2017 ASHS Annual Conference

High tunnels are proven profitable season extension tools for specialty crop farmers. This low-tech, low-cost structure with one layer of polyplastic film will advance one hardiness zone in the Midwest and extend the growing season for about four to six weeks. In the Southeast (cold hardiness zone 7&8), our research indicated that the cold hardiness zone would be advanced by 1-1.5 hardiness zones when row covers were applied for frost protection. The number of frost free days was extended by at least six weeks, when compared to that in the open field. The grow degree days (GDD) at 10ºC was increased by more than 110% from November to February, and by 100% at 4.4ºC. Soil temperature under black plastic mulch remained above 5ºC throughout the winter. Without prompt ventilation, air temperatures inside a high tunnel could easily reach over 38ºC in deep winter on sunny days. Including low tunnels in a high tunnel greatly increased the number of GDD and soil temperatures, however, the low temperatures in low tunnels were actually lower than that without low tunnels. The addition of low tunnels did not mitigate freezing damage to strawberry fruit and open blossoms. The characteristics of high tunnel/low tunnel microclimate would provide the baseline information on management strategies for high tunnel crops. Temperature managements strategies for high tunnel cool and warm season vegetables, and strawberries will be discussed.