Biochar from eucalyptus biomass and the quality of seedlings

Biochar shows important characteristics required for the substrate, acting as a conditioner and improving soil properties. This study aimed to evaluate the effects of adding different proportions of eucalyptus bark biochar to the substrate, produced at different pyrolysis temperatures, on the quality of Eucalyptus grandis seedlings. The treatments were distributed in a randomized block design in a 4 x 4 + 1 factorial scheme: four pyrolysis temperatures of the biochar (250, 350, 450, and 600 °C), four proportions of biochar (2.5, 5, 10, and 15% of the tube volume) and a control (no biochar), added to a substrate made up of 80% coconut fiber and 20% vermiculite. The substrate was chemically characterized and the seedlings were evaluated after 90 days in terms of neck diameter, height, aerial and root phytomass, Dickson quality index, and classified in terms of root system quality. The composition of the substrate provided optimum root development for the seedlings. In the treatments with higher pyrolysis temperatures and proportions of biochar, there was a reduction in the availability of phosphorus, and an increase in pH and Na levels, which are not recommended for the substrates in treatments T13, T16, and T17.