A research trial into yields as a result of sowing multi-species swards has revealed that using an additional 100kg of nitrogen N/ha only yielded an extra 1t of DM/ha/year and may not be cost effective.
The research carried out by Germinal Horizon has offered practical insights into how farmers can build resilience into their grazing systems by using multi-species mixes to maintain growth throughout the season.
The results are being revealed at the regenerative farming event Down To Earth, held at Grosvenor Farms in Cheshire today (Wednesday, July 3), show the effects that establishment timing, grazing regimes and nitrogen application rates have on persistency, quality and yields.
Research trial
Over the past four years, scientists at Germinal Horizon’s research facility at 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.
Yield
Scientists found that PRG dominates early season yields when herbs are not actively growing, but multi-species come to the fore during the summer (June-September) when perennial ryegrass ‘shuts down’ under drought conditions.
PRG yielded 35.4t of DM/ha over the four years. The addition of clover increased the four-year yield to 44t of DM/ha, 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 DM/ha per year. This was comparable with the nine-component mix.
However, as multi-species swards become more complex, the research results show that yield suffered – the 16-component was the lowest-yielding multi-species mix, growing almost 6t DM/ha less than grass and clover.
Technical trials manager at Germinal Horizon Wiltshire, Dr. Joanna Matthews said: “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 N 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 100kg 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,” Dr. Matthews added.
Establishment timing, persistency and energy density
While later drilling can be effective, Dr. Matthews said herbs and clovers are ‘not quick out of the blocks’ and must be established before winter before soil temperatures drop.
She advised: “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% crude protein) compared to grass (at 10.7 ME MJ/kg and 20% 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.”
Choosing multi-species swards
- Know your soils when choosing suitable species: Germinal’s Multi-Species Grazing mixes are suitable to nearly all soil types, but more diverse swards will only be suitable to certain soils;
- Consider what you want to achieve before choosing components in a mix: Clover is a great source of energy for finishing animals and perennial ryegrass will provide early-season growth, but herb species can provide other benefits such as bolstering first-year production;
- Establishment: Sow herbs into warm, moist conditions so they establish well before winter;
- Use nitrogen efficiently to feed PRG in the spring and then allow clover to do its job.
