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Store Mustard Crop
With Care
By Bill Greuel, Provincial Specialist - Oilseeds
and Transgenic Crops, Saskatchewan Agriculture, Food and Rural
Revitalization
With harvest hopefully nearing completion throughout
most of the province, we need to turn our attention to other aspects
of the farming business. Marketing and contract obligations are
two that preoccupy many minds as we head into winter. However
if you don't pay attention to stored grain, marketing won't
be your concern.
Many factors, including seed maturity, conditioning,
seed moisture, temperature, storage length, mould growth, insects
and mites, dockage as well as storage and handling methods can
affect the quality of stored mustard seed. You need to address
and regularly monitor these factors in order to guarantee the
quality of stored seed.
For marketing purposes, mustard is dry at 10
per cent moisture. However that moisture level may not be safe
for long term storage. The oil fraction of mustard, which ranges
between 30 and 45 per cent depending on type, absorbs far less
moisture than the fibre and starch fractions of cereal grains.
The moisture in mustard is concentrated in a portion of the seed,
whereas in cereal grains the moisture is more evenly distributed.
For safe storage beyond five months, the moisture level at the
time of binning should be 8 per cent or lower.
Eight percent moisture
at harvest may seem low, but moisture level at harvest is not
static. Seed is a living organism and will continue to respire
for at least six weeks. Respiration produces both heat and moisture
and will increase moisture content by at least 1 per cent. If
moisture levels are high enough, mould growth will further increase
temperature and moisture as moulds are living, respiring organisms
as well.
I have touched upon some of the most important
factors that will affect stored mustard, namely moisture content
and temperature. Seed maturity, insects, mites and dockage are
also important factors to consider. Immature seed will have a
higher moisture content and higher green seed. Although green
seed does not contribute to the moisture level of the seed, it
will not clear out in the bin and is an important quality factor
we should not ignore. Few insects and mites feed on stored mustard,
but moisture level of the seed directly impacts their ability
to thrive in stored grain. In addition, their active growth and
respiration can further increase the temperature and moisture
level of stored grain. Dockage is usually three to four per cent
higher in moisture content than seed and can create pockets of
high moisture and temperature and provide a substrate for mould
growth.
Aeration of stored mustard can help condition
seed for safe storage, but has two distinct purposes: to produce
the lowest practical temperature of the seed and to minimize the
temperature variation within the bin. Forcing ambient air through
stored mustard seed via an aeration system will not drop the moisture
content of the seed. If the moisture content is above 11 per cent,
aeration is not sufficient to condition the seed for long term
storage. Because of the size and shape of mustard seeds, they
require significantly more air pressure for effective conditioning
than cereals. Consequently, systems designed for cereals may not
sufficiently cool mustard seed enough for safe storage.
Several factors can and will affect the quality
of stored grain but careful attention during harvest and in the
first few weeks of storage will mitigate many of these. However,
you have no better insurance against heated mustard than frequent
monitoring. If caught early enough, you can stop the heating process
by moving the grain to a new bin, cooling with aeration or simply
by removing a truckload of seed from the bottom and replacing
it back on top. Left unchecked, mustard that is heating can go
from number one to sample in a very short time.
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