Résumé
In Brazil, most Eucalyptus plantations are located in regions experiencing periods of water shortage where fertilizers such as potassium (K) are intensively used to achieve high productivity. Recently, sodium (Na) has also been considered a potential nutrient. As well as tree growth, wood properties are also an important factor to consider in order to measure the impacts of silvicultural practices and water deficit on forest productivity, since they are determinants for quality and yield of pulp and paper.In a split-plot experimental design with four and six-year-old Eucalyptus grandis trees, located in Su00e3o Paulo State, Brazil, we evaluate the effects of K and Na supply compared with a control treatment, under two water supply regimes (37% throughfall reduction versus no throughfall reduction) on stem volume, heartwood proportion, basic density, fiber, and vessel properties.Effects of Na fertilization on wood properties were more pronounced that K fertilization. Na detrimentally affected sapwood:heartwood ratio and wood basic density. However, both the K and Na supply increased stem volume by three and two-fold respectively. The beneficial effects of K and Na on stem volume, even under a water availability reduction, largely compensate for the loss in wood quality for pulp and paper production. Vessels features were responsive to fertilization. These findings predict that under water deficit, wood density and fiber features will not decline in commercial Eucalyptus grandis plantations fertilized with potassium. The use of sodium, as a substitute for potassium, should consider their negative impacts on wood density.