The present work had the objective to evaluate the increment in diameter of Eucalyptus grandis trees for 24 months and its relationship with climatic variables and mineral fertilization. The trees were planted at spacing of 3x2 m and fertilized with potassium and sodium (planting, 6 and 12 months). Twenty eucalypt trees were selected by treatment according with the distribution of basal area of the plantation and dendrometer bands were fixed at DBH. The results showed a clear effect of climate seasonality on the increment of eucalypt trees, with periods of maximum and minimum growth and a delay period (lag) of 28 days, due to the response of cambial activity to climate variations. The application of potassium in relationship of sodium and control promoted greater rate of increment growth of eucalypt trees, with values of 4.14; 3.28 and 3.08 cm, respectively.