Poly Farming , a Modern Technique to Revolutionize the Traditional Farming Techniques

poly-farming

In the recent years poly-farming has become a trend in traditional farming. Poly-farming have many advantages over traditional farming.It enables a farmers to grow vegetables and fruits throughout the year of different varieties irrespective of the soil or weather conditions.

But what exactly is poly farming is and how often is it related to open field farming?

A Poly House is a Structure made of polyethylene, usually in 3 shapes Barrel Shaped,Ridges and Furrow and Saw Tooth Shaped.The interior heats up because incoming solar radiation from the sun warms plants, soil, and other things inside 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 Poly House. Poly house farming.Poly Houses can be used to provide a higher temperature and/or 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 Flowers and vegetables to be grown at times usually considered off season. Every factor influencing a crop can be controlled in a Poly House.Poly Houses are mainly used in temperate regions in similar ways to greenhouses and cloches (row covers). Modern designs allow sowing and harvesting machines to move inside the structures so as to automate production.Poly Houses can be used by farmers to promote the cultivation of vegetables both on-season and off-season, and would actually help to moderate the market rate for vegetables and flowers in long run, on a year-round basis, and would help to satisfy local market needs.

Poly-farming is a technique of growing vegetables and fruits in a controlled environment,which is scientifically designed just like a plant needs to grow.In a poly house similar conditions are made to make a crop grow in a large structure.Greenhouses are constructed to provide the necessary light and darkness .

In poly-farming many varieties of vegetables can be grown like the colored capsicum and colored tomatoes along with various varieties of berries and Pepper.Efforts are made by Indian government to provide upto 40 percent of subsidy on poly-farming equipment(s) , which mainly include sheets and pipes to straighten the green house .

Aspects of Greenhouse Cultivation

The design and specification of a poly house is based on the following aspects:

I. Classification of Greenhouse

II. Design and Orientation of Greenhouse / Poly-house

III. Components of Green House

Classification of Greenhouse based on Suitability

a .Low Cost or Low Tech Greenhouse

A Low cost greenhouse is a simple structure constructed with locally available materials such as bamboo, timber etc.An ultra violet (UV) film is used for cladding materials. Unlike conventional or hi- tech greenhouses, no specific control devices 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 shady materials like nets.Temperature can be maintained in summers by opening the side walls. Such a structure is used as rain shelter for crop cultivation.This type of greenhouse is mainly suitable for a cold climatic zone.

b. Medium-Tech Greenhouse

Greenhouse users prefer to have a manual or semiautomatic control arrangement in order to save money.This type of greenhouse is constructed using galvanized iron (G.I) pipes. The canopy cover of such a greenhouse is attached to a structure with the help of screws. The whole structure is firmly fixed to the ground to withstand all disturbances against wind. Exhaust fans with thermostat are provided to control temperatures. Cooling pads for evaporation and misting arrangements are also made to maintain a favorable humidity inside the greenhouse.As these systems are semi- automatic, they, require lot of attention and care.It is very difficult and cumbersome to maintain a 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 environment parameters are fully automatic in nature

Classification of Greenhouse based on Cost of Poly-houses

a. Less expensive greenhouse without fan and pad 
b. Medium cost greenhouse with natural ventilation without fan and pad system
c. Expensive greenhouses with fully automatic control system
The design of a greenhouse should be based upon sound scientific principles which
facilitates controlled environment for the plant growth. Controlled environment plant production systems are used widely throughout the world to produce plant materials and products at a particular time or place, or of a quality that cannot
be obtained outdoors.Controlled environment agriculture requires far more capital investment per unit area than field agriculture and thus must essentially be correspondingly more intensive to justify its investment costs. A greenhouse is a structure covered with transparent material in order to allow natural light for plant growth. The main components of greenhouse like structure, covering/glazing and temperature control systems need proper design for healthy growth of plants.
Under Indian conditions, Quonset type , Multispan greenhouse is most suitable, because of its low cost and eases of fabrication.An Ultra violet resistant low density polyethylene (UVLDPE) single film cladding of 200 micron thickness is sufficient for Naturally Ventilated (NV) greenhouse along with fan and pad (FP) greenhouses. This should be fully tightened by stretching on the structure to avoid flute rand tearing. It should not be nailed or screwed to the enclosed structure as has a chance of tearing.

Design of a Greenhouse for Poly-Farming

The structure has to carry the following loads and is to be designed accordingly:
a)Dead Load: Weight of all permanent construction, cladding, heating and cooling equipment,water pipes and all fixed service equipments to the frame.
b)Live load: Weights superimposed by use (includes hanging baskets, shelves and
persons working on roof). A greenhouse has to be designed for a maximum of 15 kg
per square meter live load. Each member of roof should be capable of supporting 45 kg
of concentrated load when applied at its centre.
c)Wind Load: The structure should be able to withstand winds of 110 Km/hr and wind pressure.
d)Snow load: These are to be taken as per the average snowfall of the location.The
greenhouse should be able to take dead load plus live load or dead load plus wind
load plus half the live load.
The greenhouses are to be fabricated out of Galvanized Iron Pipes. Its foundation can be
60cmx60cmx60cm or 30 cm diameter and one meter depth in PCC of 1:4:8 ratio. The vertical poles should also be covered up to a height of 60 cm by PCC with a thickness of 5cm. This avoids the rusting of the pole.

Components of a Greenhouse

1. Roof : Transparent Cover of a Green House.
2. Gable: Transparent Wall of a Green House
3. Cladding Material: Transparent Material mounted on the walls and roof of a Green
House.

4. Rigid Cladding Material: Cladding material with high degree of rigidity because any deformation of the structure may result in damage to it. Ex. Glass

5. Flexible Cladding Material: Cladding material with low a degree of flexibility because deformation of the structure will not result in any damage to it. Ex. Plastic film
6. Gutter: Collects and Drains Rain Water and Snow which is place at an elevated level between two spans.
7. Column: Vertical Structure carrying the green house structure
8. Purlin: a member who connects cladding supporting bars to the columns
9. Ridge: highest horizontal section in top of the roof
10. Girder: horizontal structure member, connecting columns on gutter height
11. Bracings: To support the structure against wind
12. Arches: Member supporting covering materials
13. Foundation pipe: Connection between the structure and ground
14. Span width: Center to center distance of the gutters in multispan houses
15. Green house length: dimension of the green house in the direction of gable
16. Green house width: dimension of the green house in the direction of the gutter .

Comparison of Different Kinds of Covering Materials used in Poly-farming

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