Growing crops out of season in controlled atmosphere inside polythene tunnel is referred to as off-season technology or tunnel farming. In Pakistan, this kind of farming is normally adopted for off-season cultivation of summer vegetables. As it is not possible to grow summer vegetables in open field from December to February due to low temperature and high frost conditions. In this technology artificial heat is generated within system as sunlight passes through plastic polythene.
For tunnel farming sandy loamy soil with a good drainage system is desirable. The soil must be rich in organic matter with at least 5-10 percent organic content and PH of the soil must be in a range of 6-7. The tunnel should be located near road side. Any shadow occurrence due planation must be avoided. Availability of fresh water for the irrigation purpose must be ensured. The structure should be protected from animals and should be monitored properly and the direction of the tunnel should be toward north south.
The tunnel structure depends mostly on the financial status of farmer. However, the inverted “U” and “V” shaped tunnels are mostly common. Because in this type of tunnels, the damage due to speedy winds and rainfall is minimized. By using high tunnel technology many off-season vegetables like tomatoes, cucumber, brinjal, hot pepper, sweet peppers and fruit like watermelon, melon and strawberry can be cultivated.