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Almost 80% of the industry now cuts green. There has also been significant move towards minimum
tillage and controlled traffic to reduce compaction caused by traffic associated with harvester and
haulout machinery. A major problem with compaction in the sugarcane cropping system has been due
to mismatched row and wheel spacings. Traditionally the sugarcane crop has been grown on 1.5 m
rows whereas harvesting and haulout equipment has a standard 1.85 m wheel spacing resulting in
encroachment on cropped areas causing compaction (see Section 2.2.1).
A key part of the farming system has been growing rotation crops such as legumes which is harvested
or left unharvested. Residue is then mulched into the soil or sugarcane planted into the residue. This
cropping system provides better-balanced biology and control of root pathogens, helps biologically
fix nitrogen, reduces the need for fertilizer nitrogen and improves soil organic matter and cane yield.
Sugar cane systems all rely on GPS guidance for precision planting and subsequent land management
and harvesting. The planting machine leaves the field in a furrowed condition, the sett being in the
bottom of the furrows covered by 50 to 100 mm of soil. Subsequent cultivation is designed to destroy
young weeds and grass growth and gradually fill in the furrow as the cane stools develop so that by
harvest time a flat surface or slight ridge along the length of the cane row facilitates harvesting.
Block sizes are driven by field width and also equipment considerations such as boomspray and
planting rigs, but also irrigation logistics
1.2 Crop Components and Uses
1.2.1 Crop Components
Mallee System
The conceptual biomass harvest and supply chain is based on principles described by Giles and
Harris (2003) and the current development of a prototype harvester by the Future Farm Industries
CRC and Biosystems Engineering is turning the concept into reality. The harvester is self-propelled,
straddles a single row when operating and moves continuously along the row. All above ground
biomass is collected and chipped by the harvester and delivered continuously into tractor drawn
haulout bins and the haulouts transport the chipped biomass out of the paddock to a roadside landing.
A short-term surge buffer at the landing, between the infield operations and the road transport stage,
will not permit any sorting of the material, so the delivered product at the processing facility will be
the green mixed whole-tree biomass.
The chipped biomass in its unsorted state is a mixture of wood chip, leaf, and residues of assorted
fines, bark and small twigs. The mixed material in chipped form is liable to decompose significantly
over a period of about a week. It is preferable to sort the leaf and residues from the wood chip if the
biomass is to be stored for more than a few days because clean chip can be stockpiled relatively
easily in its ex-harvester form, whereas the foliage and finer materials must be dried prior to longterm
storage. Decomposition of finer material will degrade the product, fungal spores from the
decomposing material represent an OSH issue, and spontaneous combustion of stacks is also a
significant risk.
The proportions of wood, leaf and residues is about one third each but these values vary widely
according to tree species and age at harvest. Biomass composition is more complex than for sugar
cane as mallees may be harvested over a wide range of ages, or over a wide range of mallee sizes.
Size (above ground biomass per mallee) is likely to be more important for harvest scheduling than
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