Biochar-based seed coating dramatically increases seedling germination and field establishment of arctic lupine (Lupinus arcticus)

Abstract: Positive effects of biochar on early plant performance suggest the potential use of biochar-based seed coatings in the context of restoration and reforestation programs. We present results of field and lab trials examining effects of biochar-based seed coatings on 8 common boreal shrub and tree species. The application of biochar coatings (using polyvinyl acetate as a binding agent) inhibited germination for 7 species (3 conifers and 4 shrubs species) but greatly enhanced seedling establishment of arctic lupine (Lupinus arcticus S. Watson), with a ~13-fold increase relative to controls. Both lab and field provided similar results. In the field trial we observed that presence of natural charcoal and mineral soil approximately doubled the chances of lupine establishment. The findings suggest that both biochars and natural fire residues act as a germination trigger for arctic lupine seeds, and also indicate the importance of species-specific effects in using biochar-based seed coating for artificial seed enhancement. To enhance the effectiveness of biochar-based reforestation strategies on direct seeding, future studies should focus on potential germination stimulants and identifying binding agents suitable for a broad range of species.