seed moisture content, different methods of moisture testing, moisture content standards of agricultural crops according to Indian Minimum Seed Certification Standard

1. PRINCIPLES AND PROCEDURES
of
Seed moisture TESTING
Prof. Kumari Rajani
Department of Seed Science & Technology
Bihar Agricultural University
Sabour, Bhagalpur-813210

2.  A small change in seed moisture
content has a large effect on the
storage life of the seeds
 Seeds may sprout or molds may
develop at high levels of moisture,
and the seeds may lose viability in a
few days
 Therefore it is important to know the
moisture content in order to make a
reasonably accurate prediction of
the possible storage life of each
seed sample stored
Why is it important to determine moisture content?
Prof. Kumari Rajani, DSST, BAU, Sabour

3.  Seed moisture content is one of the most important
factor influencing seed quality and seed storability
 The seed moisture content is the amount of water
present in the seed
 It is usually expressed in percentage and calculated either
on wet or dry weight basis
 In Seed Testing Laboratory, it is estimated on wet weight
basis
Prof. Kumari Rajani, DSST, BAU, Sabour
Seed Moisture Testing

4. The optimum method for moisture testing depends upon:
1. Chemical composition of seed
2. Seed structure
3. Moisture content level
4. Degree of accuracy and precision required
5. Constraints of time
6.Technical expertise and cost
The ideal methods could be:
 Adopted to all seeds
 Measures moisture content from 0 to100 percent
 Reproducible
 Require less training
 Low in cost
Prof. Kumari Rajani, DSST, BAU, Sabour

5. It is impossible to combine all these. However, in order
to measure the moisture content of seeds, methods
can be broadly grouped in two categories:
a) Direct method
b) Indirect method
Prof. Kumari Rajani, DSST, BAU, Sabour

6. “The seed moisture content is measured directly by
removing moisture and then by measuring weight loss”
1. Oven-drying method
2. Phosphorus pentaoxide method
3. Desiccation method
4. Vacuum drying method
5. Distillation method
6. Karl Fisher's method
7. Direct weighing balance
8. Microwave oven method
Direct method
Prof. Kumari Rajani, DSST, BAU, Sabour
Hot Air-Oven method is most
commonly used because it is
economical, requires simple
equipment and little
technical expertise, and can
be used with any kind of
seeds at any moisture
content

7. Commonly used methods are based on electrical
property of seed. An electrical current unit, resistance
or capacitance, is measured and then converted into
moisture content
These are not so accurate method and measures do not
give moisture content of the seed directly
Estimation is approximate, but convenient and quick in
use
These are frequently used at seed processing plants
Indirect method
Prof. Kumari Rajani, DSST, BAU, Sabour

8. Quick, convenient and non-destructive method
Moisture determination is approximate (Not precise)
Moisture is determined by electrical conductivity or electrical
resistance of seed (moisture content is directly proportional to
the resistance and dielectric constant of the seed sample)
Moisture determination by Moisture Meter
Prof. Kumari Rajani, DSST, BAU, Sabour
Widely used method to measure seed moisture
in field and during processing of seed
Needs calibration for each species

9.  Hot Air-oven methods: commonly used for moisture
determinations
 The air ovens are electrically heated and the air within
them is at atmospheric pressure and is circulated by
convection with the help of fan or mechanical means
 The basic reference method for the introduction of a
new species and methods into the Rules is the low-
constant temperature oven method
Basic Reference Method for Determination of Moisture Content
Prof. Kumari Rajani, DSST, BAU, Sabour

10. Constant Temperature Oven Method
1. High-ConstantTemperature Oven Method
Temperature : 130–133°C
Duration : 4 h ±12 min for Maize
2 h ± 6 min for Other Cereals
1 h ± 3 min for Other Spp.
2. Low-Constant Temperature Oven Method
 Temperature and Duration: 101–103°C for 17 ±1 h
 The RH of the laboratory should be ≤70% during moisture
testing
 Suitable for seed species with high oil/volatile content
Ex: Onion, Soybean, Groundnut, Mustard, Chilli, Cotton,
Linum, Castor, Til

11. The methods prescribed are designed to reduce
oxidation, decomposition or the loss of other volatile
substances while ensuring the removal of as much
moisture as possible
Principle for Determination of Moisture Content
Prof. Kumari Rajani, DSST, BAU, Sabour

12. Grinding mill Hot Air-Oven
Moisture Containers
Glass
Tin
A glass desiccators
with silica gel
Analytical balance
Materials Required for Moisture Determination

13. The submitted samples must be sealed in moisture proof
container or polythene bags of ≥700 gauge
Size of submitted sample:
100 g: for species that have to be ground
50 g: for all other species
Seed should not be exposed in environment for more than 2
minutes
The oven must be electrically heated 30 minutes before keeping
the samples
The determination must be carried out in duplicate on two
independently drawn working samples
Important facts to be remembered…
Prof. Kumari Rajani, DSST, BAU, Sabour

14. The weight of sample depends on the diameter of the
containers used:
Diameter >5 cm and <8 cm: 4.5 ±0.5 g
Diameter ≥8 cm: 10.0 g ±1.0 g
Containers must be of metal dishes or glass dishes with lids
(non-corrodible materials)
The desiccator must contain an effective desiccant i.e. silica gel
The balance must be capable of weighing to an accuracy of at
least ±0.001 g or 1mg
Prof. Kumari Rajani, DSST, BAU, Sabour

15.  The necessity for grinding depends on factors such as seed size
and seed coat permeability to water
 Large seeds: cereal seed, beans, and peas
 Small seeds: do not require grinding
 In case of high moisture content or an extremely hard seed coat,
which may prevent grinding: breaking or cutting the seed into
pieces ≤7 mm across is permissible
 The grinding mill must be made of non-absorbing material and
easy to clean
Test Necessity for Grinding
Prof. Kumari Rajani, DSST, BAU, Sabour

16. Procedures of Moisture Determination
(Hot Air-Oven Method)

17. Label moisture
containers and lid with
the same specification
weigh moisture
containers with lid
(M1)
Weigh seed samples
according to the
diameter of the container
(weighing should be upto 3 decimal places)
Weigh moisture
container with seed
samples and lid
(M2)
Keep in heated oven
at set temperature for
the time required for
the species
Take out from oven and
keept in desiccator for 45
minutes
Weigh moisture container
with seed samples and lid
(M3)
Calculate moisture content
and report
Prof. Kumari Rajani, DSST, BAU, Sabour

18. The moisture content as a percentage by weight must be
calculated to three decimal places for each replicate by
following formula:
M2-M3
Moisture Content (%) = X 100
M2-M1
Where,
M1: weight in grams of the container and its cover
M2: weight in grams of the container, its cover and seed sample
before drying, and
M3: weight in grams of the container, its cover and seed sample
after drying
Calculation and Expression of Results
Prof. Kumari Rajani, DSST, BAU, Sabour

19. Groundnut (>17%) and paddy (>13%):
 Take two subsamples, each weighing 25±1 g are placed in weighed
containers
 The two subsamples, in their containers, are then dried at 130°C for
5 to 10 min
 The partly dried material is then kept exposed in the laboratory for
at least 2 h
Very moist seed of Zea mays (>25% moisture content):
 The seed is spread in a layer not deeper than 20 mm and dried at
65–75°C for 2–5 h
Other species with a moisture content >30%:
Samples should be dried overnight in a warm place
If pre-drying is obligatory…
Prof. Kumari Rajani, DSST, BAU, Sabour

20.  After predrying, the subsamples are reweighed in their containers
to determine the loss in weight (Considered as S1)
 The second stage drying (S2) of sample should be carried out by
following routine air-oven method
Original moisture content of the sample should be calculated as a
percentage by following formula:
S1 X S2
Moisture Content (%) = (S1 + S2) -
100
Where,
S1: moisture lost in the first stage drying
S2: moisture lost in the second stage drying
The result of a moisture content test must be
reported in % upto one decimal place
Prof. Kumari Rajani, DSST, BAU, Sabour

21. Maximum Seed Moisture Percent for Storage under
Ambient Condition and Vapour Proof Container
Crops Ambient storage Vapour proof container
Paddy 13 8
Barley, Wheat, Triticale, Maize, Sorghum,
Pearl millet, Minor Millets, Oat,Teosinte
12 8
Soybean 12 7
Mesta 10 8
Berseem, Luncerne 10 7
Cotton 10 6
Black gram, Bengal Gram, Cowpea, Green
gram, Horse gram, Indian bean, Khesari,
Lentil, Mothbean, Pea, Pigeon pea, Cluster
Bean, Rice bean, Sunhemp
9 8
Rajmash (French bean), Linseed, Safflower,
Sunflower, Jute
9 7
Groundnut, Niger, Sesame 9 5
Rapeseed 8 7
Castor, Mustard, Taramira 8 5
Tobacco 5-6
Prof. Kumari Rajani, DSST, BAU, Sabour