Eucalyptus grandis fertilizer trials: growth, wood properties and kraft pulp yield

A fertilizer experiment was established with Eucalyptus grandis near Gympie, Queensland in 1987. Treatments included nitrogen (N) and phosphorus (P) fertilizer in factorial combination (five levels of each at rates of up to 1600 kg/ha N and 480 kg/ha P). Application of fertilizer substantially improved tree growth with optimum response at 800 kg/ha N and 60 kg/ha P (N3P1). Volume production at age 5.6 years almost doubled from 76 m(3)/ha in unfertilized control plots to 145 m(3)/ha in the optimum treatment (N2P2). Trees from the five 'diagonal' treatments of the factorial experiment (N0P0, N1P1, N2P2, N3P3, N4P4) were harvested at 5 years of age for testing of wood and pulp properties. Compared with values for unfertilized trees, basic density and pulp yield of wood from trees in treatment N3P3 both increased by 5 to 6% (basic density 412 kg/m(3) compared with 436 kg/m(3) and pulp yield of 47% compared with 50%). The combined effect of these changes increased the quantity of screened pulp per unit volume of wood (pulpwood productivity) by about 12% from 194 to 217 kilograms pulp per cubic metre of wood. Production of screened pulp on a plantation area basis doubled from 16 t/ha/a untreated to 32 t/ha/a for N3P3.