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Sampling for moisture determination

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The sub-sample for moisture determination must be done in ... Foil or polythene bags that can be heat-sealed. Glass or polythene bottles with an airtight top ... – PowerPoint PPT presentation

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Title: Sampling for moisture determination


1
Sampling for moisture determination
Dr. Leena Pietilä ISTA Bulking and Sampling
Committee
2
ISTA Rules and sampling for moisture determination
  • The sub-sample for moisture determination must
    be done in such a way that changes in moisture
    content are minimal (2.5.1.5)
  • Submitted samples must be dispatched to the seed
    laboratory without delay (2.5.1.6)

3
The Rules and sampling for moisture determination
  • The seed may not be exposed to the air during
    sample reduction for more than 30 seconds
    (2.5.2.2 9.1.5.2)
  • Take first the sub-sample for moisture
    determination from the composite sample
  • Mixing by stirring the sample with a spoon
  • OR Pour the sample back and forth between two
    containers (9.1.5.2). The openings of the
    containers need to be of similar size.

4
Taking a sub-sample for moisture determination
  • Take at minimum three spoonfuls (2.5.2.2
    9.1.5.2)
  • As much air as possible must be excluded from the
    container (2.5.1.6 9.1.5.1), e.g. the
    container must be filled to the brim

5
Examples of containers that are used for samples
for moisture determination
  • Re-sealable plastic bags
  • Foil or polythene bags that can be heat-sealed
  • Glass or polythene bottles with an airtight top
  • It may be worth of testing whether the container
    is moisture proof

6
Sample reduction
  • The ISTA Rules describe eight different sample
    reduction methods
  • The ISTA methods must be followed, if the aim is
    to issue an ISTA certificate

7
Sample reduction
  • If the composite sample is too big, it must be
    reduced to a size prescribed in the Rules
  • Before reduction, the composite sample need to be
    mixed
  • Chaffy species three times, non-chaffy species
    two times

8
Sample reduction
  • No mixing before reduction is needed, if rotary
    divider or variable sample divider are used
  • All the composite sample must be reduced

9
Instruments for sample reduction
  • sample dividers
  • by hand

10
Working quality of sample dividers
  • Working quality of sample dividers must be
    checked regularly
  • ISTA Handbook on Seed Sampling (Chapter 6.6)
    gives guidance
  • Also other methods are used e.g. comparison of
    the halved samples with ISTA tolerance tables
    (Tables 3.3, 4.1, 5.2)

11
Checking working quality of dividers (ISTA
Handbook on Seed Sampling)
  • Prepare a standard sample by mixing two kind of
    seeds
  • E.g. 20 of small seeded species, 80
    large-seeded species
  • Reduce the sample to 1/8
  • Take one of the 1/8, separate the different seeds
    by a sieve and weigh the fraction
  • Re-combine the fractions
  • Repeat 9 times

12
Soil divider
  • Results shows that reduction made by different
    persons may give different results
  • It may be useful that working quality of the
  • soil divider and persons doing the reduction are
    checked regularly

13
Hand halving method
  • Strictly restricted to the genera that are listed
    in the Rules (2.5.2.2.4)
  • Trees and shrubs Acer, Aesculus, Ailanthus,
    Castanea, Cedrela, Corylus, Fraxinus, Juglans,
    Liriodendron, Platanus, Populus, Quercus, Salix,
    Tectona, Ulmus
  • For all other species it can be used only to
    obtain a working sample for health tests

14
Spoon method
  • Recommended method sample reduction for seed
    health testing
  • Can be used for all the seeds smaller than wheat
  • Seed is taken at least from five random places

15
Thank you for your attention!
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