Biochar as a Nursery Media Amendment: Advancing Quality Seedling Production in Tropical and Temperate Tree Species

Biochar, a carbon-dense material produced through the thermochemical conversion of biomass in low-oxygen environments, is increasingly recognized as a durable component for nursery growing media. Traditional media, frequently demonstrate inadequate structural stability, diminished water retention, nutrient depletion, and reduced microbial activity, resulting in suboptimal seedling performance in forest nurseries. This systematic review of biochar consolidates published research assessing the impact of biochar incorporation in nursery growing media on the production of high-quality tree seedlings. Relevant literature from 2010 to 2026 for tropical and temperate tree species were analysed, emphasizing variations in biochar feedstock, pyrolysis parameters, and application rates in nursery seedlings. The analysed growth and quality parameters encompassed seedling height, collar diameter, biomass accumulation, root development, survival percentage, Dickson Quality Index, and Seedling Vigour Index. Tropical species like Acacia mangium, Afzelia Africana, Pterocarpus erinaceus, Eucalyptus grandis, Melia azedarach, and Faidherbia albida demonstrated notable advancements in biomass accumulation and root structure, whereas temperate species such as Pinus sylvestris and Quercus castaneifolia displayed improved growth and drought resilience. The application of biochar also augmented resistance to soil-borne pathogens, including Phytophthora spp., and improved physiological stability. Synergistic effects were often observed when biochar was integrated with fertilizers, organic amendments, or beneficial microorganisms, leading to enhanced nutrient availability, water retention, and microbial activity. Responses, however, differed based on feedstock type, pyrolysis temperature, and application rate. Biochar-enriched nursery media constitutes a promising approach for producing high-quality, resilient tree seedlings to enhance sustainable forestry and reforestation initiatives. Overall, low to moderate biochar rates (3–10% v/v) consistently improve seedling quality across tropical and temperate species, making biochar a promising amendment for climate‑resilient forestry.