Multi-species grass mixes show yield benefits in droughts

Multi-species grassland mixtures increase yield stability, even under drought conditions, a study has shown.

The benefits of multi-species swards were so strong that yields in drought conditions matched or exceeded growth for monocultures grown under normal rainfall.

Results from the two-year trial carried out in Ireland and Switzerland were presented at the British Ecological Society’s annual meeting in Belfast on 11 December.

Researcher John Finn of Teagasc, Ireland said: “Multi-species mixtures can be an effective, farm-scale practical action that could be used to mitigate or even adapt to the effects of severe weather events such as drought.”

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Across Europe, grassland is increasingly being subjected to intense winter rain precipitation and summer droughts.

Protecting yield stability through methods like increasing the species diversity in grassland systems will, therefore, become increasingly important, Dr Finn told ecologists gathered for the conference.

About the trial and the results

The researchers sowed combinations of the four species in different plots to compare monocultures, two-species mixtures and four-species mixtures.

The four species tested on intensively managed grassland were: perennial ryegrass, chicory, red clover and white clover. This revealed that variations in yield decreased as plant diversity increased.

The research was carried out for AnimalChange, an EU project aimed at developing scientific guidance on sustainable development for livestock production under climate change.

During the study the effects of experimental drought conditions on yield stability were substantial.

However, compared to monocultures, higher yields in the four-species mixtures helped to compensate for this reduction.

Over three harvests in Ireland during and just after the drought period, the average monoculture yield of 1.41t/ha dropped to 1.08t/ha. But the multi-species yield was sustained at 1.3t/ha during the drought.

In Agroscope Switzerland’s trials, the average monoculture yield of 1.63t/ha fell to 1.26t/ha under drought.

In stark contrast the multi-species mixture yielded 1.9t/ha in the simulated drought, which was created by growing crops under rain shelters for nine weeks.

The researchers are now looking to extend the length of the study and have expanded the tests from four to six crops, introducing timothy grass and plantain, and looking more closely at levels of nitrogen fertiliser.