To study nitrogen, phosphorous and potassium demand of eucalyptus forest fertilization experiments were carried out in three different climatic zones of the VIII Region of Chile. Data on nutrients accumulation were obtained for the first three years of growth. The higher nutrient accumulation was observed in the fertilized plots. The nutrients demand varied with time, which is explained by the difference in the biomass proportion of the aerial components (leaves, branches, wood and bark). Additionally, nutrient demand was linked to biomass partitioning and nutrient concentration on the different parts of the tree. Nutrient concentration of the leaves was the highest, making this tissue the major sink, even though their relative biomass decreased in relation to the total biomass as the trees aged. On the contrary, the wood always had the lowest nutrient concentration, but its relative biomass increased with time, which made the net demand (kg nutrient 100 kg biomass) decrease as trees aged.