Climate changes result in hydrological cycle alterations, with impacts on distribution and quantity of rainfall affecting forest plantations in the tropics and subtropics. Trees minimize water stress effects by leaf osmotic adjustments which are dependent on K ions. Eucalyptus plantations were established in tropical and subtropical soils especially poor in K. Fertilization by substitution of K by Na is a potential alternative way, at lower cost and greater availability, that is especially suitable for smallholder plantations. For these reasons, we studied respective K and Na fertilization effects on growth and basic wood density of Eucalyptus grandis plantations with different objectives (domestic energy, timber). Significant differences in volume of trunk and wood density were observed on 8-year-old E. grandis trees fertilized with Na vs. K and the control. Trees with Na fertilization showed a significantly higher volume with Na vs. the control and a lower volume vs. K. Wood density and radial variability were significantly lower compared to trees with K and the control. In this paper we discuss the advantages of Na fertilization both to minimize the drought stress effect due to global climate change and to optimize economically the wood production of smallholder plantations. (Texte intégral)