FOIL TUNNELS
The cultivation of horticultural plants under foil is gaining more and more supporters, because it is not complicated and speeds up the harvest of vegetables by approx 2 weeks. Currently, many structures covered with polyethylene foil are used (PE) and polyvinyl chloride film (PCW). The produced films differ in thickness and durability as well as in such practical properties, how: the degree of light transmittance, susceptibility to dirt, color and resistance to low or high temperatures. The foil with the addition of stabilizing dyes is usually light blue or light yellow in color. A slight addition of dye has no effect on plant growth, a increases the durability of the foil coating, which is still not very great in our conditions (most often it withstands only one growing season). Polyvinyl chloride foil retains heat better at night than polyethylene foil. The thickness of the foil used should depend on the type of the covered structure: thin can be used for low tunnels – thickness 0,06 mm, although slightly thicker foil has better durability – from 0,10 do 0,15 mm. Higher structures, as they are more exposed to the influence of wind and because of the longer period of keeping the cover, covered with a thick foil 0,18-0,22 mm.
The foil is produced in various widths, therefore if it is not a sleeve form (often unilaterally dissected) width 1 m, which allows you to get a belt width 2 m, it needs to be cut or connected properly. The sheets of polyethylene foil are joined by welding, using a special welding machine, or an iron with a thermoregulator set to "cotton”. This is how it is done, that a strip of thick fabric is laid on the table or plate, which is covered with cellophane tape; the edges of the foil strips are laid overlapping and the cellophane is reapplied. An iron slides over the cellophane covering the foil, pressing them down lightly; being careful, not to touch the foil directly with the hot one, for it will melt it. Instead of cellophane, you can use a more convenient and durable Teflon tape. Before starting welding, a small trial must first be carried out, that the edges are well bonded and that the foil does not melt. For better bonding, the foil is attached to a table or plate with a thin one (2 cm) and a narrow wooden slat, the width of which will correspond to the width of the weld. A strip of fabric is placed on this board.
On a plot or in a home garden, the so-called. low and semi-high tunnels and special tunnels, available in stores, small tents.
The tunnel scaffolding is usually made of bows driven into the ground on both sides of the bed. The bows can be made of vinidur tubing (bent after heating with steam), with a thick steel wire 5-8 mm, galvanized or painted with oil paint or iron tape, the so-called. cooperage, covered with a mine. The scaffolding can also be in the shape of an inspection box or the bows can be fitted to the frame. A polyethylene film of a thickness is evenly and carefully stretched over the scaffolding 0,10-0,15 mm. The long sides of the foil are covered with soil, or it captures between 2 wooden slats, or it winds evenly on the rod, which is pegged to the ground. Both outlets of the tunnel are also covered with foil.
In the case of wire construction, it is cut into sections 240 cm and in distance 20 cm from the ends of the wire bends, forming small (diameter approx. 1,5 cm) Mesh”, which facilitate the attachment of the string, holding the unfolded foil. The poles are hammered along the bed at a depth of approx 20 cm tak, to make stitches” they protruded slightly above the ground. Distance between the handles, depending on the thickness of the wire, should be 80-120 cm. The length of the tunnel can be any, while its width in this case will be 120 cm. At the beginning and end of the tunnel it positions itself, at an angle of 45 °, additional headbands, which allow the tunnel to end gently. All the headbands are connected with a string at the top, the ends of which are tied to pegs driven into the ground at the tops of the tunnel. The structure is covered with a sheet of foil 1-1,5 m longer than the structure and width 2 m. After the foil is applied, the string is threaded crosswise through the eyelets, just like lacing shoes. One of the edges of the foil is covered with soil permanently, the other, however, located on the south or west side, is intended for airing.