Biochar as Phosphorus Conditioner in Substrate for Brazil Nut (Bertholletia excelsa Humb. & Bonpl.) Seedling Production in the Central Amazon

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