Effects of Soil Substrate on Germination and Seedling Growth of <i>Adansonia digitata L.</i> in Northwest Ethiopia

Adansonia digitata L. is a multipurpose dry forest tree species with potential contributions for food and nutrition security as well as ecological resilience. It is locally used for food, medicine, fiber, crafts, and income sources. However, the species exhibits poor natural regeneration and a declining population in the Northwest lowlands of Ethiopia. Hence, there is an urgent need for conservation and domestication of the species. However, there is limited documented knowledge on the nursery management of the species. Thus, this study aimed to determine the appropriate soil substrate for enhanced germination and seedling growth of Adansonia digitata. Complete randomized designs (CRD) with four soil substrate treatments in three replications were employed. The four soil substrates tested include local soil as a control (S1), 2:1:1 ratio of local soil, decomposed manure, and sand (S2), 3:1:1 local soil, decomposed manure, and sand (S3), and 3:2:1 local soil, decomposed manure, and sand (S4). For each treatment 48 plastic polythene pots filled with the specified substrate were used, and seeds treated with nicking were sown. Significant variations were observed in Adansonia digitata germination percentage and duration across soil substrates (P = 0.001 and P = 0.01) respectively. Among seedling growth performance parameters, significant variation was observed in root collar diameter (P = 0.046) among the soil substrates tested. In terms of seedling quality indicators computed, seedling vigour index was statistically significant across the soil substrates (P = 0.001). The highest germination (83.33 ± 2.27%), seedling root collar diameter (5.65 ± 0.9 cm), and vigour index (3150.0 ± 68) were recorded in treatment S3 (3:1:1 ratio of local soil, decomposed manure and sand). Additionally, S3 yields the better total dry biomass increment (71.53 ± 24%), quality index (0.63 ± 0.45), and total seedling dry weight (2.64 ± 1.5 g). However, the lowest germination, seedling morphological traits, biomass, and quality parameters were obtained in the control (S1) group. Based on the observed germination and seedling growth performance parameters, the present study recommended treatment S3 (3:1:1 ratio of local soil, decomposed manure and sand) for better seedling production of Adansonia digitata. Overall, this study highlighted the possibility of quality seedling production for the conservation and domestication of this key tree species.