Threshing – traditional methods mechanical threshers – types-principles and operation-moisture content –measurement –direct and indirect methods – moisture meters – equilibrium moisture content. Harvesting For paddy, harvesting refers to the cutting and gathering of panicles attached to the stalks. Harvesting at the right time and in the right way maximizes grain yield and minimizes grain losses and quality deterioration. Once the plants have reached full growth (approximately three months after planting) and the grains begin to ripen-the tops begin to droop and the stem yellows-the water is drained from the fields. As the fields dry, the grains ripen further and harvesting is commenced. Stage of harvest : Many factors must be considered to obtain optimum rice harvest. The grain must be mature, high in quality and have proper moisture content. Field should be sufficiently dry to support harvesting and transport. Timely harvesting ensures good grain quality, high market value and improved consumer acceptance. The right stage for harvesting is when about 80% panicles have 80 % ripened spike lets and their upper portion is straw colored. The grain contains about 20% of moisture. Rice should be harvested when the grains on lower part of the panicle are in hard dough stage. Maturity may be hastened by 3-4 days by spraying 20 % NaCl a week before harvest to escape monsoon rains Harvesting methods : Depending on the size of the operation and the amount of mechanization, rice is either harvested by hand or machine. The different harvesting systems are as follows: Manual harvesting Manual harvesting makes use of traditional threshing tools such as threshing racks, simple treadle threshers and animals for trampling or by hand using sharp knives or sickles. Gives 55-60 % grain recovery. Manual harvesting and machine threshing Rice is manually threshed, then cleaned with a machine thresher. Machine reaping and machine threshing A reaper cuts and lays the crop in a line. Threshing and cleaning can then be performed manually or by machine. Combine harvesting The combine harvester combines all operations from paddy harvesting to rice extraction - cutting, handling, threshing and cleaning. Gives 50 % recovery. Average yield : A well-managed crop of mid-late duration varieties yield about 60-70 quintals/ ha. Short duration varieties yield about 45-55 quintals. About 40-60 quintals/ ha of fodder also becomes available per season. Top Post Harvest Technologies Threshing Threshing is the process of beating paddy plants in order to separate the seeds or grains from the straw. To maintain the high quality of the harvested grains, it should be threshed immediately after harvesting. Avoid field drying and stacking for several days as it affects grain quality due to over drying. Stacked grains of high moisture content results in discoloration or yellowing. Threshing can be done manually or mechanically Manual threshing The manual methods of thr

1. POST- HARVEST
TECHNOLOGY
THRESHING

2. Presented By
Arul.S
MRT22PGMAT001
Department of
Agricultural Technology
SHOBHIT UNIVERSITY
Meerut, UP.

3. CONTENTS
1. Introduction
2. Threshing
3. Traditional Methods
4. Mechanical Threshers
5. Types
6. Principles And Operation
7. Moisture Content
8. Measurement
9. Direct And Indirect Methods
10. Moisture Meters
11. Equilibrium Moisture Content
12. Conclusion

4. Introduction
 Post harvest processing technology or Post
harvest technology of agricultural products
refers to the processes and treatments carried
out on agricultural products after it is
harvested.
 It starts from the selection of proper harvest and
ends with marketing.
 The following operations such as threshing,
drying, storage, parboiling, milling, sorting,
grading, oil extraction, juice extraction, ginning,

5.  It is an inter-discipline “science and technique”
applied to agricultural produce after harvest for
its production, conservation, processing,
packaging, distribution, marketing, and
utilization to meet the food and nutritional
requirement of the people in relation to their
needs.
 It has the capability to meet food requirement of
growing population by eliminating avoidable
losses, making more nutritive food items from

6. Threshing
 The operation of detaching the grains from the ear
head, cob or pod is called threshing. It is basically
the removal of grains from the plant by striking,
treading or rupturing.
 The traditional method of threshing using manual
labors requires 150-230 man-h/ha.
 Threshing is normally done after the grain moisture
content is reduced to 15 to 17%.
 In various parts of world, threshing is accomplished
by treading the grains under the feet of animals or
under the tractor tires, striking the grains with
sticks, pegs or loops and removing the grains by
rubbing between stone or wooden rollers on a
threshing floor or between the rasp bar and a
concave of combine.
 The threshing can be achieved by three methods:
Rubbing action, Impact and Stripping.

7.  Threshers are the most important component
of farm mechanization.
 If threshing is not done timely, all efforts made
by farmers and inputs given to crop goes
wasted.
 Traditional method of threshing by animal is
very slow.
 It gives low output. Due to low output, the
cost of operation is high and there is a huge
loss of grains because of rodents, birds,
insects, wind, and untimely rain and fire
hazards.
 Wheat threshers overcome these difficulties to
a great extent. Wheat threshers are of two type

9. Traditional Methods
I. Pedal thresher
II. Trampling
III. Threshing Rack
IV. Flail

10. Pedal thresher
o The pedal or treadle thresher consists of
threshing drum, base, transmission unit and
a foot crank.
o When pedaled, the threshing drum rotates
and rice can be threshed when panicles are
applied against the threshing drum.
o Because small straws, chaff, and foreign
matter drop along with the threshed grain,

12. Trampling
o This involves the use of bare feet or animals to
thresh the crop.
o The crop is spread over a mat or canvass and
workers trample with their own feet or use their
animals.
o Animal treading or trampling is normally carried out
at a designated location near the field or in the
village. In some regions, animals have been replaced
by tractors.
o After animal treading, the straw is separated from

14. Threshing Rack
o The crop is held by the sheaves and beats it
against a slatted bamboo, wooden platform,
or any other hard object such as a steel oil
drum.
o This is very labor intensive.

16. Flail
o A flail thresher, also known simply as a flail, is a type of
agricultural tool used for threshing, which is the process of
separating grains from their husks or stalks.
o The flail consists of a long handle with a shorter stick
attached by a short piece of chain or rope.
o The shorter stick, called the "swingle" or "beater," is used to
strike the harvested crop, such as wheat or barley, causing
the grains to separate from the stalks or husks.
o This manual method of threshing was widely used before
the invention of mechanized threshing machines and is still
employed in some traditional or small-scale farming

18. MECHANICAL THRESHERS
Mechanical threshers have revolutionized
agricultural practices worldwide. These machines
efficiently separate grains from their stalks,
significantly reducing the labor required for this
task. By employing rotating drums or cylinders
equipped with beaters or teeth, mechanical
threshers swiftly and thoroughly strip grains from
plants. Their adjustable settings allow farmers to
adapt to different crop varieties and conditions,
enhancing versatility. Moreover, mechanical

19. TYPES
I. Drummy Type
II. Olpad thresher
III. Paddy Threshers
IV. Multi-crop Threshers
V. High Capacity (Harambha)
Threshers
VI. Sunflower thresher
VII.Spike Tooth Type

20. DRUMMY THRESHER
o These threshers were very popular in the
beginning when threshers were introduced
because of its simplicity and low cost.
o The radially arranged arms known as beaters are
mounted on the shaft .These are made of mild
steel square section with mild steel flat welded
or bolted at the top.
o The beaters revolve inside an enclosed casing.
Ribs are provided inside of upper half of the
cover in order to have better threshing.

21. o Crop receives impacts from the
rotating beaters till size is reduced to
pass through concave.
o The clearance between beater and
concave is kept about 18-20 mm.
o The crop should be well dried before
feeding in the thresher. A wet crop
raps around the beater shaft and
machine becomes overloaded.
o These threshers do not have provision
for separation and cleaning of grains.
o The threshed material is later
separated and cleaned by small pedal

23. OLPAD THRESHER
o ‘Olpad’ threshers (Fig. 6) are also used for threshing
wheat crop.
o A pair of bullocks pulls it around over the dried crop
spread in a circular form on the threshing ground.
o Threshing is continued till the entire material
becomes a homogeneous mixture of grain and
‘bhusa’ (chaff).
o It consists of about 20 circular grooved discs each of
45-cm diameter and 3-mm thickness placed 15 cm
apart in three rows.

24. o An operator’s seat is provided on the
frame to control the movement of
animals.
o All discs are mounted staggered to
give more effective cutting of the
straw. It has 3 or 4 wheels to
facilitate its movement from one
place to other.
o Threshing by this thresher is fairly
efficient and cheap but is quite slow
with low output capacity.

26. PADDY THRESHERS
o Paddy thresher of pedal operated type consists of mainly
a well-balanced cylinder with a series of wire loops fixed
on wooden slates.
o It has got gear drive mechanism to transmit power. While
cylinder is kept in rotary motion at high speed, the paddy
bundles of suitable sizes are applied to the teeth.
o The grains are separated by combining as well as by
hammering action of threshing teeth. Paddy is threshed
due to impact and rubbing action between threshing
drawn loops and concave screen.
o The grains are cleaned with the help of a fan and cleaned

28. MULTI-CROP THRESHERS
o the Indian farmers raise variety of crops as
per the suitability of particular region,
climate and soil conditions, there was need
to thresh all these crops for timelines of
operation.
o Developing a multi crop thresher has solved
this problem. It can thresh crops like wheat,
moong, paddy, grain, soybean etc.

29. o For paddy, farmers need long straw.
For pulses, seed damage should be
minimal; as damaged seeds lower the
quality and causes spoilage in storage.
o The crop factors such as moisture
content, grain size, grain-straw ratio,
condition of straw etc. influence the
design consideration of main
components of threshers.
o The farmer is primarily interested in
end product, low cost, durable and
reliable machine.

31. HIGH CAPACITY (HARAMBHA)
THRESHERS
o It is a basically a chaff-cutter type thresher.
o It consists of a threshing cylinder, concave, two
aspirator blowers, reciprocating sieves, feeding
chute, feeding conveyor, feed rollers, safety lever
in the feeding chute and flywheel.
o A platform is attached to the main frame of
thresher, on which a person stands and feeds
the crop into thresher.
o All the crop materials are fed through the

32. o A safety lever provided in feeding
chute prevents the entrapping of
hands by the feed rollers.
o Threshing cylinder has two chaff-
cutter type blades and beaters.
Chaff-cutter blades cut the crop into
pieces and beater helps to detach
grain from crop.
o All the threshed materials pass
through the concave where it is
subjected to aspiration action of

34. SUNFLOWER THRESHER
o It consists of a threshing cylinder, concave,
casing fitted with louvers, cleaning system,
feeding hopper and frame .
o The cylinder concave clearance is 40 mm and
is uniform throughout its length. The
diameter of cylinder is 65 cm and length 150
cm.
o The first part of cylinder of length 133 cm

35. o The cylinder casing is of hexagonal
shape and is fitted with 7 louvers.
o The louvers help the crop to move
axially and the crop is rotated three and
half times for complete separation of
grains.
o The cleaning system has a blower and
two sieves. The opening of top sieve is
16 mm and of lower sieve 6 mm.
o Recommended cylinder and blower
speeds are 300-350 rpm and 1200-1400
rpm respectively. A tractor or 7.5 hp
motor can operate machine.

37. SPIKE TOOTH TYPE
o A spike-tooth thresher is a type of agricultural
equipment used to separate grains, such as wheat,
barley, and oats, from their husks or stalks.
o It typically consists of a rotating cylinder or drum
with spiked teeth or bars, which grab onto the stalks
and pull them through a concave surface.
o As the stalks are pulled through, the grains are
dislodged from the husks or heads.
o The spikes or teeth help in breaking the husks apart,

38. o This type of thresher was historically
used in manual or animal-powered
agricultural settings before the advent
of mechanized farming equipment.
o While it has largely been replaced by
more modern combine harvesters in
commercial agriculture, spike-tooth
threshers are still used in some
traditional or small-scale farming
operations.
o They are valued for their simplicity,

40. MOISTURE CONTENT

41. OBJECTIVE OF DRYING
o It preserve perishable products against
spoilage by reducing water activity.
o Permits continuous supply of product
through out the year
o It increases shelf life of products.
o To reduce cost and difficulty of packaging,
handling, transportation and storage.

42. DRYING THEORY
o It is the removal of moisture content to a
recommended level due to difference in
vapor pressure between the product and
atmosphere.
o Dry matter of the commodity remains
constant.
o Hygroscopic material enter into falling rate
period faster then non-hygroscopic material.

43. o Generally moisture content is measured in
wet basis for industrial purpose.
o For plotting drying curves moisture content
dry basis is used.
o Moisture content dry basis is always greater
than moisture content wet basis.

45. MOISTURE CONTENT
DETERMINATION METHODS

46. DIRECT METHODS
1. Hot air oven method
2. Vacuum oven method
3. Balance
INDIRECT METHODS
1. Electrical resistance method
2. Dielectric method
3. Chemical method

47. EQUILIBRIUM MOISTURE
CONTENT-EMC
 It is the final moisture content attained by
the hygroscopic product.
 The grain will gain moisture if the outside
vapor pressure is higher and will loose
moisture if outside vapor pressure is lower

48. o The moisture content attained by the grain
with respect to a set of atmospheric
temperature and RH such that the grain
moisture is in equilibrium with the
surrounding air is called EMC of the product.
o EMC is generally expressed in dry basis.
o If the air is having 0 % humidity then EMC
=0.

49. FACTORS AFFECTING EMC
1. Type of product
2. Variety of product
3. Maturity
4. Temperature and RH of surrounding air
It can be calculated using Henderson’s

50. EMC CAN BE CALCULATED USING
HENDERSON’S EQUATION
1-RH = exp(-c.T.Mn)
Where
RH= relative humidity in decimal
C, n= constants
T= temperature in kelvin
M= EMC

51. TYPES OF MOISTURE
1.Free moisture
 The moisture that is present in excess of equilibrium
moisture is known as free moisture.
 It is the difference between the initial moisture content
and EMC under given drying conditions.
2.Bound moisture
 it is the equilibrium moisture of a product at 100% RH.
3.Unbound moisture
 the moisture present in product in excess of bound
moisture is called as unbound moisture.

52. THANK YOU…
Any Queries:
S.Arul
6374120823
arulsivakumar489@gmail.com