4. Reasons for post harvest losses
1. Poor product coming into storage
2. Poor storage management
3. Poor quality paddy + poor milling techniques
5. Seed Deterioration
Seeds lose half their storage life for every 1% increase in
seed moisture between 5 and 14%.
Seeds lose half their storage life for every 5 degrees C
increase in storage temperature between 0o and 50oC.
6. Principles of seed storage
In the natural environment and when stored at ambient room
conditions, seeds respond to constantly changing relative
humidity and temperatures. Maintaining seeds under controlled
conditions lowers metabolic activity, thereby reducing the aging
process and increasing longevity of the seed lot.
For most seeds, a cool and dry environment is preferred and for
orthodox seeds the cooler and drier the environment, the
greater the longevity that can be achieved.
7. The five most important factors affecting seed
longevity are
1. Seed type
2. Seed quality
3. Integrity of the protective seed coat
4. Seed moisture content
5. Storage environment
8. Seeds are generally categorized into the following
types
Orthodox:
Seeds that can be dried, without damage, to low moisture contents, usually much
lower than those they would normally achieve in nature. Also called long lived
seeds. Tolerate desiccation (no loss in viability) to 5% moisture content or below.
Ex: Rice, Maize etc.
Intermediate:
These seeds can also be stored for longer period, but it cannot withstand low
temperature, and they generally lose viability more rapidly at low temperature.
Tolerate desiccation to about 10–12% moisture content.
Ex: Legumes, papaya, citrus.
Recalcitrant:
Seeds that do not survive drying to any large degree, and are thus not amenable
to long term storage.
Killed by desiccation to 15–20% moisture content. Ex: Mango, Jack etc.
9. GUIDELINES FOR SUCCESSFUL SEED STORAGE
1. Determine whether the seeds can be stored. (Not all
seeds can be stored successfully.)
2. Collect healthy, ripe seeds.
3. Separate and clean the seeds.
4. Dry the seeds to the correct moisture level for storage.
Meanwhile, germinate some of the seeds to make sure
that they are good. Pack the seeds for storage.
5. Store the seeds.
6. If you store the seeds for a long time, germinate a
sample from time to time to make sure that they are still
good.
10. Maintenance during seed storage
1. Maintain Cool Conditions
Keep seeds out of direct sunlight in a cool spot that maintains a fairly
consistent temperature.
Store in a cold closet, a basement, or a room on the north side of your
home that remains cool year round.
Freezing isn’t necessary for short-term storage, but you can
refrigerate seeds, provided they are sufficiently dry.
11. 2. Maintain Dry Conditions
To germinate all seeds need sufficient water and temperatures that
are favourable for plant growth.
Make sure your seeds don’t sprout by storing them in a spot that isn’t
humid and ensure the seeds are dry before sealing them in a
container.
While storing in freezer, if seeds
are too wet, they can rot in the
refrigerator or suffer frost
damage in the freezer.
Hence place the packets in an
air-tight container and ensure
the seeds are properly dried to
begin with.
12. Germination mechanism
1. Imbibed water stimulates
Gibberellin synthesis.
2-3. Gibberellins diffuse to the
aleurone layer and stimulate the
synthesis of enzymes.
4-5. Enzymes break down the starch
and the sugars are transported to
the developing embryo.
13. 3. Protect the Seeds
Bacteria, fungi, mites, insects, rodents and birds may affect
the seeds in storage.
Bacteria do not show any significant effect on the stored seeds,
since it needs water for its proliferation.
Storage fungi like Aspergillus and Penicillium infect the seeds
and produce mycotoxins that will deteriorate the seed quality.
Insects and mites cause severe damage especially in warm and
humid conditions.
Birds and rodents cause huge loss of seeds during storage
period.
14. The general RH and temperature for multiplication
of various biological organisms in seed storage is
as follows
Organism Optimum temperature (0c) Relative humidity (%)
Insects 27-37 30-95
Mites 19-31 60-100
Fungi 20-40 60-100
Microbes 26-28 91-100
15. Natural Products Used in Storage Pest Control
1. Neem products in pest control
Take required amount of neem and pongamia leaves and shade dry it
till it becomes papery. Seeds are filled up to ¾th of a storage bin and
covered with a clean cloth. Mix the above leaves and spread a handful
on the surface of the seeds in the storage bag or bin.
Neem oil can be mixed with the seeds at
the rate of 2% by the weight of the seed.
Using oil is more effective than the
leaves.
Seeds can be stored by mixing with Neem
oil (2-3 ml / kg of seed). 50 kg gunny bags
of any seeds need 150 ml of the oil for
mixing.
16. 2. Other plant products in pest control
Mix the seeds of Maize, Wheat etc., with dried fruits and leaves of
Vantulsi (wild Tulsi - Ocimum) at the ratio of 1:100 to prevent from
the weevils in storage.
Mix blackgram seeds with mustard oil @ 10-15 ml per kg of seeds and
store it in earthen pots covered with dry cloth.
3. Wood ash in storage pest control
Wood ash is a safe and effective pest control material. Mix equal
quantity of seed and wood ash to prevent the attack of beetles and
other storage pests.
17. The use of fumigants
Fumigants are toxic gases used to disinfest a commodity in an
enclosure which, ideally, is completely gaslight. Fumigation
enclosures should certainly be sufficiently gaslight for the gas to
penetrate and remain in the commodity for long enough to kill all
stages of the insects present in or amongst the grains.
The purpose of a fumigation is to obtain a more-or-less immediate
disinfestation of the commodity and the space enclosing it.
Ex: Phosphine and methyl bromide
18. RODENT CONTROL
Rats eat food grains and seeds that are stored in the house and also in
the storage godown. They shed droppings on the grain while they are
eating it and can also spread diseases like plague, rat fever etc., in
human beings which are quite dangerous.
Physical Methods
1. Rat proofing:
The rat problem can be solved to a great extent if the entry of rats is
prevented in houses, stores and godowns. This can be done by
building rat proof godowns.
2. Mechanical traps:
In case of storage godown wooden cage or mice cage can be used for
the control of rats. Bait is used in the trap to attract the rat to come
into the trap. Bait may be any food like pieces of meat, dried fish,
bread etc., that rats like to eat.
19. RODENT CONTROL
3. Indigenous methods of rat control
Place unripe papaya fruit pieces in the corner of the storage godown.
When rats eat these fruits, the mouth tissues get damaged due to the
chemical substance in the papaya fruit. For one room, we can keep 2-
3 pieces of the fruit.
Take 2-3 kg of castor leaves and add 3 litres of water. Boil for half an
hour and filter the extract. Take 2-3 kg of sorghum seeds and add it to
the above extract. Boil it again for half an hour. Take these seeds in a
vessel and keep it in the corner of the storage rooms. Rats feed on
these and die.
4. Chemical method
Aluminium phosphide
20. Attack by microorganisms and their control
Various micro organisms affect stored grains such as fungi, bacteria,
yeast, actinomycetes and protozoa. Out of all these microorganisms
fungi is responsible for maximum damage / spoilage of seeds in
storage.
When a fungus is present, it causes off odour, kernel discolouration,
loss of nutritive value and loss in viability. Fungi may also produce
certain poisonous substances which are harmful and may be fatal to
human beings, animals, poultry etc.
Control measures
Moisture content of the seed/grain should be reduced to a safe level.
The safe level of moisture content for wheat and rice are 12% and 13%
respectively.
Reduction of temperature to a range of 23oC – 30oC helps in the
reduction of storage fungal growth.
21. Protect the Seeds cont.
Choose a storage spot that is pest-free and you can keep a
close eye on to ensure it remains that way.
Glass jars, metal containers, or wire mesh can further
protect seeds from invaders.
When using a storage area that is cool and dry year round,
you may be able to keep seeds in paper bags, mesh bags,
or envelopes in what is called “open storage”. Moisture
and heat generated by the seed during respiration can
escape through these gas permeable containers.
22. What is required for a good storage
system?
Prevention of moisture re-entering the grain after drying
Protection from insects, rodents and birds
Ease of loading and unloading.
Efficient use of space
Ease of maintenance and management.
31. Farmers Present Practices
1. Sell excess immediately after harvest (indebted or poor
storage)
2. Dry grain to 10-11% before storage
3. Take grain out and re-dry during storage period
4. Store seed in “sealed” containers
33. Commercial bag storage system
Open to atmosphere
- moisture uptake,
- pest problems
Store in batches
Clear headways and walkways
Relatively easy to fumigate
34. Commercial Bulk Storage
Not popular in Asia
Efficient use of space
Easy to control pests?-
sealed for fumigation
Less problems with rodents
and birds
35. Commercial hermetic system
Grain stored in bags
Protected against moisture
uptake and insects
Rat and pig damage?
Use as harvest management aid
Need O2 monitoring
Big potential in Tropical areas
5-300 metric tons
37. Storage Hygiene
Keep storage areas clean.
Clean storage rooms after they are emptied
Placing rat-traps and barriers in drying and storage areas.
Cats deter and help control rats and mice
Inspect storage room regularly to keep it vermin proof.
Inspect the stored seeds once a week for signs of insect
infestation.
