This document provides information about seed drying principles and methods. It discusses that drying seeds reduces moisture content to allow for better storage and prevents microbial growth. The main methods covered are sun drying and forced air drying. Forced air drying uses fans to circulate dry or heated air through seeds to evaporate moisture based on air temperature and humidity levels. Recommendations are provided for optimal drying temperatures and depths for different seed types, as well as safe moisture contents for storage.

1. Sub.:- Principles of Seed Technology
Course No. :- APB- 5221
Credit hours:- 3(1+2)
Lec. Topic :- Principles of Seed drying
Presented by:-
Indira Gandhi Krishi Vishwavidyalaya
Raipur, C.G.
Presented by:-
Lt. Roshan Parihar, Asstt. Professor (GPB)
Deptt. of Genetics & Plant Breeding
BTC College of Agriculture & Research Station
,Sarkanda, Bilaspur,(CG)-495001

2. PRINCIPLE OF SEED DRYING
• DRYING : It means to say that a process of
reducing the moisture content of seed to such
an extent which permits its better storage
conditions.
• It maintain seed viability and vigour.
• It prevents the microbes to grow on seed
surface.
• It reduces the internal heat of the seed and
prevent the metabolic activity of seed.

3. Other advantages of seed drying
• It permit early harvest.
• It permits long time storage.
• It permits more efficient use of land and
manpowermanpower
• It permits use of plants as green fodder.
• It permit seedsmens to sell a better quality
product.

4. Methods' of seed Drying
• 1. Sun Drying :Drying of raw seeds under natural
sunlight under the concrete floor.
• Its adv.:- It is a cheap method and need no
additonal expenditure for investment.
• Its process:-
• Crops at harvest maturity are harvested .• Crops at harvest maturity are harvested .
• Harvested crop get kept on field for sun dry for 2
days and then kept for threshing and winnowing
operations.
• Winnowed crop again spread on concrete floor as
a thin layer and dried for reduction of moisture
content to a safer limits.

5. • Its disadv.:-
• Delayed harvesting of a crop may have a risk
of weather damage or have a risk of
mechanical admixture.
• Precautions for sundrying:-
• Don’t spread the produce on wet or kuccha• Don’t spread the produce on wet or kuccha
floor,dirty and dustuy floor because the
hygroscopic nature of seed absorb the
moisture of wet floor.
• One crop variety produce should be handled
separately to avoid amixtures.

6. FORCED AIR DRYING
• The method of applying forced air with natural heat or
artificial heat for the drying of seed is called as forced
air drying.
• The principle of forced air drying are:-
1.Principle of forced air seed drying.
2.Properties of air and their effect on seed drying.2.Properties of air and their effect on seed drying.
3.Moisture equilibrium between seed and air.
4.Psychrometric chart and its use in measuring
properties of air.
5.Direction of air flow and terms used to measure
rate.
6.How drying proceeds in the seed.

7. 1.Principle of forced air seed drying.
• Seeds is a hygroscopic living material.
• Its moisture content depends upon.
• 1.Temperature & RH of outer air.
• 2.Water vapour inside seed and air.
• Seed drying take place when there is a net
movement of water from seed into air.movement of water from seed into air.
• The rate of moisture migration depends upon
temp. of seed, physical structure, chemical
composition of seed and seed coat
permeability.

8. 2.Properties of air and their effect on seed drying.
• Relative humidity:- it is used to decide of air
application viz. dry air or heated air
• Dry and wet bulb temperature: Determined by
sling psychrometer by the dry and wet bulb
temperature of the air at any given temp. The
wet temp gives the relative humidity of the airwet temp gives the relative humidity of the air
by using the Psychrometric chart.
• When forced air goes through seed its temp.
lowered and RH incresed. When its saturated
fully no drying happens

9. • The initial temp. of Dry air when it is not
saturated is called dry bulb temp. and the
final temp. at which air is fully saturated is
called wet bulb temp.
• Td = Dry bulb temp. Tw = wet bulb temp.
• Td - Tw = wet bulb depression.• Td - Tw = wet bulb depression.
• For practical purpose sling psychrometer is kept on the air
stream entering on a dry bin and then wet bulb depression
is calculated.
• Generally 4400 pound degrees F of air is required to
evaporate one pound of water

10. • The following formula calculates the amount
(pounds) of air for water evapouration.
• Q=4400 / Td-Tw
• Eg : Td = 25 degree celcius Tw = 20 degree celcius
• Wet bulb depression Td-Tw = 5• Wet bulb depression Td-Tw = 5
• Q = 4400 / 5 = 880 pounds degree F of air is
required to evaporate one pound of air
• Dew point: It is the temp. at which RH of the
air is increased to 100 %

12. 3.Moisture equilibrium between seed and air.
• A certain level of seed moisture content
where seed neither take up moisture nor
release the moisture at any given temp.
However the drying air is not saturated
• Eg: Seeds at 14 % MC no drying is possible
when air temp. is 60 degree Farenheit and RHwhen air temp. is 60 degree Farenheit and RH
is 70 % .because seeds has some innate ability
to hold the water molecules.
• At any fixed MC of seed if temp. drops its
holding for remaining MC increases

13. • Seed air Moisture Equilibrium is a condition of
Grain % MC and RH when Moisture retaining
Capacity of seed and Moisture withdrawing
tendency if air comes into ballance

28. Relative
humidity
Humidity
ratio
SPECIFIC ENTHALPY
DEW POINT
ratio
SPECIFIC Volume

33. Pound of Water content per Bu. At % MC
Amount of Water per bushel
Seed moisture Soybean Grain Sorghum Corn Oats
Wheat
Dry matter / Bu 51.6 lbs 48.2lbs 47.3lbs 27.6lbs
35 27.8 26.0 25.4 14.8
30 22.1 20.6 20.2 11.8
28 20.1 18.7 18.4 10.7
26 18.2 16.9 16.6 9.726 18.2 16.9 16.6 9.7
24 16.4 15.2 14.9 8.7
22 14.6 13.6 13.3 7.8
20 12.9 12.0 11.8 6.9
18 11.4 10.6 10.4 6.0
16 9.8 9.2 9.0 5.2
14 8.4 7.8 7.7 4.5
12 7.0 6.6 6.5 3.8
10 5.8 5.4 5.3 3.1
8 4.5 4.9 4.1 2.3

34. Recommended temp. & Depth for
drying
Seed Maximum Depth
(inch)
Recommended
Drying temp.
Shelled corn 20” 110 °F
Wheat 20” 110 °F
Barely 20” 105 °F
Oats 36” 110 °F
Rice 18” 110 °F
Soybeans 20” 110 °F
Peanuts 60” 90 °F
Grain Sorghum 20” 110 °F

35. Maximum moisture content
for safe storage
Crop Maximum moisture content for
storage %
Shelled corn 13
Wheat 12Wheat 12
Barely 13
Oats 13
Rice 12
Soybeans 11

43. Thank YouThank You