Protected cultivation

In the present scenario of perpetual demand for better quality vegetables and continuously shrinking land holdings, protected cultivation is the best choice for quality produce and efficient use of land and other resources. Protected cultivation means some level of control over plant microclimate to alleviate one or more of abiotic stresses for optimum plant growth which can be achieved in naturally ventilated poly-house or net-/polynet-house. Crop yields can be several times higher than those under open field conditions, quality of produce is superior, higher input use efficiencies are achieved and vegetable export can be enhanced. Extreme weather conditions, in some countries, under the open field conditions are the major limiting factors for achieving higher yield and better quality of vegetables. Under such circumstances, protected cultivation is best option. Keeping these points in view, net-house and naturally ventilated poly-house technology has been recommended for the cultivation of different vegetables.

Modified design of net-house - polynet-house

Polynet-house is a framed structure consisting of GI pipes covered with ultra violet (UV) stabilized plastic film of 200-micron thickness at the top and UV stabilized net of 40-mesh size on the sides. A relatively cost effective and stable structure of poly net house has been designed and different pipe sizes to be used for its construction.

Selection of site

• The site for the net house should be well drained and fairly shadow free.
• It should be away from the obstruction at least three times the height of the obstruction.
• Windbreaks are desirable and at least 30 m away on all sides to minimize the adverse effect of wind.

Orientation

Polynet-house should be constructed in the east–west direction to get the maximum benefit of the sunlight throughout the year and to minimize the adverse effect of wind. The detailed dimensions for its construction are given in table 1.