Growing out-of- season crops in controlled atmosphere inside polythene tunnels is called 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 vegetable in open fields from December to February due to low temperature and high frost levels, so these are grown inside polythene tunnels so that proper atmosphere may be given to plants for their maximum growth and yield. Because of controlled atmosphere, Tunnel farming is the source of higher yields and earlier production, and this earlier and quality produce gives good profits to farmers. For this reason, modern and progressive farmers of Pakistan are adopting this advance mode of farming at a faster pace.
Weather remains moderate in province of Sindh, so we get summer early crops in this province. But in Punjab and other areas of Pakistan, Tunnel farming is the only way to get off-season production of summer vegetables. Tunnel farming involves constructing tunnels like Greenhouses i.e. hut-like structures swathed in plastic that serve as cocoons for growing cucumber, tomato, pepper, carrot and lettuce etc. In addition to summer vegetables, production of strawberry inside tunnels has also become very popular in the recent years.
The idea of tunnel farming is to shield the crops from the elements and trap the heat of the sun, extending the growing season and increasing production. Tunnel farming is gaining acceptance among educated farmers as it provides them with an opportunity to save the input resources by using less than 40 per cent water, fertilizer and other resources under controlled conditions. Through tunnel farming, it is possible to overcome the three main impediments that impact agricultural growth: chronic water shortages, low yield per acre and low value of crop production.
Tunnel farming operates on the principle that of creating conditions during winter that are equivalent to those in summers. The vegetables sown in summer are then cultivated in these tunnels during winter. The entire farming area is covered by transparent polythene sheath fixed over D-shaped Bamboo/steel/aluminum pipes. The soil/growing media is also covered with black colored polythene sheath with small holes in which the seeds are sown. The sunlight during the day passes through transparent polythene sheath and is absorbed by the black sheath spread over the soil/growing media. This raises the temperature to desired level inside the tunnel. The plastic sheet on the soil serves three purposes: i) First it traps heat, ii) it reduces water loss and iii) it eliminates growth of weeds enormously.
Types of Tunnels:
High tunnels give maximum yield of crops and make easy soil preparation, picking, spraying due to its width and height. The tunnel is suitable for growing tomatoes, cucumbers and sweet peppers.
These are lower in height as compared to High tunnels. Walk-in-tunnels provide high yield compared to Low tunnels. The tunnel is suitable for growing tomatoes, cucumbers, sweet pepper and hot pepper.
Low tunnels are less expensive as compared to the High tunnels but crop yield is low. Soil preparation, spraying and picking is difficult in this type of tunnel. Cucumber, melons, watermelons, bitter gourds, squashes, and snake gourds etc. can be grown in this type of tunnels.
Things to remember before start:
- Prior to start off-season vegetable cultivation in tunnels, the investor must have practical knowledge about farming.
- Soil and water quality of the farming site should be tested before start.
- Self-pollinated plants should be grown.
- Recommended seed should be used.
- Farmer must have complied and critically analyzed market information to earn high profits.
- To introduce intensive cultivation per unit area.
- To get maximum output/unit area.
- To get production as per market demand.
- To minimize the environmental Hazards.
- To increase the life span and production ability of the plants.
- To promote vertical cultivation to enhance quality and quantity of the produce and to lessen the area availability issues.
- To get 3-5 times more production as compared to that taken in an open field.
- To fetch higher price of produce because of its early availability in the market.
- To save the input resources like water, fertilizer and Time & space.
- To manage the crops in controlled and comparatively easy conditions.
- To grow the crops in shorter time periods/growing seasons.
Suggestions for Successful production:
- Always keep the direction of the tunnel from East to West for better temperature gains inside the tunnel.
- Always use good quality seed.
- For cucumber, use Parthinocarpic variety seed.
- For tomato, use indeterminate variety seed.
- Use fertile soil and maintain its fertility during throughout the season.
- Always grow more profitable vegetables as per market survey.
- Protect seed of cucumber from rodents and insects till its germination.
- Irrigate in morning and evening or as per expert’s advice according to the growing/atmospheric conditions inside your tunnel farm.
- All plants are tied up with rope.
- Prune the plants particularly three nodes at initial stage.
- Use minimum quantity of farm yard manure for cucumber as compared to sweet pepper and tomato crops.
- Use drip irrigation for economic irrigation and fertilizer application.
- To avoid germination of weed, use black mulch into the growing bed.
- Apply proper pesticide at proper time to control the insects or fungi.
- Smoking is strictly prohibited inside Tunnel as it may cause a quick spread viral diseases throughout the tunnel.
Temperature requirements for Best Growth of Vegetables:
Growing season for Off-season production of selected vegetables: