Depend on the area where the polytunnel is located. We always recommend to grow the plants, have good market value and giving high and quality yield under a controlled environment.
There are many hot arguments on this, but Its recommend to position along the East -West direction in a tropical country like Sri Lanka.
Ideally you should position your polytunnel so it gets maximum exposure to sunlight. If you’re in an area which suffers from high winds it would be wise to choose as sheltered a location.
Normally, in high wind areas, polytunnel frame is properly anchored to the ground using Anchor Plates, Base Rails, Crop Bars, Triple Ridges, and P Clips.
There is no best size, but there are different extent of polytunnels in Sri Lanka with 1000 sq. ft – 5000 sq.ft, depending on the available space. Normally 1000 sq.ft. occupies less than 5 perch area.
Cost depends on the size and adding features such as automatic supply of water and fertilizer, controlling high temperature with mister and exhaust ducting system, solar powered or not, and also construct with high quality (25 x 40 mesh) insect proof mesh, UV treated diffused poly-film (5 layered)., higher gauge galvanized..etc.
Misters and or exhaust fans with ducting system can be used. If it controls with IoT sensors it would be very convenient.
Theoretically there should be no any pest attack in polytunnels but, in some cases, thrips and mites attacks maybe occurred. Yellow sticky traps are suitable to attract whiteflies, aphids, moths, leafhoppers and leafminers, while blue sticky traps are more effective against thrips.
Spraying of sulfur solution. If the disease further spreads, recommended insecticides can be used. For further details contact your Provincial Department of Agriculture.