Low tunnels are ideal for the early production of many vegetable crops. They are constructed by installing 6-foot wide sheets of either slitted or perforated plastic over wire hoops that are spaced about 4 feet apart. To prevent wind damage, the cover is pulled taut over the hoops (but not stretched), and the edges are secured with soil. Generally, the cover is left over the plants for 3-4 weeks. The slits and perforations provide daytime ventilation, eliminating the need for manual venting.
Low tunnelsare generally used in conjunction with black plastic mulch for weed control and enhanced soil warming. Frost protection of 2 to 4 degrees F is afforded by the covers, but the biggest benefit is growth enhancement provided by the daily increments of solar heating. Daytime temperatures might be excessive under the cover if ambient temperatures are above 90 degrees F. Under those conditions, partial removal of the cover might be necessary, especially for tomatoes and peppers that have open blossoms.
Wire for Hoops. Number 10 gauge Smooth Galvanized Steel wire is packaged in bundles of 100. Wires are 76" long and can be inserted 6" into the soil at each end to form a support hoop that is 16" - 18" high at the center. Wires should be spaced 5' to 8' apart (see sketch below)
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