EUCALYPTUS-GRANDIS FERTILIZER TRIALS - GROWTH, WOOD PROPERTIES AND KRAFT PULP YIELD

A fertilizer experiment was established with Eucalyptus grandis near G ympie, Queensland in 1987. Treatments included nitrogen (N) and phosph orus (P) fertilizer in factorial combination (five levels of each at r ates 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 do ubled from 76 m(3)/ha in unfertilized control plots to 145 m(3)/ha in the optimum treatment (N2P2). Trees from the five 'diagonal' treatment s of the factorial experiment (N0P0, N1P1, N2P2, N3P3, N4P4) were harv ested at 5 years of age for testing of wood and pulp properties. Compa red with values for unfertilized trees, basic density and pulp yield o f wood from trees in treatment N3P3 both increased by 5 to 6% (basic d ensity 412 kg/m(3) compared with 436 kg/m(3) and pulp yield of 47% com pared with 50%). The combined effect of these changes increased the qu antity 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 1 6 t/ha/a untreated to 32 t/ha/a for N3P3.