Dr. (Mrs.) Anamika Sharma ICAR Research Complex for NEH Region Nagaland Centre Poly house or plastic house is a greenhouse covered with polythene sheet. Being light in weight, easy to handle, resistant to hail and cheaper in cost, the polythene is now most preferred material for covering a greenhouse. The poly house cultivation is possibly the most intensive method of crop production. It is highly productive and protective of environment. Since vegetables are treated as high value crops and their regular supply in the market in fresh condition is an essentiality, the utility of poly house has been found to be maximum with respect to these crops. Depending upon the surface area to be covered, prevalent weather conditions, availability of the construction material, flexibility required, cost and the aesthetic appearance, shape and style of a poly house may be chosen. For small farmers’ single span greenhouse are good, but for a large-scale commercial production of a single crop or more crops requiring similar growing environment, gutter connected multispan greenhouses are economical. Woods, bamboo, GI pipe, angle iron, and aluminum are common materials used for the frame work of a poly house. Durability of the structure depends on the type of materials used. Ultraviolet treated transparent plastic film of 150-200micron thickness is commonly used covering material. Such films have 4-5 years life. For efficient round the year utilization of a poly house, some seasonal control is exerted over the environmental factors like air, light, temperature and humidity. Low-cost poly house In low -cost poly house, no equipment is installed to control the environment artificially. In subtropics during winters poly house is kept completely closed in night, while in day times, depending upon the light intensity, doors and / or windows are kept open to allow ventilation. Depending upon ventilation, the temperature in side the poly house is 50-120 C higher than outside air temperature. During summer, over heating of the poly house is a problem which could be avoided by opening the side walls also in addition to doors and windows. Besides use of shading nets and frequent watering are also helpful. Medium-cost poly house In medium cost poly house, sidewalls are need not to be flexible. Usually fan-pad cooling system is adopted during summer to keep a check over the temperature rise, besides using shading nets and applying frequent watering through micro-sprinkler. During winter, hot air blowers may be used to maintain higher temperature. High-cost poly house In high-cost poly house, there is complete control over the environment. For uniform heating, usually propane or electric heater is used. The heat generated is passed through perforated tubing. Heating may also be done by circulating hot water/steam through pipes. Irrigation is applied through micro-sprinkler /micro-sprayer / drip irrigation system. All the operations in high-cost poly greenhouse may be controlled and fully automated. The poly house cultivation is beneficial only when off season vegetables are grown. It is useful in production of vegetable nursery under adverse weather conditions. The choice of crops depends upon the size of poly house structure, market demand as well as expected market price. While it is convenient to raise any vegetable crop in environmentally- controlled poly house during any part of the year, the selection of crops are more critical in case of ordinary low- cost poly houses. In subtropics, cucumber, bottle gourd, capsicum and tomato give quite remunerative yields during winter in low cost poly houses. With proper ventilation cabbage, early varieties of tropical cauliflower and coriander can be successfully grown during summer/ rainy season. It is well established that if seeds of cucurbits are sown in small plastic bags during winter and the seedlings are reared in poly house, they remain safe from injury and become ready for transplanting early in February to give early and remunerative harvest.