2017 ASHS Annual Conference

According to the Farmer’s Almanac the last spring frost and first fall frost for both Absaraka, ND and Williston, ND (east and west sides of ND) were May 15 and September 22 with 128 growing days. With this in mind, the number of vegetables crops that can be successfully grown is limited even when utilizing a high tunnel. However, in the high tunnel with the use of infrared heat strips to warm the soil and a low tunnel (frost blanket), the pepper crop was kept alive and allowed to ripen fruit even though minimum high tunnel air temperatures dropped to 19.6 and 28 °F at the Williston Irrigation Research Extension Center near Williston, ND and Horticulture Research site near Absaraka, ND, respectively. Differences between pepper cold injury under the low tunnel and the low tunnel + soil heating was more striking at Williston. A second trial evaluated container grown lettuce and spinach at the Absaraka location in March and April using the infrared heat strip with and without a low tunnel and a low tunnel without soil heating. Soil heating without a low tunnel did little to protect the greens from the very low minimum temperatures in the high tunnel. In contrast, greens within the low tunnels were alive and growing, and with soil warming dry matter accumulation was even greater.