Farm Ireland

Saturday 21 April 2018

Trials that could put farmers in the clover

New Teagasc research suggest that maximising clover growth could substantially increase dairy incomes

Boost: The Teagasc trail in Clonakilty reports that cows grazing swards clover incorporated have yielded an extra 55 kg/ha of milk solids
Boost: The Teagasc trail in Clonakilty reports that cows grazing swards clover incorporated have yielded an extra 55 kg/ha of milk solids
Darragh McCullough

Darragh McCullough

Clover has the potential to earn farmers millions extra from their farms if the early results from Teagasc research are maintained.

While the research, which is being conducted simultaneously with a 60 cow herd at Moorepark and 120 cows in Clonakilty, is on-going, it shows that clover swards have the potential to increase milk solid yields up to €500/ha.

Deirdre Hennessy and Brian McCarthy are the two lead researchers on the trials, and while they are cautiously optimistic about the potential of the age-old plant, they admit that farmers remain cautious about adopting clover into their systems.

"It gets a mixed reaction to be honest," said Dr McCarthy. "A lot of the farmers that have experience of using clover in the sward went away from it because it kept dying out of the swards. That has made them wary, and even though the results so far are quite good, most guys are telling me that they are going to sit out the duration of the trial to see if it pans out the same way after five years."

But the results so far are hard to ignore. The cows grazing the swards with clover incorporated in Clonakilty have yielded an extra 55 kg/ha of milk solids (MS), while the cows on the grass-clover mix in Moorepark gave an extra 33kgMS/ha. At stocking rates of close to 2.75 cows per hectare, it results in an extra 100-150kgMS/ha.

The value of milk solids can vary, but at €4.50/kg, this is worth €450-675/ha, a colossal difference for very little outlay. Clover seed costs something like €10/kg, and seeding rates tend to be about 5kg/ha.

In Clonakilty the clover mix produced an extra 2.5t/ha of drymatter over the 100pc ryegrass swards. However, in Moorepark, there has been no increase in herbage production.

The researchers believe the lift associated with the inclusion of clover in the sward was bigger in Clonakilty because the soil fertility is slightly lower at this site.

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"The Clonakilty site was used as both tillage and silage ground for many years before this trial was established, so the inherent fertility is lower than in Moorepark where the pastures have been grazed intensively for years," said Dr Hennessy. However, there are three key issues that the researchers need to overcome before clover inclusion can be recommended for farmers - persistancy, lower growth-rates in spring, and bloat.

White clover's unique characteristic in grazing swards is its ability to 'fix' or harness atmospheric nitrogen - a vital trait as agriculture tries to mitigate its greenhouse gas emissions.

Its productivity falls when temperatures fall below 10C, explaining why grass produces more in the spring. Conversely, it produces more than grass at temperatures of more than 20C.

This ensures its peak is approximately one month later than grasses May-June peak. Its palatability is also higher than grass, ensuring excellent utilisation by grazing cows.

A total reseed is the best approach’

One of the challenges of switching to a grass-clover system is getting the clover established.

Full reseeding is the best option to get a good clover establishment, but clover can also be sown into existing swards.

However, there is an increased  risk of bloat for cows if they are chopping and changing between paddocks with a high clover content and ones that are dominated by grass.

Brian McCarthy believes that a complete reseed is the best way to get clover established in the swards initially.

“A total reseed is the best way to get clover going, but it  is possible to top up on the clover content by simply broadcasting seed with a fertiliser spreader.

“You need to make sure that the pasture is really well grazed out so that it is as open as possible. The ideal is after a cut of silage because that means the grass will be that bit slower getting going again. But it will also need 25-50kg/ac of 0:10:20 and maybe 2,000gal of watery slurry,” he said.

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