The objective of this work was to evaluate the effects of fertilization, spatial arrangement and age on the biomass production in eucalyptus. The experiment was set up in a randomized block design with four replicates. Overall, 15 fertilizations adopted by forest companies in plots were evaluated, and two arrangements, 3.0 x 3.0 m and 6.0 x 1.5 m, were tested in subplots. Diameter at 1.30 m and total height were measured at 12, 24, 36, 48 and 60 months after planting to estimate trunk biomass. Dependence between commercial fertilization and arrangement were observed for trunk biomass. The biomass production rate in treatments where higher amounts of nutrients were applied decreased from the second year. The 3.0 x 3.0 m arrangement proved to be the most attractive option at 60 months using treatment with 2000 kg of agrosilicon, 400 kg of reactive phosphate, 130 kg of 04:26:16 + 0.5% Cu + 0.5% Zn and 150 kg of KCl + 1% B.
