The clover trial in Clonakilty is pushing the boundaries on getting the most from grass-based systems for less.

At a high level, the trial is comparing cows grazing mixed clover and grass swards with cows grazing grass swards only. The cows on the mixed clover grass swards last year delivered 58kg more milk solids per cow. At €5/kg of milk solids, that’s almost €300 per cow more revenue while at €3/kg milk solids, it is €175 per cow more revenue. However, the trial results show not only is there more milk produced per cow, but there is also more dry matter grown per hectare.

The mixed clover grass swards are growing almost 2t more grass per year. Brian McCarthy explained that there is less clover around this year so far but, in the last week, it is beginning to take off again. Brian said: “We are in year four of the trial and there is about 10% less clover in the swards this spring compared with last year, but the real differences in production and grass yields don’t normally come until the second half of the year anyway.”

The reasons for less clover in the swards this year are not clear, but it was a colder and later spring which reduced temperatures and subsequently reduced growth rates. However, the natural clover slide off could also be an issue and maybe by year four since establishment, it is time to start renewing paddocks with clover seed again. The fact that 250kg of bag nitrogen per hectare is being spread is probably not helping the clover plant either but that will continue for the duration of the trial.

So the upside is big, very big in fact, and far exceeding what some other technologies can deliver. However, with a big upside come challenges and the Clonakilty staff have had to learn as they go on how to manage.

Bloat

Bloat is a key challenge and farm manager Fergal Coughlan explained that they now know the paddocks bloat will hit. The key is to get bloat oil into cows the day before they go into that paddock. In the second half of the grazing year, Fergal uses a five-litre drum with a dribble release that gradually lets bloat oil into water troughs.

So far this year, he has only used this once, but he is likely to use it a lot more in coming weeks and months as there will be more clover in swards.

The other challenge is the spring feed gap – clover swards have less growth and cover when it is cold.

Over winter, the grass-only swards grew 5kg per day compared with just over 1.5kg per day for the grass clover swards. So, on the farm with mixed swards, Fergal had a cover of 800kg starting off compared with an average cover of 1,000kg on the grass-only swards.

Fergal showed that they filled the gap with quality round-baled silage rather than extra meal.

Managing clover grass swards

  • Top-class grassland management is key. You need to keep pre-grazing covers low (less than 1,400kg) and graze out properly (post grazing 3cm to 4cm).
  • Soil fertility is key – if the pH is not 6.3 or above, clover will struggle – phosphorus and potassium are also key, so that the annual soil fertility plan is essential.
  • Spring will be challenging, but early nitrogen and early grazing will help clover later in year.
  • Restrict allocation (put up a strip wire) if letting cows into a paddock with over 50% clover – it restricts cows from selecting clover only.
  • Don’t take heavy silage crops if you could end up with too much clover – alternate what paddocks are taken, even for light silage crops.
  • The more grazing you can do rather than relying on silage will help to control clover.

    • Establishing clover in existing swards

  • Over-sowing after second cut or light cut of silage is ideal – late spring early summer is perfect.
  • When over-sowing, you should use between 3kg and 5kg of clover seed per hectare.
  • You need soil-to-seed contact, so light slurry after spreading clover seed can help.
  • If including clover into the new reseed, then 2.5kg of seed per hectare is plenty – no more clover will be established if you go with more clover seed.
  • The first three grazings are critical – graze at a low cover to allow clover get established.
  • Weed control is important and clover-safe sprays are not as strong as other sprays, so you need to spray when weeds are young.
  • Often, a second weed spray might be needed.

    • The Clonakilty Agricultural College farm is growing serious volumes of grass – close to 17t in the last two years. Prior to this trial, the farm was coming from a tillage history and big cuts of silage, so it is fair to say that background nitrogen in the soils was probably depleted. This could go some way to explaining the excellent responses to clover in the swards. Yes, there are challenges with managing and establishing clover but it is trials like this that help better understanding.

    The Clonakilty staff are clear that they are learning more and more each year and they are confident that managing bloat and mixed clover swards is not as big a challenge as it was in the past.

    The key for the researchers involved now is to move the measurement and management of these mixed clover swards on to commercial farms. In the past, many farmers have tried to establish clover or manage clover and, for one reason or another, they have moved away from clover.

    The financial benefits of these mixed swards must not be overlooked but, at the same time, we need to move these results out on to different soil types, different weather patterns and varying farm management. I understand this has started to some extent and the sooner results start to flow, the better. There are lessons in this trial for all farmers – beef and sheep farmers included – and not only dairy farmers.