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1. Crop Production
This section looks at the reasons that there is a mallee resource in Australia and investigates the
various crop production systems that are currently being utilised, predominantly in Western
Australia, and compares them to the sugar cane crop production system—a similar system producing
a high volume, low-value, low density product. Crop production systems play a critical role when
considering improvements to supply chain management.
1.1 Cropping System
1.1.1 Historical Perspective
Mallee System
In Australia, the extensive arable agriculture land comprises of, on average, a 250 km wide belt
between the high rainfall forested eastern, southern and south-western coastal regions and the arid
interior of the continent. This region lies between the 300 and 600 mm mean annual rainfall isohyets
(see Figure 1.1) and contains the bulk of the nation’s ~60 million ha of arable land. This land was
originally vegetated with native eucalypt woodland/shrubland, and is now known as the ‘wheatbelt’
or ‘wheat/sheep zone’.
The wheat belt consists generally of old, geologically stable regions of low relief with winter
dominant rainfall and an excess of evaporation over rainfall with the rainfall being captured by the
generally deep soils and discharged in summer through transpiration by the deep-rooted native
vegetation. This balance between rainfall and evapotranspiration meant that the small amount of salt
arriving by rainfall accumulated in the deep soil profiles with stream flow volumes low. The natural
ecosystems had; relatively dry subsoil profiles, a substantial amount of salt in stable storage in the
deep subsoils, groundwater systems that were not extensive, and stream flow that was intermittent but
relatively fresh.
The replacement of the perennial woody vegetation by winter-grown annual crops and pastures leads
to a small but significant reduction in plant water use forcing a very large change in the storage and
stream flow components of the water balance, such that the hydrological character of the whole
landscape is slowly but comprehensively changed (Bartle and Abadi, 2010). Groundwater systems
progressively expanded in thickness and area, to intercept and mobilise previously stable soil salt
stores. The hydraulic conductivity and slope of the saturated layer /aquifer is generally low causing
the water to move slowly downslope. The low relief means that when brackish or saline groundwater
eventually intersects the surface, it can discharge over extensive areas, degrading soils and streams.
By 2050, the forecast potential for damage to agricultural land, remnant vegetation and infrastructure
is considerable, totalling about 11 million hectares of agricultural land, 2 million ha of remnant
vegetation, 39,500 km of streams and lake perimeters, 3,600 km of railway, 55,400 km of roads and
over 200 towns in WA, South Australia, Victoria and NSW (Bartle et al, 2007).
As a result, integration of perennial plants back into this agricultural system has been undertaken to
halt the spread of these saline areas with the aim of preserving long-term sustainability. Because of
the scale of the problem observed in the WA wheat belt, it was always recognised that this
revegetation would need to very extensive, so it would also need to sustain itself economically, to be
a crop in its own right. Mallee eucalypts are one of the predominant groups of perennial species
utilised (principally in WA) to address this salinity issue (Bartle and Abadi, 2010). This has provided
farmers with an additional product stream (woody biomass feedstock) that provides the impetus
behind this investigation.
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