| 摘要 |
<p>The vines are protected from the effects of frost by means of a sheet of plastic film or expanded foam. This is folded over each row to form a tunnel, its long edges meeting underneath and pinned or clipped together to enclose the main stems. Push-in joints are used for extending lengths and the complete tunnel is suspended from wires strung longitudinally above the rows. In the case of severe frost, warm air can be conveyed through the tunnels. A plastic supply duct has branch takeoffs pushed into the ends of the tunnels, circulation being by fans or natural convection.</p> |
