| Germination rate and germination vigor of different Cosmos sulphureus varieties were studied under laboratory conditions,
and the effect of seeding time (April to August) and cover thickness (0.3, 0.8, 1.6, 2.4 and 3.0 cm) on the emergence rate, seedling height and seedling mortality were also studied in experimental field. The results showed that the germination rate and germination vigor with different varieties of Cosmos sulphureus had a large difference, the germination rate and germination vigor of Yellow variety were 88.33% and 81.67% respectively, the germination rate and germination vigor of Orange variety were 80.67% and 68.67% respectively, the germination rate and germination vigor of Red variety were 66.67% and 47.33% respectively. When the cover thickness was greater than 0.3 cm, the emergence rate decreased obviously as the cover thickness added. When the cover thickness was greater than 0.8 cm, the seedling mortality increased significantly as the cover thickness added. When the cover thickness was lower than 2.4 cm, the difference of seedling height wasn’t obvious, and when the cover thickness was 3.0 cm, no seedlings emerged. The seedling mortality was the highest at August, and a few of seedlings were dead at July, no seedlings dead from April to June. In a word, the less sowing seed quantity of per unit of Cosmos sulphureus was the Yellow variety, the appropriate seeding time was April to June and the appropriate cover thickness was 0.3 cm to 0.8 cm. |
