Could two be better than many when it comes to sward species?

Research is also needed to improve establishment and persistency of MSS, and to evaluate suitable grazing strategies and the role of MSS in drought conditions, according to an external review of Teagasc pasture research.

Multispecies swards typically include PRG, cocksfoot, Timothy, red and white clover, chicory and plantain herbs. MSS were found to perform similarly to PRG/white clover swards in herbage production and animal performance. 

But the more recent studies showed lack of persistency is a major MSS issue, with chicory, red clover and plantain largely disappearing within two to three years of establishment.

The recently completed review of Teagasc pasture research highlighted perennial ryegrass (PRG) and white clover swards, when managed appropriately, can maintain pasture dry matter production, increase animal performance, reduce greenhouse gas emissions, and increase farm profitability. 

This sward (with 20 to 25% white clover over the grazing season on average), while getting 100kg/ha less chemical nitrogen, produced similar pasture production to a perennial ryegrass only sward. 

The biggest challenge identified on farms was in the establishment and maintenance of the white clover content.

Reducing fertiliser nitrogen is one of the ways to reach the Government’s Climate Action Plan target to reduce greenhouse gas emissions from agriculture by 25% by 2030. 

And where biologically fixed nitrogen from legumes replaces chemical nitrogen, there is potential to improve farm profitability, with trials showing the fertiliser replacement effect, in addition to higher milk production or live weight gain.

There was also evidence PRG/white clover swards emitted less nitrous oxide emissions.

Teagasc research also indicated a relatively low risk of bloat at 20-25% white clover, but vigilance is required. With clover content over 30%, and low herbage dry matter content, the risk of bloat is much greater, and careful monitoring of livestock plus use of preventative measures are required.

But wide variation in performance of PRG/white clover swards emerged as a major concern in the review, pointing to a need for more detailed research on biological nitrogen fixation by white clover in a range of sward conditions and soil types.

Further research was also called for to develop fertiliser nitrogen recommendations for PRG/white clover swards, with consideration of variables such as clover content, soil temperature, soil type, geographic location, legacy nitrogen from the previous autumn, manure nitrogen (from slurry and grazing animals), herbage yield, and soil nitrogen mineralisation.

Teagasc is developing a Clover Profit Index. There has been evidence of differences between clover varieties in nitrogen-fixing ability and tolerance to compete in mixed swards.

The external review pointed to other research needs, such as investigating strategic over-sowing to maintain a high proportion of white clover in the sward, and the role of PRG/white clover with non-rotational grazing on beef and sheep farms (including the potential of zero fertiliser nitrogen systems). 

Teagasc said there had been limited adoption of PRG/white clover on dairy farms, but uptake on beef and sheep farms has been much slower, despite their much lower fertiliser nitrogen use.

Meanwhile, Teagasc research has shown PRG/red clover silage systems can produce high dry matter yields with low chemical nitrogen and little impact on animal performance. 

The external review recommended further research on PRG/RC for silage should focus on opportunities to maximise the use of manure nitrogen as the primary source of N and varietal differences in yield and persistency.