Low Tunnel Strategies for Microclimate Modification and Early Vegetable Production

Profitability of vegetable production in the North Central Region of the United States is limited by the temperate climate, which shortens the growing season. Therefore, most growers plant and harvest at the same time, which drives prices down (sometimes below breakeven point) and negatively affects, their income. The goal of this study was to improve profitability of fresh market vegetables in Michigan and the North Central Region.  We achieved this goal by developing, testing, and demonstrating new low tunnel strategies for frost protection and early harvest within an open field setting.  Low tunnels are a way for growers to start planting earlier, so they can harvest earlier, and receive a higher price for their produce before vegetable prices begin to decline.  This study tested black plastic mulch on raised beds along with various plastic materials used as low tunnels (clear and white perforated plastic) as well as their combination with a spun-bond material (for heat trapping) for frost protection and earliness in fresh market cucumber and tomato production . Results showed that by putting plastic mulch and our new low tunnel design (perforated plastic low tunnel plus a band of spun-bond plastic inside the tunnel) air temperature during frost events was increased up to 4^oF inside the tunnels.  Growing degree days were increased by 100 to 300 degree days and both tomatoes and cucumbers were harvested about 2 weeks earlier within the low tunnel treatments compared to the open control treatments. The fresh market price at the Detroit terminal was tracked and confirmed important drop in prices in the middle of the season compared to the beginning of the season. An economic analysis of the systems showed that the greatest total revenue was with the clear single layer treatment for cucumber and white dual layer treatment for tomato.  This study suggests that profitability of vegetable production can be improved with the use of low tunnels.