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For a sustainable woody crop industry the farming system will need to be optimized. This may be for
maximum mallee profitability, where mallee is the only crop, or maximum enterprise profitability for
combined wheat and mallee farming systems. This will require assessment of optimum block planting
arrangements for exclusive mallee systems, or intra and inter-row spacing for integrated mallee/wheat
systems. In both cases the economic return from the mallee crop and associated harvesting costs
needs to included.
Considerable capital has already been expended on establishing > 13 000 Ha of mallee in Western
Australia. Changing established mallee farming systems is unlikely, due to the capital invested in
establishing the crop and given that wheat production remains the main economic driver. Many
plantings have been in the ground for over a decade and will need to be harvested to reduce
competition with existing cereal crops. This will require alternative harvesting systems (e.g. feller
buncher), which is unlikely to be economical. Thereafter a more frequent harvesting schedule can
commence using the chipper harvester. This will depend on a market that can afford to cover harvest
and transport costs and required margins.
Appropriate layout of block plantings will need to be determined to maximize plant growth and
minimize harvest and transport costs. It is likely that mallee biomass supply to a processor will
comprise block plantings close to the processor, supplemented by existing feedstock from dispersed
alley plantings integrated in wheat farming systems. Block cultivation may comprise closely spaced
belts (10-30m) on marginal land close to the processor. Spacing will be determined by soil moisture
competition and yield. Harvest and transport logistics should be considered in determining layouts.
Harvesting efficiency will be improved when the concentration of biomass per metre of row is
maximised and distance between rows is minimised.
Where mallee planting is not intended for biomass removal, consideration needs to be given to
protocols for carbon credits. Existing guidelines indicate 2 row mallee planting is not eligible for
carbon credits. Approval should be sought for existing 2 row mallee layouts to be eligible for carbon
credits. Future plantings will need to take account of carbon accounting protocols.
High accuracy GPS autosteer systems are now becoming common place on the modern farm. As
mallees are a permanent feature in the landscape, any issues with compaction due to transport will be
a compounding problem. As the harvest and haul equipment will have considerable mass, confining
the wheeltracks to the same location will limit compaction. The ease of planting in straight line
versus on the contour should be considered. GPS guidance of both the planting and harvest
equipment (harvester + haulout) could prove beneficial.
Current knowledge on the importance of mallee plant structure and the influence on harvesting ability
and economics (age and size of tree, number and size of stems, species differences and opportunities
for genetic improvements) are based on the current alley system. This needs to be investigated for
the block planting scenario. Optimum harvest age will change with conditions and market
requirement which influences harvester performance.
Mallee planting, even in their current form, provides vegetative biodiversity in a wheat monoculture.
The collateral benefits of this biodiversity and the associated environmental dividend needs to be
quantified.
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