Agriculture Reference
In-Depth Information
Selection of Probes (or Triers)
Figure 3.3 shows the kinds of sampling probes (or triers) that are in common use in the seed industry.
Assuming that the lot to be sampled is completely homogenous, the sample could theoretically be taken
with any trier and still be representative of the parent seed lot, regardless of whether it is in bulk, in bags, or
other kind of containers. In practice, however, most seed on the market will be in cloth or paper bags that are
stacked, e.g., in 20-bag units on pallets in storage or marketing areas waiting to be sold or transported. The
probe used should be as small in diameter as possible, but large enough to allow the seed to low into the
slots along its length. Furthermore, the slots should be large enough to allow the seed to fall into the probe
without both ends of a seed “bridging” the slot from side to side at the same time. All probes used should be
long enough to reach across the entire width or length of the seed container. This increases the probability
that a truly representative sample will be obtained.
Figure 3.3 Left: different types of probes used for sampling seed. Not all types of probes are allowed for
oficial or accredited testing. Right: proper technique for sampling from a bag of seed (from Copeland and
McDonald, 2001).
Sampling Technique for Manually Inserted Probes
Regardless of which sampling instrument is used, the procedure by which the sample is drawn from an indi-
vidual bag or container should be carefully standardized. This helps ensure that any existing contamination
will have a chance of being represented in the sample. This will be enhanced by a carefully followed sam-
pling pattern. If shorter probes are used, both sides of the container should be sampled as far into the bag
as can be reached. If longer probes are used, they should be inserted diagonally through the bag to obtain
a complete cross section of the seed. The same number of probe entries are used per container and blended
into one composite sample. The probes should be inserted into bags at an angle (Fig. 3.3) from the top to
bottom of the bag, with the holes facing downward. The probe is rotated 180° so the holes face up, then
withdrawn slowly and evenly. This helps to ensure that heavier seed or inert matter components that tend
to work their way to the bottom of the bag or container will have a chance to be represented in the sample.
