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ate than a 170 tonne/ha crop of standing cane. The differences in productivity between green and
burnt cane are well documented.
Burnt crops are accepted as the easiest crops to harvest. Even older machines are able to achieve
ground speeds equating to high pour rates, providing the cane is not excessively lodged.
Up to crop sizes of 80 tonne/ha there is usually little difference in the expected pour rates for modern
harvesters between burnt and unburnt crops because pour rate is limited by maximum ground speed.
As crop size increases, the difference in productivity between the two harvesting modes increases.
Initially, the reduction in productivity is because of restrictions on cleaning system performance
(product quality issues). Visibility, difficulty in assessing position on the row and basecutter height
control issues also impact on the speed at which the operator is comfortable. As the crop size
continues to increase, maintaining effective feed becomes the major issue, resulting in stool damage
and increased levels of damaged billets in the cane supply.
Australian data indicates that typical daily productivity in an unburnt crop of 180-190 tonne/ha is 40%
of that in burnt cane and about 85% in 130 tonne/ha crops (Davis et al. 2000).
For whole-of-crop harvesting because there is no, or limited, cleaning being undertaken on the
machine, the delivery rate becomes limited primarily by machine volumetric capacity. The evenness
of feed (which dramatically impacts on cleaning system performance) becomes much less significant
as crop size increases.
160
140
120
Typical Maximum Pour Rate, t/hr
100
80
60
40
20
Burnt
Cane
0
0 50 100 150 200 250
Crop Size T/ha
Figure 2.7 Effect of crop size on maximum harvester (tracked machines) delivery rate in burnt and
green cane
In small crops, delivery rate is typically limited by maximum forward speed, however as crop size
increases, a range of other factors control the typical maximum delivery rates.
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