Effect of substrate and seed size on the germination and seedling growth of Faidherbia albida (Delile) A. Chev. in Burkina Faso

Faidherbia albida (Delile) A. Chev is a socio-economically significant agroforestry species in arid and semi-arid regions of Africa. However, its natural populations have declined significantly, primarily due to poor seed regeneration and limited adoption by local communities, hindered by its physical dormancy and slow growth. This study investigated the influence of substrate type and seed size on the germination and early growth of F. albida . Therefore, seeds of F. albida were categorized into three size classes based on their diameter: large (≥ 4.5 mm), medium (4.0–4.49 mm), and small (< 4.0 mm). After pretreatment with concentrated sulfuric acid (98%; 5 min), the seeds were sown in pots (40 cm height, 12 cm diameter, one per pot) using a randomized complete block design. The experimental layout included two substrates (desert sand and topsoil) and five replicates, with 10 seeds per replicate. The results of Generalized Linear Models (quasibinomial/gaussian/quasipoisson) showed that germination varied significantly according to seed size ( p < 0.001), with large seeds achieving 96 ± 6.7% success compared to 32 ± 9.9% for small seeds. Critically, germination kinetics were strictly size-dependent ( p < 0.001); large seeds exhibited near-instantaneous emergence (1-day latency) and high vigor indices, while small seeds showed significant delays (4-day latency) and a protracted mean germination time. Although substrate type did not significantly affect final germination percentage ( p = 0.1097), it strongly influenced subsequent seedling development. Seedlings from large seeds grown on topsoil reached the highest collar diameter (0.23 ± 0.05 cm), height (22.29 ± 7.67 cm), and the number of ramifications (1.61 ± 2.15), whereas desert sand limited growth regardless of caliber. Optimized regeneration of F. albida thus relies on a synergy between seed size and substrate quality. Utilizing large seeds in topsoil provides the highest vigor and growth prospects, offering a strategic pathway for successful reforestation and sustainable agroforestry management of arid and semi-arid zone.