Predictive relationships to assist fertiliser use decision-making in eucalypt plantations
Many hardwood plantations in southern Australia are ready for harvesting and subsequent replanting. However, while previous experience shows that applying appropriate amounts of fertiliser can prevent second rotation trees being less productive than first rotation trees, there is no reliable, cost-effective method to predict how a plantation will respond to fertiliser or when is the best time to apply it.
The aim of this study was to synthesise the results of such datasets to: (i) describe the magnitude and duration of growth response to fertiliser applied at establishment (age 0+1), mid-rotation (age 4-5) and both establishment and mid-rotation (age 0, 1 and 4) and (ii) to develop a robust method of identifying sites more likely to respond to establishment and/or mid-rotation fertiliser application.
Researchers determined that fertilising a plantation at planting increases the plantation’s final volume (at year 10) by 5.6%, whereas fertilising the plantation mid-rotation increases volume by up to 20.8% at responsive sites. Those plantations that were fertilised at planting and at mid-rotation showed a 10.6% increase in volume relative to control sites.
The research also compared predictive models with actual wood volumes from plantation test sites. Although the best models only predicted short-term growth response (i.e. one year after fertiliser application) with any level of accuracy, without better models being available, they do have significant value, particularly in identifying sites highly unlikely to respond to fertiliser. The researchers suggest plantation managers use the models as tools to rank sites according to predicted fertiliser response.