Germinal research offers practical insight into the management of multi-species swards

Germinal Horizon is a research centre belonging to Belfast-headquartered Germinal.

The research results, revealed at the regenerative farming event Down To Earth, held at Grosvenor Farms in Cheshire on Wednesday 3 July, show the effects that establishment timing, grazing regimes and nitrogen application rates have on persistency, quality and yields.

Over the past four years, scientists at Germinal Horizon’s research facility in Melksham, Wiltshire, have been comparing the performance of six mixes: perennial ryegrass (PRG), PRG and clover, and four multi-species mixes containing 8, 9, 14 and 16 components.

The mixes have been trialled using two nitrogen fertiliser application rates of 250kg N/ha and 150kg N/ha.

RESULTS

Yield

Scientists found that perennial ryegrass (PRG) dominates early season yields when herbs are not actively growing, but multi-species come to the fore during the summer (June to September) when perennial ryegrass ‘shuts down’ under drought conditions.

PRG yielded 35.4t of dry matter per hectare over the four years. The addition of clover increased the 4-year yield to 44t of dry matter per hectare, an increase of 8.6t, or an average of 11t per year. Using a multi-species and herb mix produced an extra 11.7t of DM/ha to yield a total of 47t DM/ha over the same period, or an average of 11.78t dry matter/ha per year. This was comparable with the 9-component mix (see summary yield table).

However, as multi-species swards become more complex, yield suffered – the 16-component was the lowest-yielding multi-species mix, growing almost 6t DM/ha less than grass and clover.

Dr Joanna Matthews, Technical Trials Manager at Germinal Horizon Wiltshire, explains: “Multi-species can bolster yields mid-season, even by just adding white clover.

“As the number of components increases, in later years, you are left with fewer primary herbs and the lower content of base grasses in the seed mix at establishment penalises yield.”

Application rates

Higher nitrogen application rates (250kg of N/ha/year) only grew a total 4t more over four years across the six mixtures, on average, compared to those that received 150kg of N/ha/year (mimicking the amount of organic nitrogen applied by grazing animals).

“This extra 100 kg of nitrogen would not be cost-effective when it only returns 1 t/year. Furthermore, nitrogen impacted sward composition; not surprisingly, we saw lower levels of clover when nitrogen was applied at higher rates, but higher levels of grass, chicory and plantain,” explains Dr Matthews.

Establishment timing, persistency and energy density

While later drilling can be effective, Dr Matthews says herbs and clovers are ‘not quick out of the blocks’ and must be established before winter before soil temperatures drop.

She advises: “Multi-species swards need to be established 4-6 weeks before your farm’s usual cut-off date for sowing grass.”

In the first year, herbs were dominant in year one in the 8-and-14-species mixes, but they were largely overtaken by PRG and clover by year two, and by year four, plantain disappeared, and chicory levels fell dramatically.

Clover consistently delivered more energy and protein throughout the season over the four years (11.5 ME MJ/kg and 22.29 per cent crude protein) compared to grass (at 10.7 ME MJ/kg and 20 per cent CP).

Multi-species offered higher protein and energy than grass, but they had more pronounced variations throughout the season and were lowest mid-season, when reproductive growth compromised energy.

Dr Matthews believes the research shows how multi-species can play an important role in helping farmers deal with extreme weather patterns caused by climate change.

“The research shows multi-species swards can make your grazing platform more resilient. By incorporating clover, you will see a yield benefit and can underpin the quality of the sward while fixing nitrogen.”