A manual of rice seed health testing - IRRI books - International Rice ...

solid pointed end. The tube and
sleeve have open slots in their walls.
When the slots are alined, seeds
drop into the cavity of the tube. To
close the slots, turn the tube. Tube
length and diameter depend on the
size of the container and kind of the
seed to be sampled.
The trier can be used horizontally
for vertically. A vertical trier should
be partitioned to assure even sampling
through the layers.
Insert the closed trier diagonally
into the bag or container. Alter insertion,
agitate it gently, and open and
close it several times to ensure filling.
Finally, close carefully before
drawing out the sample.
b) The Nobbe trier (Fig. 4.2a) is
suitable for sampling seed in bags
but not in bulk. It is constructed in
varying dimensions depending on
the kinds of seeds to be sampled.
The Nobbe trier is a pointed tube,
long enough to reach the center of
the bag, with an oval hole near the
pointed end, The instrument should
be approximately 500 mm long, including
the handle (about 100 mm
long) and point (about 60 mm), leaving
about 340 mm to penetrate the
bag. This should reach the center of
all types of bags. For cereals, the internal
diameter of the tube should be
about 14 mm. For clovers and similar
seeds, 10 mm is sufficient.
Insert the trier gently inlo the bag
(Fig. 4.2b), pointing upward at an
angle of about 30° to the horizontal,
with the hole facing downward, until
it reaches the center of the bag.
Rotate the trier 180°, bringing the
hole on top. Withdraw the trier with
decreasing speed so the quantity of
seed obtained from successive locations
increases progressively from
the center to the side of the bag. If,
howerver, the trier is long enough to
penetrate to the opposite side of the
bag, withdraw it at a relatively constant
speed. During withdrawal, the
trier should be gently agitated to
maintain an even flow of seed. The
more polished the inner surface of
the trier, the more freely the seed
will flow.
To sample the bottoms of standing
bags, raise them off the floor and
place them on top of other bags. The
holes that the trier made in the bags
may be closed by pushing the weave
back together.
c) Sampling by hand is difficult,
and should not be used for chaffy
seeds like rice.
3. Taking primary samples (Rule
2.6.4)
Primary samples of approxirnately
equal size shall be taken from each
container sampled. When the lot is
in containers (including bags), the
containers to be sampled shall be selected
at random throughout the lot
and primary samples drawn from
top, middle, or bottom portions of
the container but not necessarily
from more than one position in any
container. When the seed is in bulk
or in large containers, the primary
samples shall be drawn from random
positions or depths.
4. Obtaining the composite sample
(Rule 2.6.5)
If the primary samples appear uniform,
they shall be combined to form
the composite sample.
4.1 A sleeve-type
trier (grain probe).
4.2 a. Stick triers
(Nobbe trier).
b. Inserting a stick
trier in a sack of rice
to draw seeds.
20 Rice seed health testing manual