Nutrient accumulation and nutritional efficiency in eucalyptus

Eucalyptus accumulates large amounts of nutrients in its biomass and, in order to maintain high productivities, high doses of fertilizers are applied, mainly potassium. Adequate fertilization management requires information on nutrient contents in the various plant organs. This study aimed to use the boundary-line (BL) method to determine curves of nutrient accumulation in eucalyptus shoots. For this, a database containing information on yield and nutrient contents in the various plant organs was used. Scatter plots relating nutrient content in the areal part to trunk volume were constructed. In these graphs, points of the upper and lower edges of the cloud of points were selected, BLs were established and equations to quantify nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) accumulation were obtained. Subsequently, the K content obtained in boundary plants was correlated with those of the other nutrients in the same plants. The relationship between nutrient content and trunk volume allowed establishing the maximum and minimum accumulations for the same volume produced. Plants with highest K accumulation had 4.6, 2.07 and 2.0 less accumulation of N, P and Mg, respectively, than those with lowest K accumulation, for the same trunk volume. At the end, it is concluded that plants with higher K accumulation showed reduction in the absorption of N, P and Mg and lower efficiency in the use of K, P, Ca and Mg.