Regulation of clover content by choice of ryegrass variety or by mixing varieties in short rotation leys

The legume content in short rotation mixed leys is generally larger in organic production than in conventional, because application of mineral nitrogen favours grasses in competition with legumes. A large proportion of white clover in the diet of ruminants may cause problems with bloat. The purpose of this study was to test the effect of grass varieties or combinations of varieties on clover percentage and ley yield. Different varieties of perennial ryegrass (Lolium perenne L.) and Festulolium (Festulolium braunii Richt.) were compared in mixed swards with white clover (Trifolium repens L.) in a field experiment in east-central (Uppsala) and south-west Sweden (Rådde). The clover DM proportion of total yield was usually more than 50% at Rådde, but generally less than 50% at Uppsala. At Uppsala, an increase in grass yield resulted in a corresponding decrease in clover yield. At Rådde, grass performance affected total yield, but not clover yield. It was concluded that the clover content in short-rotation leys can be restricted by using competitive and persistent varieties of grass, but it could not be shown that grass mixtures are more competitive than their constituent components