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To optimize seedling production for reforestation of degraded dryland with A. senegal seeds, a study was conducted on the effect of boiled water treatment, growing media, sowing depth on seed germination and seedling growth of A. senegal. Three different growing media (farm soil, forest soil and sand soil), boiled water seed pre-treatment for 5 and 10 minutes, untreated seeds as control and three sowing depths (2, 4 and 6 cm) were the treatments investigated. The experimental design was a nested (Split plot) design. It was observed that sowing depth significantly affected the germination percent of the seeds and seedling growth; seedling emergence time increased with sowing depth. The highest cumulative germination percentage (CGP) (100%) was obtained from untreated seeds sown in sand soil at 2 cm depth while the lowest germination percentage (8%) was obtained from seeds pre-treated for 5 min in boiled water and sown in sand soil at 6 cm depth. Untreated seeds sown at 2 cm depth in sand soil germinated completely on the seventh day after sowing while it took about 17 days in farm and forest soils but 18 days in sand soil to reach the maximum recorded CGP for the treatment. Seedling height and branch number were higher for seedlings grown on forest soil. It was concluded that among the depths considered 2 cm was the optimum sowing depth for the species in all the tested growing media. Likewise, sand soil was found to be the best growing medium for germination of untreated seeds sown at 2 cm depth. Moreover, seed pre-treatment for 5 min in boiled water could be recommended for A. senegal seeds if farm and forest soil should be used as growing media. Seedling growth was found to be the best in forest soil when seeds were sown at 2 cm depth.
Keywords: A. senegal, Sowing depth, Growing media, Seed treatment, germination, Seedling growth