Effect of sowing depth on the germination and early seedling growth of Dialium guineense Willd
This study was carried out to determine the effect of different sowing depths on seed germination and seedling growth performance of Dialium guineense. The experiment was laid out in a Completely Randomized Design (CRD) with 5 treatments: 0, 3, 6, 9 and 12 cm sowing depths. Fifteen viable seeds were sown into 15 polypots filled with bulked forest topsoil for each treatment and this gave rise to a total of 75 seeds sown for the 5 treatments. Observation on germination was made and recorded daily for a period of 30 days after sowing (DAS). Inception of plumule emergence was observed and germination percentage calculated for each of the sowing depths (treatments). Evaluation of early seedling growth was based on height, collar diameter and leaf number. Observation on seedling growth performance commenced one month after sowing (MAS) and continued bi-weekly thereafter up to 12 weeks after sowing (WAS). Plumule emergence was earliest at 0 cm sowing depth (10 DAS) and latest at the 12 cm sowing depth (16 DAS). Germination percentage was highest (80.00%) at 3 and 6 cm sowing depths and lowest (13.33%) at 0 cm sowing depth. Highest mean seedling height and collar diameter were observed at 3cm sowing depth while the lowest mean seedling height was observed at 12 cm sowing depth at all growth stages (4, 6, 8, 10, and 12 WAS). Highest mean leaf number was observed in 3 and 6 cm sowing depths at 4 and 6 WAS and in 3 cm sowing at 8 to 12 WAS while lowest mean leaf number was observed in 12 cm sowing depth at 4 to 12 WAS. Mean seedling height did not vary significantly (p>0.05) among 3, 6 and 9 cm sowing depths at all stages of growth. Collar diameter did not vary significantly (p>0.05) among 3, 6 and 9 cm sowing depths at 4 WAS, among all the treatments, at 6 and 8 WAS, and among 6, 9 and 12 cm sowing depths at 10 and 12 WAS. Seedling growth generally decreased with increase in sowing depth. It is recommended that seeds of D. guineense should be sown at shallow depths (from 3 to 6 cm) since best germination and seedling growth were observed at the two depths.
Keywords: Dialium guineense, sowing depths, germination, early seedling growth