Alterações nas características químicas da madeira com a substituição do K por Na em plantações de eucalipto

Abstract

With the purpose of partial substitution of potassium by sodium in the forest plantations fertilization, the effect of the isolated performance of these nutrients on the chemical properties of young wood in Eucalyptus grandis trees was evaluated. Trees were planted at a 2mx3m spacing and 116 kg.ha -1 of K and 68.5 kg.ha -1 of Na were applied to them. Eucalypt trees were cut down from the 1st to the 4th year after planting in each fertilization treatment, being sectioned disks of wood in different positions of the trunk and marked the annual growth rings, estimated by a stem profile model. Representative samples of each annual ring, longitudinal position and treatment were obtained for determining the lignin, holocellulose and extractives. Eucalyptus trees that received application of potassium and sodium did not change significantly in chemical properties, indicating that the substitution of K by Na in fertilization of Eucalyptus plantations can be adopted without the alteration of the chemical properties in the young wood in the young trees. Annual evaluations indicated a significant reduction in average content of lignin and total extractives and an increase in average contents of holocellulose with increasing age of the trees. Consistent changes in the levels of chemical properties of wood for the longitudinal and ring growth were observed.