Corn PostHarvest

1. HARVEST AND
POST-HARVEST
OF CORN
MILAGROS C. MALINAO
PROFESSOR III (RETIRED)
UNIVERSITY OF SOUTHERN MINDANAO
KABACAN, COTABATO

2. STEPS OF SEED
CONDITIONING
Harvesti
ng
Drying
Sorting
(cobs)
Shelling
Final
Drying
Cleaning
and
Grading
Final
Sorting
Seed
Treatmen
t
Bagging
Storage

3. HARVESTING
◻ Harvesting fully mature
seed will result in
maximum yield, improved
appearance of seed, better
seedling vigor in the
subsequent crop, greater
resistance to mechanical
injury while handling in the
conditioning plant, and
reduced susceptibility to
injury from high drying
temperatures.

4. HARVESTING
◻ Corn is ready for harvesting when black layer
developed at the grain’s point of attachment
to cob; kernels are glazed, leaves and husks
are dry.
◻ To achieve good quality in most tropical
areas, harvest is done when the seeds has
dried to 20-25% level moisture content.
• 90 – 95 DAP – for early variety
• 100 – 110 DAP – for intermediate & late
maturing varieties

5. HARVESTING
Harvesting can be:
 Manual
 Mechanical
• Combine
Harvester
• Corn Picker

6. DRYING
Sun Drying
◻ Dry the corn in cobs to 18% Moisture
Content to facilitate shelling.
◻ This can be done by spreading the ears
out in thin layer on a concrete floor and
turning them for 1-2 days.

7. DRYING
Mechanical Drying
◻ Drying in a bin with
forced heated air
that does not exceed
48⁰C (120⁰F) is the
normal alternative.

8. FURNACE
BLOWER
MECHANICAL BINS

9. IMPORTANCE OF SEED
DRYING
◻ Numerous workers have pointed out that
high moisture in seed is the major factor
causing deterioration of viability and vigor
during storage.
◻ The excess moisture causes heating and
mold growth both of which are very
detrimental to quality.

10. SORTING ( in cobs)
◻ In this operation, ears are visually examined
to identify any off-types, diseased, or
damaged ears.
◻ It is an essential step in quality control and it
is important that workers selected are well-
trained and dedicated to this operation.

11. SORTING ( in cobs)
Sorting or removal of off-types, discolored, rotten or
diseased ears is done after drying if bin drying is
used.

12. SHELLING
◻ Shelling is normally done when the seed
reaches 14 to 16% moisture. Rubberized
sheller or hand shelling reduces seed
damage.
◻ Damage can occur when moisture
content of the cob is high (35% or more)
during mechanical shelling.

13. SHELLING

14. FINAL DRYING
◻ Corn seeds will be finally
dried until grain moisture
reaches 10-12% Moisture
Content.

15. FINAL DRYING
Sundrying
• Spread out the seeds on top of trapal and not directly
on the cement floor.
• Drying directly on cement floor is not recommended
due to high temperature (50 –70°C).

16. FINAL DRYING
Mechanical Drying
• the load should not exceed 24 inches
thick.
• the temperature of the bin should not
exceed 48 C (120 F).

17. CLEANING, GRADING and FINAL
SORTING
• Seed maize leaving the sheller often contains
varying amounts of foreign material including
bits of cob, husk, broken kernels, stones, dirt,
weed seeds, insect larvae, etc.
• This debris must be removed to improve seed
appearance, and to promote good storability
and plantability.
• For small volume of seeds, a modified electric
fan blower can be done.

18. CLEANING, GRADING and FINAL
SORTING
• Blowing/winnowing is still effective.
• For big volume of seeds, air screen
cleaner help removes broken kernels,
dirt, trash, cob pieces; and separates big
and small kernels.
• Maize seed is sized based on width,
thickness, and sometimes length through
a series of flat or cylindrical metal
screens which possess either round or
oblong holes.

19. CLEANING, GRADING and FINAL
SORTING

20. SEED TREATMENT
 Malathion or Decis plain can control weevil or
"bokbok".
 Ridomil can be used for seed treatment to control fungi
"alkoheris“ or downy mildew.
 CHEMICALS FOR SEED TREATMENT
• Ridomil - 2 g/kg of corn seeds
• Decis - 0.11 ml/kg of corn seeds
• Malathion - 1 ml/kg of corn seeds
• + Rosa Pink - 0.375 g/kg of corn seeds
• H2O - 4 ml/kg of corn seeds

21. SEED TREATMENT

22. SEED TREATMENT
Treated Seeds

23. BAGGING
 The final step in the conditioning process is
the packaging of seed.
 A seed package accomplishes several
essential functions including:
 Serving as a convenient unit for handling
transport and storage,

24. BAGGING
 Protecting seed against contamination and
mechanical damage,
 Providing a suitable environment for
storage,
 Providing a barier against seed loss and
escape of pesticides, and
 Serving as a sales promoter (Thompsom,
1979).

25. BAGGING
◻ Woven plastic bags are commonly used.
◻ An 18 kg seed weight per bag is now a
practice with approximately 55,555 - 60,000
kernels.

26. STORAGE
 Seed moisture content and temperature are
the two most important factors influencing
seed storability (Delouche, 1973).
 Seed biological activity increase as seed
moisture content and temperature increase.

27. STORAGE
 Growth and reproduction of undesirable seed
molds and storage insects are increased
under higher moisture and temperature
conditions.
 As seeds have the ability to take up or give off
moisture, it is essential to store them in
environments with low relative humidity.

28. HARRINGTON’S “RULE OF
THUMB”
 This rule states that for proper seed
storage the relative humidity percentage
and the storage temperature in degrees F
should add up to no more than 100.
 Examples
• 50% relative humidity (RH) and 50 ºF
• or
• 60% RH and 40 oF, and so on.

29. HARRINGTON’S “RULE OF
THUMB”
 For every decrease of 1% seed moisture content, the
life of the seed doubles. This rule is applicable when
moisture content between 5 and 14%.
 For every decrease of 5°C (10°F) in storage
temperature the life of the seed doubles. This rule
applies between 0°C to 50°C.
 Good seed storage is achieved when the % of relative
humidity in storage environment and the storage
temperature in degrees Fahrenheit add up to hundred
but the contribution from temperature should not
exceed 50°F

30. STORAGE
 Storage areas should be kept clean and free
from insects and rodents.
 Seed stored for one or two year requires 18-
20oC and relative humidity of 60-70%.
 Lower temperature and relative humidity are
required for storing seeds more than two
years.

31. STORAGE
Commercial Seed Storage
Capacity: 90 tons

32. Traditional Storage Practices
Ash Seed Treatment
◻ Studies in sorghum seeds treated with ash
with a ratio of 1 part ash : 4 parts sorghum
mixed together and stored in air tight jute
sacks showed there was no pest problem
within six months.

33. Neem Seed Kernel Extract
 Neem seeds will be powdered very well and
soaked in 100 liters of water for about 24
hours. The extract will be filtered /strained.
Jute bags to be used for storage will be
dipped in the NSKE solution for 30 minutes
and later air-dried. This was used in storing
rice seeds, pulses and oil seeds.
Traditional Storage Practices

34. Neem Leaves
 Farmers practiced an indigenous method of
storing various grains, pulses, and oil seeds
with neem leaves stored in jute bags. It is
moderately effective in protecting the grains
from pulse beetles, lesser grain borers.
Grains could be stored even up to one year.
Traditional Storage Practices

35. Experiments using Tubli Roots
 Crush tubli roots, then soak in water
overnight. Filter or strain and later mixed with
cassava flour -which will be air-dried. These
will be mixed with the corn seeds in slurry
method then later air-dried before storing in
jute bags.
Traditional Storage Practices

36. END.