Row Covers and High Tunnels
To learn more about high tunnel technology in the Midwest go to this web site:http://www.hightunnels.org/forgrowers.htm
The objective of these season extenders is to access markets at a time when prices are at a premium. Extending the vegetable growing season with a plastic row cover was first introduced commercially fifty years ago in California . Several different row cover systems are in use with various light transmission and ventilation properties. The self-ventilating, slitted, hooped polyethylene row covers developed in the early ‘80's in New England reduced the labor requirements of hand ventilating but may cause high temperatures detrimental to early yields for some crops. This development was quickly followed in the same time period by floating row covers developed from spunbonded polyester. Next, high tunnels were introduced in the early ‘90's. They are similar to row covers in design and function, except:
High tunnels do not seem to provide more frost protection than row covers. In Iowa , a major problem with tomato has been the increased insect pressure. Also, the high cost of high tunnels requires a multiyear payback period.
The cover for a high tunnel consists of a single layer of greenhouse grade polyethylene. No artificial heating or cooling system in installed. The sides are rolled up and the end doors opened for ventilation. The main warm season vegetables grown are the high value crops as tomatoes, peppers, and melons. Some growers are looking for even more profit by production of raspberry and strawberries.
For construction considerations download a pdf file here.