Does clover work in Cavan soils?

For the last three years, researchers at Ballyhaise Agricultural College have been experimenting with getting clover established across the dairy research farm.

Up to now, research on clover has been concentrated on the drier soil types in the south of the country; at Clonakilty and Moorepark in Cork and Solohead in Tipperary.

The five-year study at Ballyhaise was set up in 2021 to see if clover can make similar contributions to on-farm performance on heavier type soils in the northern part of the country. Effectively, the project is in two parts – the establishment phase and the implementation phase.

The study compares animal and grass performance on perennial ryegrass only and perennial ryegrass and white clover swards at 250kg N/ha and 125kg N/ha respectively for the grass only and grass/clover swards.

Prior to 2021, the swards at the dairy unit at Ballyhaise were predominately perennial ryegrass so the first phase of the project has been to convert the swards to perennial ryegrass and white clover. Researcher Donal Patton says that the decision was made to fast-track this process in order to get as much clover established as quickly as possible.

By the end of 2023, half of the experimental area was in grass/clover and the other half in grass only.

Full reseeding

Donal says that the clover was established through a combination of full reseeding and oversowing. In 2021, 30% of the area was reseeded and a further 20% was oversown. In year two, 20% was reseeded and another 20% oversown and in 2023, which was the third year of the study, another 30% was reseeded.

“We really fast-tracked getting clover established by doing so much reseeding and oversowing in such a short space of time. We did so to really test the clover in Ballyhaise but it’s not something we would be recommending to commercial farmers as it had a big negative impact on grass growth and the amount of winter feed we made during the establishment phase,” Donal says.

Importantly, Donal points out that the amount of land reseeded in the grass/clover treatments was replicated in the grass-only treatments. He says this was done to ensure that there was no bias given to the grass/clover swards when comparing performance.

Nitrogen

In terms of nitrogen, the researchers adopted a technical approach to deciding when to reduce N fertiliser inputs. All of the area was treated the same in terms of N rates up to May each year. How much nitrogen to reduce by in the grass/clover swards is decided on a paddock-by-paddock basis.

If there is 15% or more clover in the sward in early May, then that field gets no more chemical nitrogen for the remainder of the season. However, where clover contents ranged from 0% to 5% in early May there was no reduction in chemical nitrogen. Where clover contents ranged from 5% to 15%, chemical nitrogen was reduced by 50% compared to the rate being applied to the grass-only treatment.

Over the first three years clover content was highest in the reseeded fields, with an average of 30% clover content compared to 14% in the oversown swards. Donal says that clover contents should be over 20% to replace chemical N fertiliser without implications for pasture production.

Across the establishment phase of the project the average pasture production, not including the establishment year, was 14.48t DM/ha on the grass swards with 245kg N/ha and 14.6t DM/ha on the clover swards with 105kg N/ha.

Over the course of the three years, there was no real difference in animal performance between the treatments.

The cows on the grass-only swards produced 461kg MS/cow from 840kg/meal per cow while the cows on the grass/clover swards produced 473kg MS/cow from 848kg/meal per cow.

Donal says that the differences in animal and grass performance should become more apparent from now on as the clover contents get higher.

By the end of last year, over 52% of the grass/clover area had sufficient clover to reduce N applications by 140kg N/ha.

The researchers are holding an open day on the farm on Wednesday 24 July at 10am where the lessons encountered during the establishment phase and expectations from the next phase will be discussed.