A greenhouse experiment was carried out to evaluate the genetic variability in the efficiency of phosphorus utilization in 18 half-sib families of Eucalyptus grandis W. Hill ex Maiden, submitted to three phosphorus levels (0, 200 and 400 mg/dm³ P2O5). The experiment was arranged in a completely randomized design, following an 18 x 3 factorial scheme totaling 54 treatments and three replications of two plants per pot, containing 7 dm³ of soil grown until 120 days after transplant. Height, collar diameter; and dry matter of roots, stems, branches, leaves, shoots and total dry matter, shoot-root rate and P concentration, content and utilization efficiency in the leaves and in the stems were evaluated. The families responded positively to fertilization, differently for each characteristic, with a tendency to stabilize at the highest level. The highest P absorption was observed when 400 mg/dm³ P2O5 were added. However, this was not accompanied by increased dry matter production, resulting in lower P utilization efficiency under this condition. In general, the genetic material evaluated presented low genetic variability, but it was possible to identify promising materials for the characteristics evaluated.
Forest improvement; forest nutrition; nutritional efficiency
