy.

Why diversity works

The secret lies in synergy. Grasses provide bulk, legumes fix nitrogen naturally, and herbs contribute resilience and additional nutrients. Together, these species interact in ways that boost overall productivity.

“This research shows conclusively that adding diversity doesn’t reduce yields, it increases them,” says Carsten Malisch, Tenure-track Assistant Professor at Department of Agroecology at Aarhus University and co-founder of LegacyNet. “And these benefits will only become larger with climate change. Beyond the science, this publication marks the culmination of a seven-year journey that began with the founding of LegacyNet during my PostDoc.”

A new model for collaboration

For Diego Abalos, Professor at Department of Agroecology at Aarhus University, the study also signals a shift in how agricultural research is done:
“Such collaborative efforts have been rare in the past, but they should become increasingly common, as they provide essential evidence for supranational organisations like the European Union to identify and promote sustainable agricultural practices across member states.”

Global scale, local impact

The scale of the LegacyNet experiment is unprecedented. Coordinating the same design across 26 sites required years of planning and trust among researchers from multiple disciplines and institutions. This breadth gives the results exceptional robustness and relevance.

“Having a common experiment at many sites enhances our statistical power and greatly improves the generality of our results,” explains Caroline Brophy, Professor of Statistics at Trinity College Dublin and senior author of the study. “The big-picture message is clear: multispecies mixtures can drive more sustainable forage production, improve yields and enhance adaptation to a warming climate. That’s a win-win-win.”

Implications for farmers and policy

For farmers, the message is practical: sowing two grasses, two legumes and two herbs in roughly equal proportions can optimise yield and nitrogen-saving benefits. For policymakers, the findings support strategies that incentivise diversity in agricultural systems aligning productivity goals with environmental targets.

“This research provides farmers with the knowledge to better design grassland leys by sowing approximately equal proportions of grasses, legumes and herbs,” notes John Finn, Senior Researcher at Teagasc and co-author of the study. “Ultimately, we show that multispecies mixtures deliver more yield from less nitrogen fertiliser.”

The story behind LegacyNet

LegacyNet was founded by Brophy, Finn and Malisch with a shared vision: that multispecies mixtures could offer a key solution to improving the performance and sustainability of agricultural grasslands. At the time, no large-scale testing had been done. The first experiment began at Teagasc in Ireland, and from there, the network grew to include researchers from leading institutions across continents. Today, LegacyNet represents a model for collaborative science tackling global challenges.

---

Key facts

• 26 sites across Europe, North America, China and New Zealand.
• Six-species mixtures: two grasses, two legumes, two herbs.
• Yield increase: +11% vs monoculture, +18% vs two-species mix.
• Lower nitrogen inputs, stronger benefits under warmer climates.

---

Read more

The full paper is available in Science: https://www.science.org/doi/10.1126/science.ady0764 
Photos and figures: https://tinyurl.com/2pbu78h6

More information:
Funding: The research was supported by multiple agencies, including Science Foundation Ireland, the Department of Agriculture, Food & the Marine, the European Union’s Horizon 2021 programme under a Marie Skłodowska-Curie grant, and Trinity College Dublin.
Contact: Carsten Malisch, Department of Agroecology, Aarhus University. Tel.: +45 93522566 or email: cmalisch@agro.au.dk

---

---