ANIMAL MANURE OR COMPANION CROPPING WITH HERBAGE LEGUMES AS NITROGEN SOURCES IN ORGANIC SEED PRODUCTION OF TIMOTHY (PHLEUM PRATENSE) AND MEADOW FESCUE (FESTUCA PRATENSIS)
Organic seed crops of timothy (Phleum pratense) ‘Grindstad’ and meadow fescue (Festuca pratensis) ‘Fure’ were sown in pure stand or with a companion crop of white clover (Trifolium repens) ‘Milkanova’ (6 kg grass seed + 1 kg clover seed ha-1) in six trials with a total of 15 (timothy) or 12 (meadow fescue) harvests from 1999 to 2001. In the ley years, crops received 0, 30 og 60 kg ha-1 of total nitrogen (tot-N) in cattle slurry or dried chicken manure. Due to competition from white clover, first year seed yields were lower on plots sown with than on plots sown without white clover. Although this was partly compensated in the second and third ley year, the total grass seed yield over the ley period was not higher from mixed than from pure crops. Furthermore, contamination of clover seed, either from sown or voluntary plants, complicated certification of timothy seed lots in the first and, in most cases, second ley year. Optimal inputs of manure to seed crops of timothy and meadow fescue were, in turn, 30 and 0 kg tot-N ha-1 in the first ley year, 60 and 30 kg tot-N ha-1 in the second ley year, and 60 and 60 kg tot-N ha-1 in the third ley year. Higher inputs of manure decreased the occurrence of white clover, but interactions between sowing with or without white clover and manure inputs were mostly insignificant.
In a series of still on-going trials (2002-2005), promising results have been obtained with the establishment of organic timothy seed crops with a companion crop of subterranean clover (T. subterraneum). Besides fixing nitrogen, this large-seeded and short-lived legume provides competition against weeds (including voluntary white clover and alsike clover) in the sowing year.