To analyse whether biochar from the rachis of the babassu palm, mixed with dystrophic yellow latosol in different proportions, has a beneficial effect on soybean production after 26 months of incubation. Does babassu rachis biochar have a residual effect? The residual effects of biochar produced from babassu palm rachis on soybean cultivation were investigated after three successive cycles of lettuce production. A completely randomized design was used, in a 4¿×¿2 factorial with seven replications. The treatments consisted of four doses of babassu biochar (0, 10, 20 and 30 t ha-1) combined with two levels of fertilization (with and without mineral fertilizer). Plant height and stem diameter were assessed for growth analysis; at the end of the cycle, root length, dry mass of the aerial, number of grains and dry mass of grains were also measured. The application of 30 t ha-1 of biochar combined with mineral fertilization, followed by the 20 t ha-1 dose without fertilization, provided the greatest increases in plant height and grain dry mass of soybean. Grain number was more closely associated with the application of 10 t ha-1 biochar combined with fertilization. The 20 t ha-1 dose of biochar, even in the absence of mineral fertilization, promoted significant increases in grain dry mass, demonstrating its residual effect. The combination of biochar and mineral fertilizer increased plant growth, grain number and dry matter production, demonstrating the effectiveness of this interaction for soybean production performance.