Abstract: Medicago sativa is an important forage in global cultivated grassland. Aiming to provide management guide for M. sativa grassland, we investigated the responses of seed germination and seedling growth to the variations of important environmental factors (temperature, light, and burial depth). We compared seed germination of M. sativa at five constant thermal treatments (10, 15, 20, 25, and 30 ℃) and five alternative temperatures (6/15, 10/20, 15/25, 15/30, and 20/30 ℃), accompanied with two light regimes, i.e. 12 h light/12 h dark and 24 h dark. Five sowing depths (1, 2, 3, 4, and 5 cm) were carried out to explore the effects of soil burial depth on seed emergence and seedling growth of M. sativa. Results showed that M. sativa could germinate to 50%-88% within a large temperature range. Light availability significantly promoted seed germination, especially at 10, 15, 30, 10/20 and 15/30 ℃. Seed germination ranged from 69% to 88% under light treatment and from 50% to 77% under dark treatment. There were no significant differences in seedling emergence percentage across different burial depths. Fresh and dry weight of shoot, root length and weight of the 1-2 cm burial depth treatments were all significantly higher than that of 3-5 cm burial depth treatments. In conclusion, M. stativa could germinate under broad ranges of constant or alternating temperatures of 6-30 ℃, indicating that there was no strict season requirement for sowing seeds. Light significantly promoted seed germination of M. stativa. The suitable burial depth was within 1-2 cm.

Key words: Medicago sativa, seed germination, cultivated grassland, burial depth, light.