Frost Protection for Early High Tunnel Tomatoes

By extending the growing season, high tunnels increase marketing opportunities, improve early cash flow, and increase marketable yields. High tunnels make it possible to plant and crop tomatoes one month earlier than field grown tomatoes in northern Utah.   Greater protection from frost is needed if growers wish to plant more than one month earlier.  Supplemental heating can be expensive when heating a large space, but low tunnels within high tunnels trap heat around tomato plants creating a smaller volume of air to keep warm.  Sunbrite tomatoes were transplanted to four high tunnels on the Greenville Research farm in Logan, Utah over three planting dates (March 17, March 30, and April 7) in the spring of 2009.  Supplemental heat treatments included soil warming cables and 40-Watt incandescent lights (1 light for every 3 plants) which were evaluated alone and in combination for early season frost protection. Soil warming cables were buried 2.5 cm below soil and plastic mulch.  All tomato plants were grown under 2-mil plastic low tunnels measuring 0.9 meters wide and 1 meter tall.  Early yield was significantly higher in the plots heated with incandescent lights, while overall yield was similar between all heating treatments. The first three weeks of harvest were considered early.  The March 17^th planting date had significantly lower early season and overall yield, while yield was similar for later planting dates.  The difference in yield between planting dates suggests that the heating treatments in this study did not provide sufficient cold protection to prevent injury.  Information gathered in this study about costs, planting dates, and yields will be valuable to growers who want to utilize the benefits of growing tomatoes in high tunnels.