Organic Forage Seed Production

B Boelt

Danish Institute of Agricultural Sciences, Department of Plant biology

DK-4200 Slagelse


From January 2004 only organically produced seed can be used in organic farming systems within the EU. Optimal forage production relies on the access to improved cultivars of high quality clover and grass seed for forage mixtures. Currently the supply of organic forage seed in Europe is scarce. In Denmark a production of one of the main constituents of forage mixtures, perennial ryegrass (Lolium perenne L.) is established, however, another main constituent, white clover (Trifolium repens L.) is still in request.

In general seed yield in organic production is decreased compared to conventional production. In perennial ryegrass the seed yield reduction is approximately 25% whereas it similarly are 80% in white clover. Until now research initiatives has not been able to increase seed yields in white clover, whereas organic grass seed production in general are performed without larger difficulties. Currently the European Commission has put forward a proposal allowing derogations to use conventional grown seed if organic varieties are not available in species that will not be listed in an annex to the regulation.


EU regulation 2092/91 states that only organically produced seed can be used in organic farming systems. However, due to insufficient supply of organic seed, derogations have made it possible to use conventionally grown seed if no organic seed are available. The present derogation states a deadline of 1 January 2004 for the implementation of the EU regulation 2092/91.

The organic sector wishes to use organic seed in order to close the production chain and for credibility and transparency to the consumers. Organic farmers need a divers range of varieties and well-adapted varieties to optimise the organic farming system. Organic forage production for ruminants in Northern European farming systems is based on mixtures of various grass and clover species with main constituents being perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.). To obtain a high degree of on farm produced forage the composition of these mixtures must be optimised in relation to soil conditions, climate, and end products (grazing, silage and haymaking). To fulfil these demands the natural properties of various species must be utilised (preference for soil type, nutrient utilisation, and growth rhythm). Forage plant breeders are continuously releasing improved cultivars in terms of quality, palatability, resistance and yield. Optimal ruminant production and welfare are only reached when the organic grower has access to the full range of improved varieties and diverse species.

Organic Forage Seed Production in Denmark

Since 1992 an organic forage seed production has been established in Denmark (Lund-Kristensen et al., 2000), and in 2002 the production area was approximately 1600 ha for grass and 800 ha for clover seed. Organic forage seed is an interesting crop for the organic farmers in Denmark. The majority of organic farmers in Denmark are dairy farmers, and the production of ryegrass seed suits quite well at these farms. They have access to nutrients (animal manure) and they can utilise secondary products such as the straw and autumn regrowth for feed. A typical crop rotation with organic grass seed production is shown in table 1. Recently larger arable farms have converted to organic production. To them interest in organic forage seed production is often driven by the need to grow crops with a low export of nutrients or crops, which in fact ‘import’ nutrients such as legumes and clovers. A typical crop rotation with organic clover seed production is shown in table 1.

Table 1. Crop rotations including grass and clover seed production in organic farming systems in Denmark.

Organic grass seed production / Organic clover seed production
Spring cereal, cover crop / Spring cereal, cover crop
Grass seed / Clover seed
Field pea / Winter or spring wheat
Winter or spring wheat / Spring cereal
Pulses (lupins or field bean) / Field pea

In general high seed yields in organic grass seed production are obtained whereas clover seed yields are considerably lower than in conventional production (table 2).

Table 2. Seed yield in perennial ryegrass and white clover average of 2001-2002 in organic and conventional production (personal communication).

Seed yield (kg ha-1) organic production / Seed yield (kg ha-1) conventional production
Perennial ryegrass, 4N / 1051 / 1396
Perennial ryegrass, 2N / 787 / 1041
White clover / 90 / 478

In tetraploid and diploid perennial ryegrass seed yield in organic production was decreased by approximately 25% compared to conventional production. However, it should be noted that the results from conventional production also include amenity types, which normally have a lower seed yield. The results from organic production are primarily based on forage types. In white clover seed yield in organic production was decreased by approximately 80% compared to conventional production.

Research Activities

At the Danish Institute of Agricultural sciences research activities are carried out with the objective to develop and optimise cultivation and management techniques in order to increase the production of high quality grass and clover seed for forage mixtures (Boelt, 2002).

Recent research has focused on establishment techniques that allow for mechanical weed control. In perennial ryegrass it has been shown that when the seed crop is sown in the cereal-row plant density is decreased, however, seed yield has been almost equivalent to sowing between cereal-rows. When the seed crop is sown in the cereal-row, cereal plants protect the young grass plants during mechanical weed control. In table 3 are shown the effect on seed yield in perennial ryegrass of various strategies for mechanical weed control.

Table 3. The effect of mechanical weed control in a spring barley cover crop on yield in an undersown perennial ryegrass seed crop. Average of 2000 and 2001.

a. Barley 3-4 leaves, b. Barley 3-4 leaves and at tillering.

Average 2000 and 200
(kg ha-1)
a. / b.
/ Blind harrowing / 1619 / 1677
/ Untreated / 1772 / 1771
/ Untreated (sown between cereal rows) / 1635 / 1625
/ 1 harrowings / 1606 / 1711
/ 2 harrowings / 1668 / 1661
/ 3 harrowings / 1642 / 1701
/ 1 hoeing / 1671 / 1690
/ 2 hoeings / 1717 / 1666
LSDP<0.05 / 149 / 142

There were no significant difference between the different treatment strategies an in general seed yield was not reduced compared to untreated (sown between cereal rows). Except for treatment 3 all plots were established with the grass seed crop established in the cereal row at 24 cm row spacing. This might explain why no yield reduction is in contrast with results of (Borm, 1995).

One of the most essential problems in organic seed production on arable farms in Denmark is inadequate nutrient supply. Besides the total amount of nitrogen, seed crops are also very sensitive to the timing of nitrogen application. Correct timing will stimulate reproductive development whereas excessive and poorly timed nitrogen application will be in favour of vegetative growth. If a nitrogen-fixating pre-crop provides nutrients, the grass seed crop will take up nitrogen as soon as it is mineralised which will most likely lead to excessive vegetative growth. Mixed cropping of a grass seed and a green manure crop provides an option on timing the nitrogen release (Gislum et al., 2003). In a field experiment Aamlid (2002) have shown that high timothy seed yields may be obtained without nutrient application, when the timothy is grown together with different clover crops. The intercropping with green manure crops may also provide the opportunity to utilize forage cuts as a by-product in organic grass seed production (Deleuran et al. 2002).

Yields in organic white clover seed production are reduced by approximately 80% compared to conventional production. Research activities have been established, however, for the moment the problem of clover seed weevils are not solved. A survey in organic clover seed fields have shown that weevils are found in all organic white clover fields, that the yield reduction from these range from the weevil larvae may be 12 – 77%. The amount of un-pollinated flowers was in general low. It is therefore assumed that other factors than damage by pest are causing the low yields. Currently research activities are continued.

Future Development

Due to intensive advisory support the requirement of the Danish home market for organic perennial ryegrass seed was already fulfilled in 2000 and export to other European countries are under establishment. In organic grass seed production relatively high yields are obtained. Organic growers find this production very interesting, and it is assumed, that it is possible to increase the production area if a higher demand for organic grass seed will develop in future. In organic white clover seed production, on the contrary, yields are very low and at present it is not possible to fulfil the demand of the Danish home market. However, growers are still interested in this production since the clover seed field function as a green manure crop.

The future development with regards to organic seed production is highly influenced by the EU-legislation and possible derogations to use conventional seed in organic production. Currently a proposal has been put forward allowing derogations to use conventional grown seed if organic varieties are not available in species that will not be listed in an annex to the regulation. This annex has not been prepared yet. A prerequisite is that national databases of available organic seed are established in each EU-member state. After a two-year period the availability of organic seed will be evaluated, and the European commission will consider establishing a common European database.

Currently a national database is running in Denmark ( and a common database administered by FiBL, Research Institute of Organic Agriculture (


Aamlid, T.S. Yield and Quality of Mixed Seed Crops of timothy (Phleum pratense) and Clovers (Trifollium spp.) in an organic cropping system. Acta Agriculturae Scandinavica 52:18-24.

Boelt, B., Deleuran, L. C. & Gislum, R. 2002. Organic forage seed production in Denmark. Newsletter, The International Herbage Seed Production Research Group no. 34:3-5.

Borm, G.E.L. 1995. Possibilities of Mechanical Weed Control at Different Row Distances in Perennial Ryegrass grown for Seed. Proceedings of the third International Herbage Seed conference, Germany, 1995:271-275.

Deleuran, L. C. & Boelt, B. 2001. Forage Cuts as a By-product in Organic Seed Production. Newsletter, The International Herbage Seed Production Research Group no. 34:5-7.

Deleuran, L. C. & Boelt, B. 2000. Utilization of forage cuts in organic grass seed production. Proceedings of the 18th General Meeting of the European Grassland Federation Aalborg, Denmark. p. 552-555.

Gislum, R., Jensen, E. S., Boelt, B. & Wollenweber, B. 2003. Intercropped green manure legumes in perennial ryegrass (Lolium perenne L.) for seed production. In: Dynamics of Nitrogen Use Efficiency in Grass Seed Crops. Ph.D. Disssertation. The royal Veterinary and Agricultural University, Copenhagen. 102pp.

Lund-Kristensen, J., Jensen, M.T. & Grønbæk, O. 2000. Organic production of grass and clover seed in Denmark – a new challenge to the seed industry. Proceedings of the 18th general Meeting of the European Grassland Federation, Denmark. 539-541.