Horticulture :: Greenhouse cultivation

1. Designs and classification of greenhouse
2. Orientation Of Greenhouse / Polyhouse
3. Components of green house
4. Plant growing structures/containers in green house production
5. Environmental factors influencing greenhouse cultivation
6. Media preparation and fumigation
7. Drip irrigation and fertigation systems greenhouse cultivation
8. Cost estimation for green/polyhouse construction
9. Problem management in greenhouse cultivation
10. Special horticultural practices in greenhouse production
11. Physiological disorders of greenhouse grown cut flowers
12. Post harvest handling practices for cut flowers

 Carnation under low cost greenhouse

1. Designs and classification of greenhouse

Greenhouses are frames of inflated structure covered with a transparent material in which crops are grown under controlled environment conditions. Greenhouse cultivation as well as other modes of controlled environment cultivation have been evolved to create favorable micro-climates, which favours the crop production could be possible all through the year or part of the year as required. Greenhouses and other technologies for controlled environment plant production are associated with the off-season production of ornamentals and foods of high value in cold climate areas where outdoor production is not possible. The primary environmental parameter traditionally controlled is temperature, usually providing heat to overcome extreme cold conditions. However, environmental control can also include cooling to mitigate excessive temperatures, light control either shading or adding supplemental light, carbon dioxide levels, relative humidity, water, plant nutrients and pest control.

Classification of greenhouse based on suitability and cost
a) Low cost or low tech greenhouse
Low cost greenhouse is a simple structure constructed with locally available materials such as bamboo, timber etc. The ultra violet (UV) film is used as cladding materials. Unlike conventional or hi-tech greenhouses, no specific control device for regulating environmental parameters inside the greenhouse are provided. Simple techniques are, however, adopted for increasing or decreasing the temperature and humidity. Even light intensity can be reduced by incorporating shading materials like nets. The temperature can be reduced during summer by opening the side walls. Such structure is used as rain shelter for crop cultivation. Otherwise, inside temperature is increased when all sidewalls are covered with plastic film. This type of greenhouse is mainly suitable for cold climatic zone.


b) Medium-tech greenhouse
Greenhouse users prefers to have manually or semiautomatic control arrangement owing to minimum investment. This type of greenhouse is constructed using galvanized iron (G.I) pipes. The canopy cover is attached with structure with the help of screws. Whole structure is firmly fixed with the ground to withstand the disturbance against wind. Exhaust fans with thermostat are provided to control the temperature. Evaporative cooling pads and misting arrangements are also made to maintain a favourable humidity inside the greenhouse. As these system are semi-automatic, hence, require a lot of attention and care, and it is very difficult and cumbersome to maintain uniform environment throughout the cropping period. These greenhouses are suitable for dry and composite climatic zones.

c) Hi-tech greenhouse
To overcome some of the difficulties in medium-tech greenhouse, a hi-tech greenhouse where the entire device, controlling the environment parameters, are supported to function automatically.

Cost involved
1.     Less expensive greenhouse without fan and pad          Rs.300 to 500/m2

2.     Medium cost greenhouse with pad and fan system       Rs.800 to Rs.1100/m2
        without automation                                                       

3.     Expensive greenhouses with fully automatic                Rs.2000 to Rs.3500/m2
        control system                

Other classifications
The greenhouse can also be classified based on type of structures, type of glazing, number of spans, environmental control etc. The various types are as follows.

Classification as per type of structure
a. Quonset type
b. Curved roof type
c. Gable roof type

Classification as per glazing
a. Glass glazing
b. Fiberglass reinforced plastic glazing
i. Plain sheet
ii. Corrugated sheet
c. Plastic film
i. Ultra violet stabilized low density poly ethylene
ii. Silpaulin

Classification based on number of spans
a. Free standing or single span
b. Multispan or ridge and furrow or gutter connected

Classification based on environmental control
a. Naturally