Allelopathic effects of root extracts from Medicago sativa on germination of three forage species

To provide a theoretical basis for exploring reasonable planting models, we used a bioassay to evaluate the allelopathic effects of a range of concentrations (0, 2.5, 5.0, 10.0, and 20.0 g·L⁻¹) of root extracts from alfalfa (Medicago sativa) on seed germination of three important forage species: Lolium perenne, L. multiflorum, and Phleum pratense The results showed that within the tested concentration range, root extracts from alfalfa had a significant inhibitory effect on the germination rate, germination vigor, germination index, and vigor index (response index, RI < 0). Furthermore, root extracts from alfalfa had a concentration effect on seedling height and root length of seedlings, that is, "low promotion and high inhibition." Some differences were observed in the responses to alfalfa allelopathy among the three grasses. The synthetical allelopathic index of L. perenne and L. multiflorum was negative under the action of root extract, which showed clear inhibitory effects (synthetical allelopathicindex, SE < 0). In conclusion, P. pratense has a stronger adaptability and resistance to the allelopathic inhibitory effect of alfalfa root extracts compared with L. perenne and L. multiflorum. Thus, P. pratense is more suitable for mixed sowing with alfalfa than L. perenne and L. multiflorum．