Agriculture Reference
In-Depth Information
3
Sampling
and
Subsampling
No matter how carefully and accurately the analysis is performed, it can only show the quality of the
sample tested/submitted. Thus, it is imperative that the sample be properly drawn and faithfully represent
the quality of the seed lot from which it is taken. If taken with careless or biased procedures, all subsequent
analyses may be meaningless and not representative of the actual quality of the seed lot. Any compromise
or disregard of the principles of good sampling risks a bias in the results and does a disservice to both the
producer and the consumer.
Although preliminary or check samples (mill checks) may be drawn at any time before or during seed
conditioning, the inal, or “oficial” sample should be taken after conditioning is completed so it will repre-
sent the seed as it is to be offered for sale. Depending on the kind of seed and the circumstances, the sample
may be taken with a specially designed sampling instrument (e.g., a probe or trier), by hand (the grab
method), or it may be drawn automatically at speciied intervals by a
mechanical sampler
. All techniques
will give a representative sample if properly drawn from homogenous seed lots.
Because of the variety of ways in which seed is stored and offered for sale, it may be found in various
types of containers, from small vegetable and lower seed packets, boxes and cans of grass seed, to large
bulk lots of cereal grain or soybean seed. Regardless of the container, the seed lot must be properly sampled
to represent the entire seed lot.
Rules and procedures for sampling under various conditions have been established by the Association
of Oficial Seed Analysts (AOSA) and the International Seed Testing Association (ISTA). These rules pro-
vide for sampling by use of standard sampling probes or triers, by mechanical samplers, by hand, or by
taking the entire container for testing purposes.
Sampling is usually performed in two steps. First, the sample to be submitted for analysis is drawn
from the bulk seed lot and sent to the laboratory. This is known as the
submitted sample
. Second, when it
reaches the laboratory, it must be further divided to a size that can be conveniently analyzed. This latter
sample is used for the actual analysis and is called the
working sample
. This sampling and subsampling
process is illustrated in Figure 3.1.
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