Modern technology has changed how crops are grown, and tunnel technology is one of the clearest examples: vegetables raised under a controlled climate inside a polythene arch.

A semicircular frame of bamboo, iron pipe or PVC, covered with UV-resistant polythene, that shields the crop from cold, heat and rain and lets the farmer manage temperature, humidity and water.

• Site: fertile, sunny land that does not flood.
• Soil: ploughed, levelled and fertilised with organic and mineral fertiliser.
• Frame: bamboo, pipe or PVC, covered with UV-resistant film.
• Sowing: seed or seedlings at the spacing each crop needs.
• Care: regular irrigation, weeding and pest control; temperature and humidity watched inside.

Tomato, the tunnel's favourite; cucumber all year round; coloured capsicum; lettuce and broccoli for the salad trade.

• Shelter from cold, rain and heat.
• Off-season crops at off-season prices.
• 30–50 per cent more yield in the controlled environment.
• Fewer pests and diseases, and less pesticide.
• Controlled irrigation that saves water.
• Better quality, and more than one crop at a time.

Tunnel technology is not a method; it is a change in what a small field can earn.

Photo: A greenhouse at Bangladesh Agricultural University — Hermitage17 assumed (based on copyright cla / Wikimedia Commons (Public domain)