As part of ita ZeroNsile project, AgriSearch recently held a farm walk on red clover establishment on the farm of Francis McDonnell near Dromore, Co. Tyrone.
McDonnell farms 50 dairy cows which are milked on a robot and grazed for 12 hours per day during the summer months.
He is a relatively new entrant to dairying having started milking in 2018 after converting from a suckler herd.
McDonnell works full time in IT and is farming 110acres with 41 cows currently milking and 9 dry cows. All cows purchased privately at the moment; however, the plan is to use sexed semen into the future.
Cows are currently producing 28.8kg of milk/day, with 4.41% butterfat and 3.39% protein and a somatic cell count of 144,000 cells/ml.
With the cows currently undergoing 2.8 milkings per day, their predicted annual yield is 7,800L/cow.
Cows are allocated 12-hour grazing blocks from 2:00a.m. to 2:00p.m. and McDonnell is now into his third rotation, with the ground receiving two bags of 17:4:4/ac to date with slurry in the spring.
Red clover
The ZeroNsile project was established in 2023 to examine the feasibility and practicalities of producing silage without the use of manufactured N fertiliser, focusing primarily on red clover swards.
McDonnell selected a sward mix that suited his heavy soil conditions – it included a high proportion of Timothy and late varieties of perennial ryegrass alongside both red and white clover.
The importance of having the right soil pH when establishing red clover was highlighted. AgriSearch’s agriculture manager John Morrow said that farmers should target a pH of 6.5 before sowing.
Morrow also highlighted the importance of getting nutrient management right, noting that on many farms, slurry on its own was insufficient to meet the potash (K) requirements.
Morrow said: “It is important to plan this in advance as zero N fertilisers are not readily available from merchants at short notice.”
David Linton from Barenbrug said that caution needs to be exercised if tedding red clover, as leaf shatter can be an issue, which needs to be avoided as most of the protein is located in the clover leaf.
He also recommended that the crop should also be allowed to flower once per year and the sward should not be cut too low when mowing.
Project
A total of 12 farms were selected to trial red clover silage swards. The swards were established during autumn 2023 and spring/summer 2024, which resulted in similar yields and quality between grass and red clover in 2024.
These results were impressive, as red clover swards received 2.3 times less N, even though 2024 was a challenging year for clover.
The project on McDonnell’s farm consisted of a 2.545ha field soil sampled prior to being sprayed off for weeds – mainly docks.
It was then covered with farmyard manure and slurry, and limed at 2.5t/ha in late 2023. A field with no red clover sown received the same.
The red clover sward was sown on June 26, 2024 and it received one light application of slurry of about 1,000gals/ac. It was mowed on September 1 – which was a light crop to just tidy it up, getting 21 bales from it.
In 2025, the red clover field and grass-only field received 2,500gal/ac of slurry in early March. The grass-only field received two bags of 27:4:4 + sulphur (S)/ac at the end of March.
On May 9, both fields were cut and harvested 24 hours later. Both yielded the same 3 .5t dry matter (DM)/ha, accumulating to nearly 6.5 bales/ac.
On May 16, the red clover paddock received 3,000gals/ac of slurry only, while the grass paddock received 2,000gals/ac of slurry, which was followed by 2.5 bags of 27:4:4 +S/ac after the slurry.
Some farmers’ reviews of their finding included the following:
- “It can be slow in cold/wet spring compared to grass”;
- “It feeds better than it tests”;
- “It’s difficult to get a nutrient balance right with slurry alone”;
- “Needs to flower once a year, don’t roll or scalp when mowing”.
