Response of Eucalyptus nitens and Eucalyptus regnans seedlings to application of various fertilisers at planting or soon after planting.

A site which had previously carried a high quality Eucalyptus regnans F.Mueller forest, but which had marginal soil nutrient reserves, was selected to trial four fertiliser options for establishment of Eucalyptus nitens (Dean et Maiden) Maiden andii. regnans sawlog plantations. Apart from the fertiliser options, current operational plantation establishment practices were used. Application of a nitrogen-phosphorus fertiliser shortly after planting produced increased growth for E. nitens amounting to 30 m3/ha by age 7 years. Eucalyptus regnans also responded to fertiliser application, but overall growth was less than half that of the E. nitens. This slower growth was due to early severe and repeated insect attacks. Insect attack also caused increased double and multiple leadering in the E. regnans. Normal rates of nitrogen-phosphorus fertiliser application (25 g N and 11 g P/tree) resulted in an increase in branch size compared with trees without fertiliser, and the mean largest branch diameter was increased by 6 mm for E. nitens. Multiple leadering also increased, from 2 % to 10%. Very high rates of fertiliser addition over the first 6 months