Substrates for the production of Samanea saman (Jacq.) Merr seedlings inoculated with nitrogen-fixing bacteria and arbuscular mycorrhizal fungi

Samanea saman (Jacq.) Merr is a tree species widely used in forest restoration plantations and its symbiosis with nitrogen-fixing bacteria (NFB) and arbuscular mycorrhizal fungi (AMF) can promote seedling formation and establishment and growth in the field. The growth of S. saman seedlings inoculated with nitrogen-fixing bacteria and arbuscular mycorrhizal fungi grown on nine different substrates were evaluated in a greenhouse in this study. Seedling growth was promoted in substrates with lower bulk density and pH and higher total porosity, air-filled porosity and available Mg content. The nodulation of NFB was favored in the substrates with more available Mg, and AMF colonization and sporulation was favored in the substrates with a higher percentage of water buffering capacity. Seedlings produced on commercial substrates based on peat and pine bark showed superior growth. The peat-based “Carolina Soil™ electrical conductivity (EC) 0.7” favored nodulation, while the sewage sludge substrates and clayey subsoil mixture plus 10% poultry litter (V:V) promoted mycorrhizal colonization and sporulation.