While fertiliser prices have eased from their high point, they remain stubbornly high.

It is not surprising therefore that there is greater interest in clover swards as a means of reducing cost but still maintaining output potential.

Current studies examining the potential of incorporating clover and other forages into swards grazed by sheep were presented by Philip Creighton and Lisa McGrane, Teagasc at a Grass10 clover event held in Teagasc, Athenry, on Tuesday and have been covered in detail on these pages previously.

To recap on the main points, perennial ryegrass swards upwards of 15% clover content grew 12.9t DM/ha compared to 12.6t DM/ha in ryegrass-only treatments. This was despite the grass-only swards receiving a 55kg higher nitrogen fertiliser allocation of 145kg N/ha.

The grass-clover swards also underpinned higher animal performance with lambs finished at an average age of 186 days compared to 200 days in the grass-only treatments.

The faster-finished lambs also consumed 40% less concentrates (14kg v 8kg). The net effect is an increase in profitability of at least €100/ha.

Sowing is easy

Farmers at the event were told that sowing/incorporating clover seed is a relatively straightforward part of the task – managing swards to promote its establishment and persistency in the sward is the tricky part.

Teagasc’s Keith Fahy told farmers soil fertility is critical in getting clover established with soils requiring a pH of 6.5 ideally and index 3 for phosphorus and potassium.

The percentage of clover in a sward can appear much higher as the season progresses. \ Donal O'Leary

As regards grazing, the level of nitrogen applied should be balanced with herd-flock grass demand. Nitrogen applications should be front-loaded to promote early grass where there is lower nitrogen fixation taking place in the clover plant. An example was presented where the planned nitrogen application was at 75kg H/ha per year.

In such a scenario, the advice is to apply 20kg N/ha in February/March and April, 10kg N/ha in May, 10kg N/ha in July and 15kg N/ha in August.

Establishing grass-clover swards

The soil fertility requirements required for clover crops were already touched on above.

Where clover is incorporated as part of a reseed, the advice delivered by Damian Costello, Teagasc is to incorporate 2kg white clover seed in a 12kg mix per acre or 4kg seed for red clover. There should be a fine firm seed bed and seed should be sown at a depth of about 1.5cm followed by rolling.

The target where clover is incorporated in a reseed or over-sown is about 15% clover content.

For swards grazed by sheep, the advice is to select small leaf clover varieties. \ Philip Doyle

Where over-sowing via stitching or broadcasting seed, it is advised to use a higher seeding rate of 3kg seed per acre to allow for a lower establishment rate.

The sowing date is an important consideration where incorporating clover into an existing sward. April is the optimum month of sowing, with studies showing that May sowing reduces clover content by 5% compared to April sowing.

A blueprint presented by Teagasc to advance clover content on farms is to incorporate clover to new reseeds at a rate of about 10% per year and to over-sow approximately 15% to 20% annually.

Post-sowing management

An appropriate clover-safe post-emergence spray is important for reseeds.

The sward should be grazed tight (3.5cm) in the first grazing with the sward regrazed at about 5cm in height for the next three rotations to allow light to penetrate and prevent new seedlings from being grazed.

The crop should not be cut for silage/hay in the first year and also should be grazed later in the final rotation and earlier the following spring.

Where over-sowing, it is important to reduce nitrogen allocations for a couple of months while it will be eight to 12 months before clover is in a position to sustain similar growth and allow large reductions in nitrogen use.