Saturday, January 1, 2011

Polyhouse

Construction of a Polyhouse

The polyhouses are constructed with the help of ultraviolet plastic sheets, so that they may last for more than 5 years. The structure is covered with 1501 m thick plastic sheet. The structure is prepared with the bamboos or iron pipes. Iron pipe structure is costly but more durable than bamboo.

Generally the length of the polyhouse is 25-30 feet and width 4-5 feet. The direction of polyhouse is always East to West, so that the maximum sunshine is available. The house should not be constructed in shade. The size of polyhouse may differ depending on the necessity. The polyhouses are kept cold or hot depending upon the season.

Use of Polyhouses:

From the point of view of earning more profit only such off-season crops should be grown, which are being sold at higher prices in the market. Big hotels in cities are mostly in the need of off-season vegetables and so is the case with some prosperous people in big cities. In such areas and also in the hill and remote regions where fresh vegetables are required regularly for meeting out the requirements of security forces, the construction of polyhouses is more lucrative and is a must.

The crops grown under the polyhouse are safe from unfavourable environment and hailstorm, heavy rains or scorching sunshine, etc. Crops of the polyhouse can be saved from birds and other wild animals. The humidity of polyhouse is not adversely affected by evaporation resulting in less requirement of water. In limited area of polyhouse, insects and pests control is also easy and less expensive.

By adopting the modern technology of polyhouse, the difference in the demand and supply of off-season vegetables and fruits etc. can be minimised. This facilitates in maintaining the quality of the product also.

Heating of Polyhouse

Heating is required in winter season. Generally, the solar energy is sufficient to maintain inner temperature of polyhouse but some times more temperature is required to be supplied to some crops. For this few methods are as follows:

Constructing a tunnel below the earth of poly house.
Covering the northern wall of the house by jute clothing.
Covering whole of the polyhouse with jute cloth during night
Fitting solar energy driven device in polyhouse.

Cooling of Polyhouse

In summer season, when ambient temperature rises above 400C during day time the cooling of polyhouse is required by the following measures, not only the temperature but also relative humidity of polyhouse can also be kept within limit.

Removing the internal air or polyhouse out of it in a natural manner.
Changing the internal air into external air by putting the fan on.
Installation of cooler on eastern or Western Wall not only keeps temperature low but maintains proper humidity also.

Running water-misting machine can control the temperature of the polyhouse.

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