polyhouse, hot bed and humidifier in horticulture is used in protected cultivation

3. DEFINITION
 One method of raising vegetable seedlings even in
cold weather is called the Hot Bed
 The hot bed is a way or providing extra heat to the
soil and growing seedlings in the cold season, so
seedlings can be grown ahead of time. This means
that vegetables can be grown off season, even in cold
climates

4. MAKING
 Choose a good site for the nursery. This must be easy
to protect and maintain, with plenty of sun
 Dig a trench. The trench should be 1 metre wide,
50cm deep, and as long as you need for the amount
of plants to be grown
 Place a 3 inch thick layer of straw or leaf litter in the
bottom of the trench

5.  On top of this place a 3 inch layer of raw, fresh cow
or horse dung, and wet well
 On top of the dung place another 3 inch layer of
straw or leaf litter
 Then return a 3 inch layer of the soil dug from the
trench
 Finally put a 3 inch layer of fine, fertile soil (which
can be made by mixing compost with the dug out
soil)

6.  The seed will be sown into this layer of fine, fertile
soil
 In the Hot Bed we can sow seeds direct into the soil,
or into leaf pots filled with the same soil. After
sowing the seed, cover the bed with a thin layer of
finely chopped mulch
 Finally, the bed is covered with a sheet of plastic.
First of all make a bamboo frame on which to hang
the plastic
 Bury the edges of the plastic in the soil around the
bed, so air cannot get in

7. 1. Heat from the dung helps
seeds to germinate
2. The plastic helps to protect
growing seedlings from frost
plastic
thin
mulch
heat
hea
t
see
dsoil+ compost
soil straw
cow dung
50cm
sun sun
seedling
plastic

8. HEATING SYSTEMS
 Pit hot bed
 Fuel-heated hot bed
 Electric hot bed
 Steam/hot-water hot bed

9. MAINTENANCE
• When the sun is out the plastic can be folded back to
irrigate and weed the nursery as required
•Replace the plastic in the evening, when the sun goes
down
• Heat from the dung warms the soil, and the plastic
prevents it quickly escaping
• When the danger of frost has passed the seedlings in
the hot bed can be transplanted into the kitchen
garden

10. Species to growin the hot bed
Season/Planting
method
Leaf pots
Direct into the
bed
Rainy season
plants
Cucumber,
gourds, beans,
etc.
Chillis,
aubergine,
ladies‘ finger,
sunflower, etc.
Dry season
plants
Beans, peas,
etc.
Tomatoes,
broadleaf
mustard,
chard, lettuce,
onion,
cabbage, etc.

11. ROLES
 In cold climates and at high altitudes, for several months
over Winter and early Spring there is snow and frost,
which prevents seeds germinating and can kill young
plants. For this reason seedlings can't be grown until the
time for frost has past and the weather warms up. By
making a hot bed, seedlings can be grown even in the
winter
 This means that vegetables can be produced 1 or 2
months earlier than usual. There are also economic
benefits from this. If vegetables can be raised off season,
i.e. ahead of time, they can be sent earlier to the market
when prices will be higher

12. POLYHOUSE

13. DEFINITION
 A polyhouse is a tunnel made of polyethylene, usually
semi-circular, square or elongated in shape
 The interior heats up because incoming solar
radiation from the sun warms plants, soil, and other
things inside the building faster than heat can escape the
structure
 Air warmed by the heat from hot interior surfaces is
retained in the building by the roof and wall
 Temperature, humidity and ventilation can be controlled
by equipment fixed in the polytunnel

14. CONSTRUCTION
 The poly-houses are constructed with the help of
ultraviolet plastic sheets, which last for more than
five years
 The basic structure is prepared with bamboos or iron
pipes. Iron pipe structure is costly but durable than
bamboo
 The structure is covered with 1501-micron thick
plastic sheet
 Generally the length of the polyhouse is 25-30 feet
and width 4-5 feet
 The direction of the poly-house is always East to
West, so that the maximum sunshine is available
 The house should not be constructed in shade

15. METHOD OF HEATING
Heating is required in the winter season. Generally the
solar energy is sufficient to maintain inner temperature of
poly-house but some times a micro temperature is
required to be supplied to some crops. For this a few
methods may be followed:
i) Constructing a tunnel below the earth of the poly-house
ii) Covering the northern wall of the house by jute clothing
iii) Covering the entire poly-house with jute cloth during
night
iv) Fitting a solar energy driven device in the poly-house

17. METHOD OF COOLING
In summer season when the ambient temperature rises
above 40°C during day time, cooling of poly-house is
required, which may be achieved by the following
methods:
i) Removing the internal air of the polyhouse
ii) Sucking external air by putting a fan on
iii) Installation of coolers on eastern or western wall not
only keeps temperature low but maintains proper
humidity also
iv) The temperature of the poly-house can be controlled

18. TECHNIQUE
 The Crops can be grown in pots or in the soil
 Before sowing the seeds, rotten manure is filled in polythene bags
of 10 x15 cm size, along with equal quantity of soil and sand
 Water is sprinkled on the bags and seeds are sown in the bags
 Small holes are formed in the bags for easy aeration
 These bags are kept inside the poly-house till the plants grow to
about 10-15 centimeters and are then transferred to pots or earth
 These plants should be given manure and water from time to time
 Generally disease does not spread, if at all, a little spray may be
required
 For earning maximum profit through maximum production from the
crops grown in the poly-house, their cleanliness and pruning is also
very important
 Luxuriantly growing tomato crop requires sticking or otherwise
their plants will fall on the ground and get spoiled

19. USES
 Polytunnels can be used to provide a higher
temperature/humidity than that which is available in the
environment but can also protect crops from intense heat,
bright sunlight, strong winds, hailstones and cold waves.
 This allows fruits and vegetables to be grown at times
usually considered off season. Every factor influencing a
crop can be controlled in a polytunnel
 Polytunnels are often used in floriculture and nurseries as
the economic value of flowers can justify their expense

20. TEMPERATEREGIONS
 Polytunnels are mainly used in temperate regions
 Modern designs allow sowing and harvesting
machines to move inside the structures so as to
automate production
 Polytunnels have had a significant effect on the
production of strawberries in the United Kingdom
 Other soft fruits such
as raspberries and blackberries are also cultivated in
the same way

21. TROPICALREGIONS
 In a tropical climate, temperatures are prone to soar
above all normal levels
 In such cases, foggers/misters are used to reduce the
temperature
 This does not increase the humidity levels in the poly
house as the evaporated droplets are almost
immediately ventilated

22. EXAMPLE  For example, in India, the
inability to grow tomatoes
generates price spikes
during the monsoon season
 This is seen as an ideal
time to grow tomatoes in
polytunnels, since they
providing the ideal climate
for the crop
 In India, the Abhinav
Farmers Club grows
flowers and organic
vegetables in polytunnels

24. IMPORTANCE
 Plants can't live without water & most plants
are mostly composed out of water and the well-
being of a plant, depends on the relative humidity of
its surroundings
 Leaves lose water through evaporation through their
stomata – small openings in special cells on the leaf
surface where gaseous exchange takes place if
the relative humidity is too low, a plant will start to
give up some of its water into the surrounding air
which will result in the plant drying out and wilting

25. OBJECTIVES
 Eliminating the application of excess water
 Soaking and cooling of the propagation medium
 Temperature and humidity control reduces the stress
on cuttings which occurs during intervals of high
temperature or low humidity
 Needed only during daylight hours and are unusual
hot night winds

26. REQUIRES THE CONSIDERATION OF FOUR FACTORS
 Ambient air temperature
and relative humidity
 Humidification rate of
incoming air
 Rate of air exchange
 Air exchange between
cuttings

27. OPERATION
 Cuttings are maintained under controlled temperature and
humidity
 Temperature is maintained at a determined point by
controlling the amount of solar heated air that is exhausted
 Humidity is maintained as close to hundred percent as
possible by humidifying all incoming air
 Misting by directly humidifying the air around the cutting
 50- 70% shading reduces the amount of heat generated during
the summer season to manageable levels and still allows
ample light for the cuttings
 The minimum amount of light needed for propagation but
reduction of rooting has not been observed with as much as
80% shading

28. REFERENCES
 https://en.wikipedia.org/wiki/Polytunnel
 https://hort.purdue.edu/ext/HO-053.pdf
 http://www.jaybird-
mfg.com/applications/horticulture/aquafog-and-
propagation/
◦ Aquafog and Propagation by Daniel C. Milbocker