What are the limiting factors to seed quality in organic production of grass and clover seed and how to improve yield

Summary

In conventional seed production of grasses and clover it is recognised that a low plant density in the seed crop stimulates the reproductive development and hence increase seed yield. Most temperate forage species of grasses and white clover establish slowly and have a relatively poor ground cover, which limits the competition against weeds. In order to optimise quality and yield in organic grass and clover seed production alternative establishment methods have been identified. These methods enhance crop competitiveness against weeds and allow for mechanical weed control.
Establishing the under sown seed crop right between the cereal cover crop row provides a higher ground cover, and the establishment rate of the seed crop is enhanced. This method of establishment is recommended when weed density is low or where the prevailing weeds produce seeds that can be separated from the harvested grass or clover seed. Establishing the under sown seed crop in the cereal row allows for different strategies of mechanical weed control and our results show that perennial ryegrass tolerates a range of strategies of mechanical weed control including up to three harrowings. However, grass and clover species with a low seed weight and/or a slow establishment rate might not establish successfully when sown in the cereal row.
Identifying the optimal establishment technique must take the occurrence of weed species and the weed density into account.