Despite the improved fertility from agricultural systems, some blue gum plantations grown on previous farmland in southern WA can respond strongly to fertilization with nitrogen (N) and phosphorus (P). On some sites it is possible to double the volume production of the plantations through judicious fertiliser application. In contrast, there are also many sites that do not respond to fertiliser. The absences of response to fertiliser are mostly due to either adequate nutrient levels, limited water supply on some sites or both. Both water availability and nutrient status need to be assessed in the development of a fertiliser program. While further refinement is required, we have synthesised the currently available data and developed a number of best-bet guidelines to help target fertiliser application to those plantations that are likely to respond to fertiliser application the most, and to provide recommendations on the types and rates of fertiliser required to optimize growth.
Nutrient pools and dynamics vary markedly with the management strategy for post-harvest slash. Slash contains relatively high quantities of nutrients that will be a serious drain on the site resources if they are removed. Estimates of direct fertiliser costs of up to $1000/ha would be required to replace just the macronutrients, N, P, K, Ca and Mg. The indirect costs of slash removal, including retention of soil on steep slopes and maintenance of soil organic matter can also be high, and are not accounted for in this calculation.
A range of projects have been conducted to help industry to better understand the nutrient management of plantations in southern Australia, and a range of tools have been released to help manage plantation nutrition, including FPOS, and Pro-Fert. A synthesis of these tools is presented, and discussed. Different tools take different approaches, but there is clearly still a gap in knowledge of the responses and diagnostics of response that is needed to be filled before a suitable tool can be developed that can be readily adopted by managers. This report provides the best and most current set of guidelines for managing nutrition in E. globulus. There is scope to markedly improve on this with a targeted project that combines both experimental and modelling approaches to produce the empirical information that can inform tools that can be deployed to managers.
Project number: VNC422-1617
