In 2010 Teagasc Moorepark initiated a research programme investigating the benefit of incorporating white clover into perennial ryegrass pastures for high stocking rate systems of milk production.
The results of research at the Teagasc Clonakilty Agricultural College show that incorporating white clover into ryegrass pastures has the potential to reduce costs, increase animal performance and improve environmental sustainability on Irish dairy farms.
This was the main message from a research open day, today, Tuesday, 28 June, on the Teagasc Clonakilty Agricultural College, Darrara, Clonakilty Co. Cork.
1. More grass – less fertiliser
Over three years a grass-clover system receiving 150kg of N/ha produced similar grass DM production/ha as a ryegrass only system receiving 250kg of N/ha (14.4 vs. 14.5t DM/ha respectively).
A grass-clover system receiving 250kg N/ha produced an extra 170kg DM/ha in the Moorepark study and 1,850kg DM/ha in the Clonakilty study compared to a grass-only system receiving similar N.
2. Lower winter growth
The pasture production profile of a grass-clover system is significantly different to that of a ryegrass only system; similar pasture growth rates from February to May; higher pasture growth rates from May to October and lower pasture growth rates over the winter period compared to the grass-only systems.
White clover content average 26% in the Moorepark study; 30% in the Clonakilty study; low levels in spring (<10%), increasing to a peak of 40- 50% in late summer/early autumn.
3. No effect on milk production
In the Clonakilty study perennial ryegrass ploidy had no significant effect on milk production, pasture DM production or clover content.
Animal performance has been consistently high in the grass-clover systems at similar stocking rates; +58 kg of MS/cow higher over two years in the Clonakilty study; +29 kg MS/cow over three years in the Moorepark study.
4. Lower emissions with clover
Preliminary results to-date indicate that incorporating clover into a ryegrass pasture at similar or reduced nitrogen application rates had no effect on nitrate losses to ground water; research carried out at Solohead showed that replacing fertiliser N with white clover fixed nitrogen substantially lowered nitrous oxide emissions.
5. More silage needed during the winter
The same grazing management practices developed for ryegrass pastures are equally applicable to grass-clover system.
However, during the first grazing rotation in spring at similar high stocking rates there will be a requirement for an additional 150 kg of silage DM/cow for the grass-clover system.
6. Control of weeds important
White clover can be incorporated in grassland either by direct reseeding or over-seeding using a recommended medium leaf size cultivar; it’s important that established perennial weeds are controlled prior to establishment and post-establishment using a white clover friendly herbicide to control seedling weeds.
7. Bloat problems
The incidence of bloat was associated with pastures with clover content > 60%, low sward DM content and cows with an excessively high appetite when introduced to new pasture.
In the future, Teagasc found that there will be a requirement to develop grazing strategies that avoid pastures with excessively high and low clover content.