Seed clining practices in farming

1. Madan Bhandari Memorial Academy Nepal (Affiliated to CTEVT)
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Seed Processing: Seed Cleaning & Drying
(3rd Year)
By
Govinda Raj Sedai
Madan Bhandari Memorial Academy Nepal
Urlabari, Morang

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Seed processing is the process of removal of undesirable materials
(weed seed, other crop seed and inert matter) and the seed is
uniformly sized, dried to safe moisture content, treated, tested and
bagged. Thus by seed processing, the physical quality of seed is
improved. Equipment's like Sheller or thresher, dryer, cleaner,
grader, gravity separator, treater, bag closer, set of screens, heat
sealers etc. are normally required to establish a small seed processing
plant.
Advantages of seed processing:
• Due to proper sizing we can get the uniformity in planting,
germination and maturity of seed crop.
• Improvement in seed marketing due to upgrading of seed quality.
• Prevention of the spread of weed.
• Protection from diseases and insects.
• Reduction in seed losses by removing high moisture content and
foreign materials from the seed.
Seed Processing

3. Madan Bhandari Memorial Academy Nepal (Affiliated to CTEVT)
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Seed scalping:
Scalping refers to the process in which the particles
which are larger than the seed size are screened out and
the seeds are separated in a vessel. It can be done by
dropping the small seeds through a hole and keeping
the larger one on top. This helps in the proper handling
of the seeds and helps prevent wastage.
Debearding:
to remove the fibrous part from the shell of a mussel
before cooking it. As you clean and debeard the
mussels, check to make sure their shells are tightly
closed.

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• As processing begins, the first phase consists of scalping,
debearding, hulling, shelling or any other operations
necessary to make the seed flow more readily through
cleaners and elevators.
• The second phase includes removal of inert matter;
weed seed, other crop seed and broken seed that are
larger or smaller than the normal size of seed.
• This is done by the air screen cleaner but may include
one or two other basic machines.
• After desired purity obtained, seed enter the final
processing phase- drying, treating and bagging and get
ready for marketing.
Seed Cleaning

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Seed cleaning :
• Cleaning is the process of the separation of
undesirable material i.e. inner matter, weed seeds,
other crop seeds, light and chaffy seeds, off sized,
damaged or deteriorated seed from desirable
materials.
• This is done on the basis of differences in physical
properties of desirable seed and undesirable
matter.
• The principle physical differences found in seeds are
seed size, density, shape, surface texture, colour
etc.

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There are three methods or steps, which are adopted in
seed cleaning.
• Pre-conditioning and pre cleaning,
• Basic seed cleaning,
• Upgrading the quality of cleaned seed.
1. Pre-conditioning and pre cleaning:
Pre conditioning refers to the operations performed to
prepare the seed lots for basic seed cleaning e.g.
shelling, debearding etc. In pre-conditioning the pieces
of trash, stones, clods, which are larger or lighter than
the desirable size and weight of seeds are removed.
SEED CLEANING

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2. Basic seed cleaning:
It refers to the actual cleaning and grading of
seeds. Many types of seeds can be completely
cleaned and made into a finished product by
basic cleaning. Basic seed cleaning is done
over an air screen machine, which is called air
screen cleaner. It is a basic seed cleaning
equipment's of the seed processing plant

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3. Upgrading the quality of cleaned seed:
The various processing operations conducted after
basic cleaning operation to further improve seed
quality are regarded as upgrading operations. This
practice is done to further upgrade the seed quality
by removing either specific condiments, or by very
precise size grading. The choice of upgrading
operation depends upon the type of contaminants and
crop seed. Different types of screens are used in
cleaning seeds.

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• Drying of seed lots i.e. lowering down seed moisture
content to safe moisture limits, is very important in order
to maintain seed viability and vigour which may otherwise
deteriorate fast due to mold growth, heating and increased
microorganisms.
• For production of high quality seed drying for effective
seed storability and longevity is very important. At
maturity stage, the moisture content of the seed is quite
high (upto 45%). It has to be reduced to a safe level
weather it has to be stored for short or long period. For
short term storage (upto 9 months) the seed should be
dried to a moisture content of 8-10%. For storage upto
three years, it has to be dried to 6-8%. High moisture
content during storage is undesirable.
Drying of seed

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• Seed is living hygroscopic material, its moisture content
depends upon the relative humidity and temperature of the
air. Whenever the vapour pressure within the seed is
greater than that of the surrounding air, vapour will move
out of the seed and vice versa. When the two vapour
pressure are equal, there is no net movement of vapour, at
which point the moisture content of the seed is in a state of
equilibrium with the surrounding atmosphere. Drying air
temperature higher than 43oC are injurious to seed quality.
Drying of seed

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Advantages of seed drying
• Seeddryingpermitsearlyharvest.
• Permitslongtermstorage.
• Permitsefficientuseoflandandmanpower.
• Permitsuseofplantstalksasgreenfodder.
• Permitsseedsmentosellabetterqualityproduct.
Methods of seed drying
There are mostly two methods of seed drying, which are:
• Sun drying
• Forced air drying
– Natural air drying,
– Drying with supplemental heat,
– Heated air drying.
Drying of seed
Seed moisture content % Storage life
11-13 ½ year
10-12 1 year
9-11 2 year
8-10 4 year

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Six months storage
Without beads
69% infestation
With beads
0% infestation
Bead-dried seeds were not consumed by bruchids.
Courtesy K. Kunusoth, ANGRAU, Hyderabad, India
Drying Prevents Insect Damage in Storage

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A. Sun drying: This method involves for reducing the moisture
level of crops before harvest, after harvest and threshing of seeds on
the threshing floor in a couple of days. Main advantages of sun
drying are that it requires no additional expenditure; some diseases of
seeds can also be controlled by sun rays and this technique is known
as heliotherapy. The disadvantages are delayed harvests, risk of
weather damage and increased likelihood of mechanical admixture.
During sun drying the produce should not spread on wet, dirty and
kachha threshing floor and to avoid mechanical admixture only one
crop variety should be handled in a threshing floor.
Drying of seed

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B. Forced air drying
In this method natural or heated air is forced in to seeds.
The air passing through damp seeds picks of water. The
evaporation cools the air and the seed. The heat necessary
for evaporating the water comes from the temperature drop
of the air. This is the most fundamental principle of forced
air seed drying. There are generally three methods of forced
air drying which are:
– Natural air drying: Natural air is used in this type of
drying method.
– Drying with supplemental heat: Small quantities of heat
to raise temperature about 10-20oC for reducing RH are
provided in this method, so that drying can take place.
– Heated air drying: In this method the drying air is
heated considerably as much as 110oF (43oC).

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Fig: IRRI-type hot air drier

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What are Drying Beads?
• ceramic product
• crystalline
structure
• micro porous
material
• uniform pore
dimensions
• thermally very
stable
• mechanically very
stable
SPECIFIC PORE SIZE FOR
WATER (3Å)
100% REGENERATION AT
250˚C

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DrumDry
&
DryBox
SeedVaul
t &
DryStore
Drying
Beads &
MobiDry
FlexiDr
y &
SiloSafe
QualiDr
y

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What is MobiDry?
MobiDry is the DIRECT use of drying
beads for drying produce.
The action mechanism is still indirect
(drying beads are reducing the
moisture content of the air, and every
product in an environment will strive
to an equilibrium with that
environment.
The beads can be mixed (fastest) or
added through a net or separated
through other methods (sieve, open
and perforated can…)

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DrumDry & DryBox
What is DrumDry
(or DryBox)?
One possible
application

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What is DrumDry (or DryBox)?
We do know that there is a
direct link between the
product and his environment.
As soon as the water balance is
in equilibrium, we can measure
the equilibrium RH of the
environment and through the
correct isotherm (or through
the Cromarty equation)
calculate the moisture content
of the product.
We do know that for seeds and
grains this equilibrium will be
reached relatively fast (hours)
We can therefore pre-calculate
some safe, risky or bad zones
so that the use of this system is
easy and straightforward.
Every product is
in an active
equilibrium
with his
environment
Influx = Outflux
equilibrium
Influx > Outflux
e.g. imbibition
Influx < Outflux
e.g. drying