As farmers across the country try to tackle high fertiliser prices and find ways of reducing spend, they will look to crops that could help cut those costs, while providing high yields and feeding value.

James Humphreys spoke about managing red clover on dairy farms on a Signpost series webinar last week.

He was clear that red clover is a good option for silage production on out-blocks.

With the potential to get three cuts of silage, plus grazing and no need for nitrogen (N) fertiliser, it can cut costs and work load.

Matching yields of PRG

Research carried out at Teagasc Grange from 2002 to 2007 compared a red clover and perennial ryegrass (PRG) sward which did not receive any fertiliser N with a PRG-only sward which received 600kg N/ha to ensure that N was not a limiting factor in production. James noted the high level of herbage production in the red clover sward relative to the PRG sward consistently over the six years.

He explained that the clover showed good persistency and while there was a decline in red clover content over time, the crop remained productive due to a build-up of fertility.

Over the six year trial, the red clover grew an average of 14.9t DM/ha/year, compared to 14.8t DM/ha/year on the PRG sward with unlimited nitrogen.

Sowing

James recommends a full reseed ahead of red clover, to give the crop the best chance against weeds, particularly docks. Soil pH needs to be at 6.5 and the crop has a high K requirement.

If K is inadequate in the soil, it can shorten the longevity of a sward. However, the crop will also take up luxury K, so caution is needed as there is a risk of milk fever where this is not managed correctly.

He commented that a 15t DM/ha crop will need 375kg K/ha/year. For example, at Index 1 for K, 25kg of K and 3kg of P is needed per tonne of dry matter produced. If 5t is taken off in the first cut, that’s 125kg K/ha and 15kg P/ha.

James also cautioned that a four-year break is needed between crops to avoid infestation by the stem eelworm, while sclerotinia can also be a risk, but is a low risk in Ireland at present.

Suggested seeding rates can be seen in Table 1.

James recommended looking at the Northern Ireland recommended list from 2016 and the 2020/2021 list for England and Wales for variety choice. Fearga, Milvus, AberClaret, AberChianti, Lemmon, Merviot and Amos were mentioned as varieties to watch out for.

Silage production

The target for the first cut of silage should be mid-May and every six or seven weeks after this time. Farmers can expect three good cuts of silage and can graze or zero-graze in October or November. James noted that red clover silage is more difficult to ensile, as it needs to wilt properly.

At Solohead research farm, the aim is to wilt for 48 hours. Getting this length of a wilt on a third cut is risky, James explained, adding that getting this wilt on a fourth cut is almost impossible and grazing is the best option here. Where a proper wilt cannot be achieved, an effective preservative should be used.

Strengths

  • Very high N fixation and so lower fertiliser N costs.
  • High-yielding silage on out-blocks.
  • Can help to reach fertiliser reduction targets.
  • Lower carbon footprint.
  • Lower ammonia emissions.
  • Very low nitrate leaching under cut and carry.
  • Can be included in grazing swards.
  • Weaknesses

  • Poor persistency (three to four year sward).
  • Comes with costs and risks associated with reseeding.
  • Silage production requires greater attention.
  • Dock control can be difficult.
  • Risk of stem eelworm and sclerotinia.
  • High phyto-oestrogen content (can affect sheep in the breeding season).
  • Risk of bloat undergrazing.