For most of Robert O’Dea’s farming career, spreading one bag per acre, or even one-and-a-half bags of CAN per acre after every grazing was the norm. But things change and good farmers adapt.

So when Robert talks about spreading just seven units of nitrogen per acre now, the world doesn’t stop spinning and the grass doesn’t stop growing.

The transition to less nitrogen and more clover is one that the O’Deas are grasping with both hands.

For years, Robert milked 100 cows with his brother, Bernard, milking 65 cows next door.

In 2020, after Bernard’s son Denis returned home from college, the trio joined forces and set up a partnership.

Additional land was leased last year and the O’Deas are now milking 260 cows on a 117ha milking platform at Kilteely in Co Limerick.

Stocking rate

The stocking rate is 2.22 cows/ha with no plans to increase this any further as some of the land is heavy and may not be available for grazing in wet weather.

The O’Deas held a farm walk last week to launch the Teagasc Clover 150 group of demonstration farms across the country.

The plan at the start of the year was to spread around 150kg N/ha, back from 250kg N/ha in previous years.

Robert explains that each paddock is treated differently, depending on clover content, with the target at the start of the year for these clover fields to get 100kg N/ha and the non-clover or low-clover fields to get 200kg N/ha.

By last week, they had 56kg N/ha spread on average across the farm, which is a good bit lower than most of the other clover farmers at the walk.

Since the start of the second rotation, the good clover paddocks have been getting seven units/acre and the low or no clover paddocks have been getting double that, at 14 units/acre after grazing.

They have 16% of the farm reseeded in the last two weeks and a further 30% has just been cut for silage.

This is giving a relatively high demand for grass with a stocking rate of 4.08 cows/ha until such time as the silage ground and reseeded ground comes back in.


“Grass is tight at the moment with average farm cover at just 138kg/cow. We probably skipped over too many paddocks for silage the week before last and are playing catch-up since but we had to take them out because pre-grazing covers were too strong. In hindsight, we should probably have skipped some of the higher covers earlier,” Robert says.

Average growth rate is 70kg/ha/day and the farm looked to be growing well. It definitely didn’t appear to be suffering from a lack of nitrogen.

About 22% of the O'Dea farm has got good clover contents like this paddock.

The amount of meal being fed was increased to 3kg per cow per day to let pre-grazing yields catch up a bit.

As part of the Teagasc clover project, every paddock on the farm is measured three times per year for clover content. At present, 22% of the O’Dea farm has got high clover content and a further 10% has got some clover content, while more of the farm has been recently over-sown with clover.

Clover has also been included in the 16% of the farm that has just been reseeded so, by the end of the year, over 50% of the farm will have clover present.

According to Teagasc clover researcher Mike Egan, the over-sown paddocks and the paddocks with some clover but not yet enough clover, need to be treated as priority paddocks.

This means managing them to facilitate clover by regular grazing at low covers.

About 22% of the O'Dea farm has got good clover contents like this paddock.

Closing for silage

He suggests spreading 12 to 14 units per acre of nitrogen on these paddocks after grazing for two months after over-sowing as there is not enough clover present to replace chemical nitrogen. These fields should not be closed for silage for 12 month after over-sowing.


Cows had just left the paddock over-sown with clover and the field was very well cleaned out. A number of farmers commented that cows are cleaning out fields much better where less nitrogen has been applied.

The over-sown paddock was sown two weeks ago, using an Erth seeder which sets the seeds in slots.

Mike Egan says that this method is a bit slower to germinate because the seeds are sown that little bit deeper than with other machines.

Field that was oversown with clover two weeks ago and grazed the day before the walk.

“There’s no real difference between machines when it comes to sowing clover. The biggest failure is management after sowing. One thing we have found is that the graze out prior to sowing with a fertiliser spreader or a tine harrow and air drill combination would need to be good in order to get good seed to soil contact.

“The seeds would also need to be pressed into the ground after sowing too, either with watery slurry or by rolling.

“The second grazing after over-sowing is often the most dangerous as there is a greater risk of pulling up clover plants when cows are grazing. The slot seeders have a bit of an advantage here in that the roots are anchored into the ground a bit better,” Mike says.

The Teagasc advice is to apply a maximum of 150kg N/ha to the fields with good clover contents and a maximum of 225kg to fields with little or no clover. These rates are in addition to the nitrogen provided in slurry and soiled water.

Reducing nitrogen

According to Mike, there needs to be at least 20% clover content in July and August before nitrogen can be reduced in clover fields.

The breakdown of each application after each rotation is highlighted in Table 1. To be fair, many farmers are applying less than this and still growing good quantities of grass.

The endgame for many farmers is that nitrogen will be seen as a supplement in the same way that meal is used as a supplement now. When grass is tight, additional nitrogen can be applied and vice versa.

Bloat: tips to help prevent it

The O’Deas aren’t doing anything in particular to prevent bloat at present, but Robert said they will offer smaller breaks when cows go into fields first if they feel there is a risk of bloat. The high risk times for bloat are when:

  • Turning animals into a field of grass/clover that have not previously grazed grass/clover.
  • Grazing swards with a high clover content (greater than 40% clover).
  • Turning hungry animals into a field of grass/clover which was grazed tight in the previous round.
  • Wet morning or a dew on the grass.
  • Very lush grass, low pre-grazing yield or after grass.
  • The advice for preventing bloat is:

  • Keep post-grazing height at 4cm.
  • Avoid turning hungry cows into grass/clover fields.
  • Give bloat oil in the water supply.
  • Provide a small area of the paddock for the first few hours of grazing – a breakfast break. This will encourage cows to graze down hard and increase fibre intake.
  • Identify high-risk paddocks and monitor cows closely when grazing these.
  • There are two ways of treating cows with bloat. Unfortunately, many farmers don’t ever get to treat a cow as the first sign of a problem is a dead cow. Speed is critical as cows can die quickly after developing bloat.

    Bloat oil or paraffin oil can be given down the neck at a dose rate of 60ml to 100ml. This oil will help to displace the froth buildup in the rumen.

    In severe cases, the rumen may need to be punctured in order to release the gas.

    This should be done using a trocar and canula but where not available a very sharp knife will also work. Looking at the cow from behind, identify the triangle area between her last rib and the hip bone. Puncture the cow close to the centre of this triangle.

  • O’Dea partnership milking 260 cows at Kilteely in Co Limerick.
  • Big emphasis on incorporating clover and reducing nitrogen usage.
  • New Teagasc Clover 150 group established with the aim of having 50 farmers demonstrating low nitrogen usage around the country.
  • The O’Deas are spreading seven units of nitrogen per acre after grazing on the good clover paddocks and 14 units/acre on the low clover paddocks.