Tunnel cultivation - Tunnel Cultivation

In crop cultivation, a method of covering ridges with vinyl or poly film in a tunnel shape to keep them warm and to speed up growth or to grow safely even when the outside temperature is too low for that crop. Tunnel cultivation is mainly used for relatively short vegetables and flowers such as lettuce, spinach, Chinese cabbage, turnips, and strawberries, but it is also used for melons, cucumbers, pumpkins, watermelons, tomatoes, eggplants, etc., but these are often grown in tunnels only when they are young, so that they can continue to grow even in the low temperature period, and when the outside temperature becomes suitable for growth, they are often grown outside the tunnel for the latter half of their growth period. It is also used for raising seedlings of rice and other crops.

Tunnels are cheaper to set up than greenhouses, but the insulation effect of tunnels is less than that of vinyl greenhouses, so they are often used in warm southwestern regions where winters are relatively warm. In cold regions, they are used to supplement greenhouses, but are not suitable for areas with heavy snowfall. Also, tunnels have the advantage of suppressing transpiration and reducing the labor required for irrigation, but there are also problems with excessive moisture.

The tunnel is supported by thin rods of bamboo, plastic, or fiberglass, which are bent at right angles to the ridges and fixed in place with both ends inserted into the soil. Film is then placed over the film, which is then held down with string or rope. Both sides of the film are held down with soil, but if it gets too hot, the bottoms can be raised to regulate the temperature.

[Hoshikawa Kiyochika]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

作物の栽培において、畝(うね)をトンネル状にビニルまたはポリフィルムなどで覆って保温し、生育を早めたり、外界がその作物の生育に適さない低温の場合でも安全に栽培する方法。トンネル栽培はおもにレタス、ホウレンソウ、ハクサイ、カブ、イチゴなど比較的背丈の低い野菜や花類などに用いられ、またメロン、キュウリ、カボチャ、スイカ、トマト、ナスなどでも用いられるが、これらは若いうちだけトンネルに栽培して、低温期にも生育を進め、外界が生育に適する温度になったら、生育の後半はトンネルを除いて栽培することも多い。イネなどの育苗にも用いられる。

　トンネルはハウスに比べて設置費用が安価であるが、トンネルの保温効果はビニルハウスに比べると不完全なので、冬の比較的暖かい西南暖地で多く用いられる。寒冷地ではハウスの補助程度に用いられるが、積雪地帯には適さない。またトンネル被覆のため蒸散が抑制され灌水(かんすい)が省力される利点があるが、過湿の害もみられる。

　トンネルは竹やプラスチック、グラスファイバーの細棒を支柱にし、畝に直角に湾曲させて両端を土に挿して固定し、その上にフィルムをかけ、その上から紐(ひも)や縄をかけて押さえる。フィルムの両わきは土で押さえるが、高温の場合は裾(すそ)をあげて温度の調節を図る。

［星川清親］

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