The objective of this study was to evaluate the interaction of biochar and residual phosphorus in substrate for seedling production in Brazil nut. A greenhouse experiment was carried out with the following treatments: five doses of bio-carbon (0, 20, 40, 60 and 80 t ha-1) and residual effect of two levels of phosphorus (0 and 100 kg ha-1 of P2O5) with 4 replicates. The height of the plants, stem diameter and number of leaves evaluated monthly were evaluated. At the end (180 days), the plants were removed from the pots and the dry matter of the seedlings, absolute growth rate, height / diameter and dry matter ratio of shoots / roots, number of leaves, leaf gain and quality index of seedlings. There was a significant interaction between the biochar and residual phosphorus interaction. The elevation of the bioburden doses did not influence any variables with residual phosphorus. In the absence of phosphorus, the doses of up to 40 t ha-1 of biochar promoted the highest values of the analyzed variables. Higher doses of biochar (> 40 t.ha-1) reduced the growth and quality of seedlings, however, it was found that under phosphate fertilization, the seedlings were obtained better growth results.

Keywords: Phosphate fertilization; Pyrogenic coal; Seedling quality; Brazil Nut.