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White Clover on Organic Farms

18 April 2020
Type Media Article

ORGANICS: Research has shown that in a productive sward white clover can supply 100-150Kg Nitrogen/ha/year. Find out how to get it established in pastures.

The growing and management of grassland is a normal practice on all farms. There is however a difference as regards the supply of Nitrogen (N) for grass growth on organic farms, with soluble mineral fertilisers prohibited. Organic farmers have to look at alternative nitrogen sources, one of which is home grown nitrogen in the form of white clover.

Clover has the ability to ‘fix’ nitrogen from the atmosphere and is one of the key ways for an organic farmer to get nitrogen into the soil. Research has shown that in a productive sward white clover can supply 100-150Kg Nitrogen/ha/year.

In this video, Dr James Humphreys, Teagasc gives an overview as to why a farmer should grow white clover.

Methods of establishing white clover in pastures

Plough and Reseed.

This is the most reliable method of establishing clover.  As the seeds are small, a firm, fine seedbed is essential to ensure close contact between the soil and seed. A light harrowing and firm roll will ensure that the seed is in close contact with the soil, it also presses down stones and helps retain soil moisture. The grass/clover seed mixture can be under-sown into a cereal crop or arable silage crop in the spring or sown directly in spring or autumn.

Minimum Cultivation

One method of doing this is to take a close cut silage crop off the field immediately prior to reseeding. Cutting the sward close to the soil surface slows the regrowth of the existing sward.  Liming improves the chances of success as it neutralises acidic conditions due to the decay of the old sward.  After the silage is removed, the soil can be tilled with power machinery.  The seeds could also be drilled directly into the soil. In this case ensure that the seed is not buried too deep (<1cm depth)

Broadcasting/Surface Seeding/Over-sowing

Broadcasting clover seed into existing pastures, offers a cheaper method with a 75% success rate at farm level. The level of success will depend on the following conditions;

  • Presence of bare ground after a tight graze or cut. For successful establishment there must be contact between the seed and the soil.
  • Use of 5kg of clover seed per hectare.
  • Lightly roll after sowing to ensure seed soil contact.
  • Graze regularly after sowing in order to prevent the existing sward from competing with the new seedlings.

General Guidelines for Clover Establishment

White clover seeds are tiny with very small energy levels. Because of this, regardless of the method used for clover establishment, the following principles must be followed

  • A warm soil and sufficient moisture are necessary for seed The optimum time for sowing is from early April to the end of May and from mid-July to mid-August.
  • Seeds should not be sown deeper than 1cm in depth.
  • Contact with soil is essential for seed establishment.
  • Soil testing is important, especially after ploughing, as a pH of 6.0-7.0 and phosphorus levels at between 3.1ppm and 8.0ppm are necessary for successful establishment.
  • Pelleted conventional seed is not permitted to be used. Organically certified organic grass/clover seed should be used. Where such seed is unavailable a derogation for the use of untreated non-organic seeds must be sought from the Organic Certification Body.

 For more information go to www.teagasc.ie/organics