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1.1.4 Growth Cycle
Mallee System
Mallees have an initial phase of growth which may be described as a sapling stage, leading to the first
harvest. From then on the crop can be repeatedly harvested as it regenerates readily from the
lignotuber, which is a modified underground stem. In old mallee stands in Victoria and NSW, mallees
have been harvested repeatedly on short cycles (typically one to two years) for many decades. In the
industry model promoted in WA, where harvest intervals will be much longer (up to ten years) there
will be some mortality but as there has not been any sustained harvesting of mallees in this system, it
is not known how long a stand of mallees will persist, or how effectively the survivors will
compensate for losses (by utilising the resources previously used by dead individuals) over several
decades. The issue or mortality is covered further in section 1.1.5 below.
The time between harvests varies mostly with available soil moisture and rainfall; growth on 19
widely dispersed trial sites in WA, measuring both unharvested mallee growth and growth of three
and four year old coppice has recently been published by Peck et al (2011). Applying the estimation
that harvesting efficiency demands at least 20 green tonnes of biomass per kilometre of row, the time
to first harvest and between subsequent coppice harvests will range from four to ten years. Some poor
sites may take longer and perhaps should be considered unsuitable for mallee cropping. Harvesting
may also need to take into account the land use adjacent to the mallees at harvest, and it may be
preferable to avoid harvesting the mallees at a time when high return annual crops in the adjacent
alleys are in the latter half of their growing season.
The complexity of harvest scheduling makes coordinated regional harvest planning essential to give
markets certainty of consistent supply. However the mallees will not deteriorate in quality if left
another season or two, provided the largest individual plants do not grow beyond the capacity of the
harvester.
Table 1.2 The changing harvest cycle length due to configuration and climatic conditions
Sugar system
The current sugar production system consists of the plant crop and three or more ratoons that are
driven by the incidents of disease and weeds. The crops in the warmer growing regions (all of Qld)
are harvested every year (weather permitting) with a greater proportion of standover crops
predominating in the cooler areas of Northern NSW. A legume crop or other small crops may be
grown in the fallow period between plough-out and replanting, or to break the monoculture.
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