A polytunnel (also known as a polyhouse, hoop greenhouse or hoophouse, or high tunnel) 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.
Polytunnels 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 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.
Polytunnels 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. 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.
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 enhance the humidity levels in the poly house as the evaporated droplets are almost immediately ventilated to open air.
High tech poly houses even have heating systems as well as soil heating systems to purify the soil of unwanted viruses, bacteria etc.The recent Indo-Israel collaboration at Gharunda, near Karnal is an excellent example of Polyhouse farming taking place in a developing country. If the developing countries try and develop a special program only for the farmers especially in countries like India the migration rate of the rural population to urban areas and the migration of farmers from agri/horticulture to urban areas may be reduced.This has a huge potential to improve the farming sector which has so far proved to be the vitally important sector for any country to stabilise the economy. The projects with small polytunnels used by each farmer in each village promoting cultivation of vegetables for on season and off season would actually help to develop the practise of moderating the market rate for the vegetable in long run round the year and would eventually help cultivate at least for the needsof the nearest market thus stabilising the market rates. In India, the inability to grow tomato during rainy season allows its price to soar during the monsoon. This is spotted as an ideal time to grow tomato in polytunnels providing the ideal climate for the crop. In India, Abhinav Farmers Club grows flowers and organic vegetables in polytunnels.
Exporting hoop houses from Canada to Nepal
To promote Canadian agricultural section exportation and commercial relationship with Nepal, selecting a suitable product to export is the key. By exporting cheap hoop houses, Nepalese farmers can have a higher income by having better quality and larger yield of their commercial fruits and crops. Canada, on the other hand, can have increasing number of employment. Therefore, it is a good bidirectional exportation product.
Hoop house, also named polytunnel, is an agricultural product. It has a structure composed by large hoops, pipes (metal, plastic or wood pipes) and huge plastic sheet. The baseboards are connected with tensioned skin by wood bars, metal pieces, and other materials. The advantage of hoop house is that it is cheaper than greenhouses and easier to manipulate. For expensive product is not suitable for Nepalese farmers, the hoop houses introduced here are cheap and movable ones. Customers could build and dismantle the product as they want. Hoop houses can be used to protect against unexpected weather in an effective and economical way. They can also increase the temperature maximum 10 degree without any other equipment. Price of the low cost hoop house can be varies in different sizes and materials, which has huge flexibility to transform; therefore, they can be applied on any crop at any temperature in the year.
The cost of a hoop house is around $2 to $8 per square foot in Canada, and price can have a big range depend on the type and quality of the hoop house element. The materials and price of a 12×15-square foot hoop house is shown the paper: "Integrating Hoop House Construction and Operation into an Undergraduate General Education Horticulture Class" , there are several description not part of the hoop house, so that the total price is actually cheaper than $701.20. To reach the goal of making product as cheaper as possible and easier to promote, customers can make their own unique hoop house. For instance, polycarbonate, shade cloth, row and bed covers, and polyethylene can replace the plastic in the chart. On the website of "eXtention", a non-profit learning network, Tim Coolong of the University of Kentucky introduced a season extension hoop house making tutorial, he shows audiences that low cost and movable hoop houses are customized and his hoop house only cost $0.35 per square foot. Therefore, Nepal farmers might not feel too stressful when making their own hoop houses.
Construction Method of Movable Type
The setting of a hoop house is approachable and easy. First, one need to dig trenches and place anchors at a certain distance (depend on different buyers' needs).The anchors can be regulated into the soil using a small hydraulic driven motor. Second, set up the pipes over the anchors by insert the anchor into the pipe. Third, build the end walls with wood bars as well as construct a metal pipe across all the plastic pipes and hold them up by using aluminum connectors. Next, binding the frame and plastic with ropes and finally, cover the entire frame with plastic skin and staple it.
- Bhattacharyya, Pramit (May 17, 2012). "Planting the seeds of prosperity". Livemint.com. HT Media. Retrieved November 23, 2012.
- Office of Communications: United States Department of Agriculture (USDA) (December 16, 2009). "USDA to launch high tunnel pilot study to increase availability of locally grown foods" (Press release) (Release #0617.09). Washington, DC.
- Tharp, Mike (July 17, 2009). "Once world's bread basket, Iraq now a farming basket case". McClatchyDC. The McClatchy Company.
- DeVault, George (February–March 2003). "Low-cost, versatile hoop houses". Mother Earth News.
- Hilaire, RS; Sammis, TW; Mexal, JG (April–June 2009). "Integrating hoop house construction and operation into an undergraduate general education horticulture class". HortTechnology 19 (2): 445–51.
- Coolong, Tim (February 29, 2012). "Low cost high tunnel construction". eXtension.org.