<em>Eucalyptus globulus</em> Mid-Rotation Fertiliser Trial

AIMS:
To determine the growth response of Eucalyptus globulus to fertiliser applied mid-rotation.

CONCLUSIONS:
1. E. globulus growth responses to mid-rotation fertiliser additions vary greatly from site to site depending on many factors such as original site fertility and water storage.
2. Aside from sites with poor initial soil fertility, growth and stand volume increases after the application of treatment rates in the present trial were minimal.
3. Although improved nutrition may aid productivity, the reliance on water availability cannot be understated and this is the primary limiting determinant to E. globulus productivity in the region.
4. A number of nutrient elements were consistently marginal across the three sites, but P levels found in foliage are considered critically low, in turn increasing the N:P ratio. This was alleviated to a small extent by mid-rotation fertiliser addition.

RECOMMENDATIONS:
• Unless sub-optimal tree growth on a site can be directly linked to nutrient status, broad scale mid-rotation application of fertiliser to E. globulus cannot be recommended.
• An eventual shift to site-specific fertilisation may be required, but further work will be required, in conjunction with soil and tree spacing studies, to determine site-specific prescriptions.
• The critically low P status of trees stemming from low-P soils in the region suggest a role for increasing the P content in fertiliser mixes in any future investigation.
• Similarly, micronutrient levels, especially Zn and Cu, may require increases to enable a better balance of nutrients for eucalypt growth. Future work on eucalypt fertilisers should address this as the present mixes developed for pines are not as applicable to eucalypt species.