best practice management guide for south-eastern Australia - Grains ...

Post-harvest management
15. Post-harvest management
Paul Parker, NSW DPI
Retaining crop residues is central to most modern farming
systems in south-east Australia. Retained stubble has many
benefits, with soil moisture conservation a top priority in
Australia’s highly variable climate. Canola harvest residue
spread across the header harvesting width will maximise the
amount of soil moisture conserved and may help protect
the soil against wind and water erosion. In some instances
stubble removal, partial removal or burning may be necessary
to reduce disease levels and weed seed numbers or to
overcome difficulties with establishing the following crop.
Feed quality of
canola stubble
Canola stubble has little grazing value due to its poor feed
quality. Tests of stubble show that metabolisable energy
and crude protein are well below the minimum survival
requirements for livestock. However, volunteer canola
germinating after harvest can provide worthwhile summer or
autumn feed.
Disease management
Burning canola stubble will typically remove about half of the
available stubble. As blackleg spores originate from canola
stubble, burning will reduce blackleg severity but generally
there will still be enough spores to initiate the annual disease
cycle. After the severe bushfires on the Eyre Peninsula of
South Australia in 2005, which burnt all canola stubble,
canola crops in the following year still suffered yield losses
from blackleg in susceptible varieties (see chapter 10).
Research has also shown that a good hot burn can
be effective in destroying many of the sclerotes (fungal
fruiting bodies) of the disease sclerotinia. However, it will
not eliminate the problem as most burns will not destroy
all sclerotes and sclerotinia spores are airborne, meaning
they can travel a considerable distance from neighbouring
paddocks.
Canola stubble does not burn as readily or completely
as cereals; usually the standing stubble between the
header trash windrows remains unburnt and is left to stand
if a cereal crop is to follow. This standing material rarely
presents a problem at sowing or for the germination and
establishment of cereals. If there are no disease or weed
seed issues harvest residue should be spread across the
harvest width.
Figure 15.1 Storability of canola as a function of
temperature, moisture content and oil content
Moisture content at 60% rh
8.0
7.5
7.0
6.5
6.0
Safe
Potentially unsafe
5.5
35 40 45 50 55
Oil content (% dry matter basis)
35ºC 25ºC 15ºC 5ºC
SOURCE: R. Steele
Grain storage and
drying
Don McCaffery, NSW DPI and Neil Barker,
GraincCorp
Grain storage
Most harvested canola is not stored on-farm in south-east
Australia but is transported direct from the paddock to a
major grain bulk handler or centralised storage. However, a
small proportion is stored on-farm for a short time (two to
four months) for logistical reasons such as delayed delivery
arrangements with crushers.
Canola is much more difficult to store than cereals. It
requires a lower storage temperature and must be aerated
to preserve its quality and prevent insect infestations.
To maintain its market value canola must:
n have a high oil content of good colour;
n be low in free fatty acids;
n contain no residues of unregistered chemicals or residues
above permitted limits;
n be relatively low in moisture and temperature; and
n be free of stored product insect pests, moulds and
mycotoxins.
The storage conditions and processes affect many quality
parameters. The most appropriate storage conditions are
to maintain temperature of the seed below 20°C and seed
moisture below seven per cent. Figure 15.1 is the best guide
to determine if a load of canola of known moisture content
and oil content is safely storable under Australian conditions.
It shows the relationship between moisture content, oil
Canola best practice management guide
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