Grafting and Number of Layers of Polyplastic Film Affected Growth and Yield of Heirloom Tomatoes in High Tunnels

High tunnels have become a powerful tool allowing season extension for vegetable growers. The USDA NRCS High Tunnel Environmental Quality Incentives Program has greatly increased the number of high tunnels in Missouri. Despite the size and style of high tunnels, farmers have to choose either a single-layer or double-layer of polyplastic film as a covering. Tomato grafting is an emerging technique in the United States which has the potential of providing disease resistance and enhancing vigor and yield for heirloom tomatoes in high tunnels, where rotation is limited. The objective of this study was to investigate the effect of grafting and the number of layers of polyplastic film on growth and yield of high tunnel heirloom tomatoes. Heirloom tomatoes German Pink and Ananas Noire were grafted onto Beaufort, Maxifort, and Emperador rootstocks in March 2011. Grafted transplants were then planted in two 30’ x 96’ Zimmerman brand high tunnels (with ridge-vents) covered with either a single-layer or double-layer 6mm polyplastic film. The growth and yield of the two heirlooms were affected by grafting and the layers of plastic. Ananas Noire/Emperador had the highest yield in both tunnels while Ananas Noire/Beaufort had a higher early yield in the double-layer plastic tunnel. German Pink had similar yield regardless of rootstocks in the single-layer plastic tunnel, but it yielded most when grafted onto Beaufort in the double-layer plastic tunnel, although yield was higher for all grafted plants. Summer 2011 was extremely hot, which might have contributed to the productivity of grafted and non-grafted tomatoes in the high tunnels with different layers of plastic.