The benefit of clover in grassland has previously been reported through increased animal performance, increased grass production and potential saving in chemical nitrogen (N) fertiliser, as well as improving N use efficiency and N farmgate surplus.

Soil fertility is a crucial factor in establishing and maintaining adequate clover on farm.

When selecting clover varieties to sow, use the Department of Agriculture recommended list.

Small- and medium-leaved cultivars are best suited to intensive grazing systems, with large leaf clovers more suited to silage-based systems.

Clover should be sown ideally when soils are warm and moist – ideally in late April/ May, with over-sowing only to be done in April/early May.

Establishing white clover on farm will take some time, using a combination of both reseeding and over-sowing. Incorporating white clover in a full reseed is the most reliable method of clover establishment.

Over-sowing is a simple and low-cost method of introducing white clover into swards. Success is very much dependent on soil fertility, weather conditions at over-sowing and post-sowing grazing management.

White clover establishment

A targeted multi-year approach should be used in establishing a white clover system – a combination of reseeding and over-sowing.

  • Reseed 8% to 10% per year.
  • Over-sow approximately 20 % per year.

    • – year one: reseed 10% and over-sow 15% = 25%.

    – year two: reseed 10% and over-sow 15% = 25% (50%).

    – year three: reseed 10% and over-sow 15% = 25% (75%).

    – year four: reseed 10% and over-sow 15% = 25% (100%).

    – year five +: ongoing process.

    Reseeding

  • Spring reseed provides best results –April, May.
  • Spray off the old pasture with glyphosate.
  • Prepare a fine, firm seedbed (with the most appropriate cultivar method for that paddock).
  • Soil sample and apply required lime, P and K – apply as per soil result.
  • Use the Irish recommended list for grass and clover cultivar selection.

    • – medium-leaf cultivars for cattle swards.

    – small-leaf cultivars for sheep swards.

  • Sowing rates

    • – Cattle: 28-30kg/ha (grass); 4-5kg/ha (white clover).

    – Sheep: 25-28kg/ha (grass); 5-6kg/ha (white clover).

  • Ensure good seed: soil contact by rolling after sowing.
  • Nitrogen fertiliser post-sowing is important to ensure an adequate balance of grass/clover in the sward – applying zero nitrogen post-sowing can result in clover dominant swards (increases risk of bloat).

    • Over-sowing

  • Control weeds the previous year prior to over-sowing white clover.
  • April/early May is the best month for over-sowing.
  • Over-sow directly after a tight grazing.
  • White clover can be over-sown in a number of methods.
  • Ensuring soil contact post over-sowing is one of the most crucial factors.
  • White clover seed can be broadcast on to the sward or stitched in using a suitable machine.
  • If broadcasting with a fertiliser spreader:

    • – Mix clover seed with 0:7:30 fertiliser and only add white clover to the spreader when you are in the field to avoid white clover settling at the base of the spreader, with a maximum of 1ha at a time.

  • Stitching in white clover seed with a drill/harrow ensures better seed-to-soil contact.

    • – Stitching must be used for over-sowing sheep grazed swards due to the denser nature of swards.

  • Sow at a rate of 5kg to 6kg/ha.
  • Reduce N fertiliser post over-sowing to 15kg N/ha per month (12 units N/acre) for two months.

    • Post-sowing management – (full reseed or over-sowing)

  • Having light available to the base of the sward is a crucial factor in post-management. This encourages taproot and stolon development.
  • The first grazing should be at a pre-grazing herbage mass of 600kg to 1,000kg DM/ha.
  • Subsequent three grazings should be at a pre-grazing herbage mass <1,100 kg DM and graze swards to =4cm (graze tight) – this will mean that paddock grazing times will be much reduced in these paddocks.
  • No silage in the first 12 months after establishing.
  • Swards should be grazed later in the autumn to avoid carrying heavy covers over the winter.

    • Post-emergence spray for weed control is essential.

    Weed control

    Weed control in reseeded and over-sown grass-white clover swards is vital to improve sward persistence. Clover-safe herbicides should be used in establishing and established swards.

    All pesticide users should comply with the regulations as outlined in the Sustainable Use Directive.

    Reseeds

  • Weeds are best controlled when the grass plant is at the three-leaf stage and the clover when the trifoliate leaf has appeared. White clover-safe herbicide should be used.
  • Pro-Clova will be the only licensed clover-safe herbicide available for new reseeds.

    • – Eagle and Pro-Clova are both licensed for established swards.

    Over-sown

  • Established weeds should be controlled the previous year before over-sowing.
  • Consider the residue time of non-clover safe sprays (this may affect clover establishment – read product label).