The distribution of the pejibaye's (Bactris gasipaes) root biomass and absorbtive area was studied in a clay textured, yellow Oxisol, near Manaus, Amazonas, Brazil. Approximately 80% of the biomass was found in the Ap horizon and 90% of this within the crown projection area. Total biomass was estimated at 72 kg, without, however, including the very large mass immediately below the stem. The root surface area increased significantly as distance from the stem increased, due to the increase in the proportion of third and fourth order roots, although its abundance per m3 diminished like that of the biomass. The total root surface area was estimated at 545 m2, of which 50% is probably active in nutrient absorbtion. The observed distribution suggested that there are absorbtive roots at least 8-9 m from the stem. Fertilizer placement should be within and just outside of the crown projection area.
Pejibaye; Bactris gasipaes; root system; biomass; root absorbtive area