Competitive forbs in high-producing temporary grasslands with perennial ryegrass and red clover can increase plant diversity and herbage yield

In highly productive temporary grasslands in Europe, plant diversity is usually low. Some non-leguminous species have shown a high competitive ability in temporary grasslands and can increase plant diversity without compromising yields. In an experiment, the competitiveness and productivity of three forb species: chicory (Cichorium intybus), ribwort plantain (Plantago lanceolata) and caraway (Carum carvi), grown in different proportions in mixtures including traditional sown grassland species, perennial ryegrass and red clover, were examined with slurry application as an additional factor. Dry matter (DM) yield and botanical composition were measured during one complete growing season. Annual DM yields were mostly similar when forbs were included in the grassland mixture. A three-species mixture (perennial ryegrass, red clover and ribwort plantain) had the highest yield potential, especially for the slurry application treatment. Chicory and ribwort plantain were highly competitive in the mixtures. The response in the DM yield of perennial ryegrass to slurry application was considerable, but no consistent trend was found in the forbs. In conclusion, forbs contributed to increased plant species diversity and herbage DM yield, and fertilisation had positive effect on herbage yield of grassland mixtures