Over two years into a four-year project to incorporate clover into all dairy, beef and sheep grazing swards at CAFRE Greenmount, it is clear that transitioning away from ryegrass-only swards comes with a number of practical challenges.
At a clover open day held last Thursday at the beef and sheep centre at Greenmount, CAFRE advisers acknowledged that a four-year timeframe is “ambitious” and for most commercial farms, it would probably take 10 years to fully switch to grass-clover swards.
The key issue is the lost production in the first year, irrespective of reseeding method. Ultimately, even if clover establishes successfully, it will be the following year before the clover starts to actively fix nitrogen (N) from the atmosphere.
“Four years is ambitious – we wouldn’t recommend that to any farmers,” confirmed CAFRE technologist, Robert Patterson.
The pressure is most acute at the 180-cow Greenmount dairy unit. The herd is autumn calving, so there is a high demand for grass in spring and early summer. However, taking paddocks out to establish clover has meant cows have had to walk further to access grass originally earmarked as second- or third-cut. That has literally eaten into silage reserves. In 2023, there was a reserve of 600t, which dropped to 400t last year and currently stands at around 100t.
Despite that cost, there is a big win to be had – if the main dairy unit is able to grow similar amounts of forage having spread 150kg N/ha rather than 250kg N, it will result in significant long-term financial savings. There is also lots of research to show there is improved animal performance on grass clover swards.
“I am fairly hopeful when we get to year four or five we will be over the worst bit – we are in a transition phase at present,” said Patterson.
A relatively small crowd attended the clover open day at Greenmount. \ Peter Houston
Overseeding versus traditional cultivation
The preferred method used at Greenmount to establish clover is to overseed/stitch into a young and weed-free perennial ryegrass sward.
One of the main benefits is that the sward is back into the normal grazing rotation after 18 days. But to ensure new clover plants are not shaded out by grass, the swards need to be grazed every 12 to 14 days in their first year.
On the beef and sheep farm, no chemical nitrogen (N) fertiliser is used, but on the dairy unit, a half rate of around 12kg N is applied at sowing. No N is put on after the first grazing, but after that, the half rate of N is spread.
“The reduced N means there is 2 to 3t less yield in that year,” said Robert Patterson.
However, the alternative is spraying off the sward, followed by various cultivations and sowing out. In most cases that paddock is out of action for 12 to 14 weeks, so it has a major impact, especially if done in the spring.
Going forward, Patterson said if any full reseeds are required on the dairy platform, they will be done in the autumn to minimise the loss in production.
While best practice advice is for clover to be sown in spring and early summer months, a reseed at the Greenmount dairy unit last September did include clover.
A good autumn followed by a relatively mild winter allowed the clover to get established and it has been grazed three times with cows so far in 2025.
Established
Once a new clover sward is established, Patterson said it was important to get it grazed out using sheep by mid-November each year.
From spring onwards, he emphasised the need to avoid grass out-competing clover, so cows should go into swards with a cover of 2,700 to 2,800 kg dry matter per hectare (DM/ha) rather than the normal 3,000kg opening cover. “It is an 18-day rotation rather than 21 days,” he said.
Before sowing, two passes are done with a grass tine harrow to create some tilth.
Varying levels of success oversowing clover
Whether overseeding is successful in establishing clover is dependent on a number of factors, especially the weather post sowing.
At Greenmount, the aim is to overseed paddocks in the spring, however, in 2025, dry weather put a stop to that for most of May. Some moisture is necessary if clover is to get established.
Given the unpredictability of spring weather in NI, it has resulted in variable results when oversowing clover.
Adding to that are differences dependent on level of cultivation done and the machine being used.
Greenmount has utilised both an Erth and an Aitcheson drill to stitch in clover, but neither was effective in some instances.
Instead, the preferred technique is now to scarify the surface of the field with grass tines in two directions before sowing using an Einbock grass seeder, followed by rolling.
Clover is sown at a rate of 2.5kg per acre, split equally across two varieties (Buddy and AberHerald). Ideally, the sward has been cut for bales or as a minimum, it is grazed very tightly before sowing.
Weeds
While there is now a new clover-safe spray on the market in the form of ProClova, ideally any weeds should be dealt with in the previous year, suggested CAFRE adviser Trevor Alcorn.
He said soil pH should be around 6.5, with phosphorus and potassium applied based on soil analysis.
The overall aim at Greenmount is to achieve 30% white clover content in each sward, which is generally seen as the amount necessary to fix sufficient N to drive growth.
In practice, a lot of paddocks at Greenmount have had 10% clover in the first year post sowing, so the process has had to be done a second time.
“It is very difficult to go from 0 to 30% in one year with overseeding,” confirmed Robert Patterson.
The Einbock drill is used to overseed clover into existing swards at Greenmount.
A good year for red clover
In 2023, a total of 1.6ha was sown out in a red clover sward at Greenmount.
When establishing red clover, it is necessary to burn off the old sward and do a full reseed, said Robert Patterson from CAFRE.
One cut of bales was taken off during the wet autumn of 2023 and “everywhere the baler went, the clover died,” he said.
However, 2024 was different, with good-quality red clover silage made and that has carried through into the first-cut taken in 2025.
The crop is grown with no N and just slurry. The 2024 silage was offered to 12 dairy cross bullocks, with a separate pen of 12 offered grass silage. The cattle on the red clover gained an extra 0.4kg/day.
“It is not a research trial, but in our experience, the cattle hoovered it up – they loved it,” said Patterson.
Clover will help to lower GHG emissions on farms
The 124ha beef and sheep farm at Greenmount is stocked with around 100 suckler cows to beef and 210 ewes.
Total greenhouse gas (GHG) emissions on the farm are currently estimated at 1,250t carbon dioxide equivalent. However, around 15km of hedges and 5ha of woodland on the farm sequester around 308t annually, leaving net emissions at 941t.
The aim is for the farm to be 50% carbon neutral by 2050 against a 2019 baseline. Achieving that will require the adoption of new technologies as well as widespread incorporation of the likes of clover to replace chemical fertiliser use.
“Hedges and woodland are not going to make our farms carbon neutral. That is why we need to look at clovers etc. There is no easy fix to lower emissions,” suggested Dr Elizabeth Earle from CAFRE.
NUE-Leg demo at Greenmount
As part of a UK project looking at Nitrogen Use Efficiency in Legumes (NUE-Leg), a demonstration area is to be sown at Greenmount this year, forage consultant Dr Trevor Gilliland told last Thursday’s event.
NUE-Leg is a £4.7m project announced in 2024 which brings together plant breeders, research organisations and commercial companies to look at novel legume varieties. That includes the likes of improved white clover varieties resistant to drought and cold as well as red clover that would be tolerant to livestock grazing.
“You will be able to come here next summer to see the progress made,” he said.
“At the start of this project, our ambition is to take the 150kg N that can potentially be fixed by clover and double that, if not more,” added Gilliland.
Over two years into a four-year project to incorporate clover into all dairy, beef and sheep grazing swards at CAFRE Greenmount, it is clear that transitioning away from ryegrass-only swards comes with a number of practical challenges.
At a clover open day held last Thursday at the beef and sheep centre at Greenmount, CAFRE advisers acknowledged that a four-year timeframe is “ambitious” and for most commercial farms, it would probably take 10 years to fully switch to grass-clover swards.
The key issue is the lost production in the first year, irrespective of reseeding method. Ultimately, even if clover establishes successfully, it will be the following year before the clover starts to actively fix nitrogen (N) from the atmosphere.
“Four years is ambitious – we wouldn’t recommend that to any farmers,” confirmed CAFRE technologist, Robert Patterson.
The pressure is most acute at the 180-cow Greenmount dairy unit. The herd is autumn calving, so there is a high demand for grass in spring and early summer. However, taking paddocks out to establish clover has meant cows have had to walk further to access grass originally earmarked as second- or third-cut. That has literally eaten into silage reserves. In 2023, there was a reserve of 600t, which dropped to 400t last year and currently stands at around 100t.
Despite that cost, there is a big win to be had – if the main dairy unit is able to grow similar amounts of forage having spread 150kg N/ha rather than 250kg N, it will result in significant long-term financial savings. There is also lots of research to show there is improved animal performance on grass clover swards.
“I am fairly hopeful when we get to year four or five we will be over the worst bit – we are in a transition phase at present,” said Patterson.
A relatively small crowd attended the clover open day at Greenmount. \ Peter Houston
Overseeding versus traditional cultivation
The preferred method used at Greenmount to establish clover is to overseed/stitch into a young and weed-free perennial ryegrass sward.
One of the main benefits is that the sward is back into the normal grazing rotation after 18 days. But to ensure new clover plants are not shaded out by grass, the swards need to be grazed every 12 to 14 days in their first year.
On the beef and sheep farm, no chemical nitrogen (N) fertiliser is used, but on the dairy unit, a half rate of around 12kg N is applied at sowing. No N is put on after the first grazing, but after that, the half rate of N is spread.
“The reduced N means there is 2 to 3t less yield in that year,” said Robert Patterson.
However, the alternative is spraying off the sward, followed by various cultivations and sowing out. In most cases that paddock is out of action for 12 to 14 weeks, so it has a major impact, especially if done in the spring.
Going forward, Patterson said if any full reseeds are required on the dairy platform, they will be done in the autumn to minimise the loss in production.
While best practice advice is for clover to be sown in spring and early summer months, a reseed at the Greenmount dairy unit last September did include clover.
A good autumn followed by a relatively mild winter allowed the clover to get established and it has been grazed three times with cows so far in 2025.
Established
Once a new clover sward is established, Patterson said it was important to get it grazed out using sheep by mid-November each year.
From spring onwards, he emphasised the need to avoid grass out-competing clover, so cows should go into swards with a cover of 2,700 to 2,800 kg dry matter per hectare (DM/ha) rather than the normal 3,000kg opening cover. “It is an 18-day rotation rather than 21 days,” he said.
Before sowing, two passes are done with a grass tine harrow to create some tilth.
Varying levels of success oversowing clover
Whether overseeding is successful in establishing clover is dependent on a number of factors, especially the weather post sowing.
At Greenmount, the aim is to overseed paddocks in the spring, however, in 2025, dry weather put a stop to that for most of May. Some moisture is necessary if clover is to get established.
Given the unpredictability of spring weather in NI, it has resulted in variable results when oversowing clover.
Adding to that are differences dependent on level of cultivation done and the machine being used.
Greenmount has utilised both an Erth and an Aitcheson drill to stitch in clover, but neither was effective in some instances.
Instead, the preferred technique is now to scarify the surface of the field with grass tines in two directions before sowing using an Einbock grass seeder, followed by rolling.
Clover is sown at a rate of 2.5kg per acre, split equally across two varieties (Buddy and AberHerald). Ideally, the sward has been cut for bales or as a minimum, it is grazed very tightly before sowing.
Weeds
While there is now a new clover-safe spray on the market in the form of ProClova, ideally any weeds should be dealt with in the previous year, suggested CAFRE adviser Trevor Alcorn.
He said soil pH should be around 6.5, with phosphorus and potassium applied based on soil analysis.
The overall aim at Greenmount is to achieve 30% white clover content in each sward, which is generally seen as the amount necessary to fix sufficient N to drive growth.
In practice, a lot of paddocks at Greenmount have had 10% clover in the first year post sowing, so the process has had to be done a second time.
“It is very difficult to go from 0 to 30% in one year with overseeding,” confirmed Robert Patterson.
The Einbock drill is used to overseed clover into existing swards at Greenmount.
A good year for red clover
In 2023, a total of 1.6ha was sown out in a red clover sward at Greenmount.
When establishing red clover, it is necessary to burn off the old sward and do a full reseed, said Robert Patterson from CAFRE.
One cut of bales was taken off during the wet autumn of 2023 and “everywhere the baler went, the clover died,” he said.
However, 2024 was different, with good-quality red clover silage made and that has carried through into the first-cut taken in 2025.
The crop is grown with no N and just slurry. The 2024 silage was offered to 12 dairy cross bullocks, with a separate pen of 12 offered grass silage. The cattle on the red clover gained an extra 0.4kg/day.
“It is not a research trial, but in our experience, the cattle hoovered it up – they loved it,” said Patterson.
Clover will help to lower GHG emissions on farms
The 124ha beef and sheep farm at Greenmount is stocked with around 100 suckler cows to beef and 210 ewes.
Total greenhouse gas (GHG) emissions on the farm are currently estimated at 1,250t carbon dioxide equivalent. However, around 15km of hedges and 5ha of woodland on the farm sequester around 308t annually, leaving net emissions at 941t.
The aim is for the farm to be 50% carbon neutral by 2050 against a 2019 baseline. Achieving that will require the adoption of new technologies as well as widespread incorporation of the likes of clover to replace chemical fertiliser use.
“Hedges and woodland are not going to make our farms carbon neutral. That is why we need to look at clovers etc. There is no easy fix to lower emissions,” suggested Dr Elizabeth Earle from CAFRE.
NUE-Leg demo at Greenmount
As part of a UK project looking at Nitrogen Use Efficiency in Legumes (NUE-Leg), a demonstration area is to be sown at Greenmount this year, forage consultant Dr Trevor Gilliland told last Thursday’s event.
NUE-Leg is a £4.7m project announced in 2024 which brings together plant breeders, research organisations and commercial companies to look at novel legume varieties. That includes the likes of improved white clover varieties resistant to drought and cold as well as red clover that would be tolerant to livestock grazing.
“You will be able to come here next summer to see the progress made,” he said.
“At the start of this project, our ambition is to take the 150kg N that can potentially be fixed by clover and double that, if not more,” added Gilliland.
SHARING OPTIONS