2017 ASHS Annual Conference
Effects of Low Tunnel Plastic Type on Organic Production of Day-neutral Strawberries in the Upper Midwest
Effects of Low Tunnel Plastic Type on Organic Production of Day-neutral Strawberries in the Upper Midwest
Friday, September 22, 2017
Kona Ballroom (Hilton Waikoloa Village)
Demand for local, organic strawberries (Fragaria x ananassa) can be difficult to meet in the Upper Midwest, where short growing seasons limit production. Historically, strawberry growers in this region have been restricted to the hardiest June-bearing cultivars, which only produce fruit for a few weeks in the early season. However, recent research on day-neutral strawberries has shown that these cultivars can be successfully grown as annuals in the Upper Midwest by using a low tunnel protected culture system. Low tunnel structures create a microclimate more favorable to strawberry production, protecting plants from rainfall. Specialty plastic types available for use as low tunnel coverings offer a variety of options for influencing the quality and intensity of light reaching plants under the tunnels. In particular, some plastic types are formulated to block or transmit different amounts of light in the ultraviolet (UV) A and B ranges. The objectives of this study were to evaluate how variance in light intensity and quality, as modified by characteristics of different plastic coverings, affect the microclimate, fruit yield and quality, and insect pest presence in an organic strawberry production system. In this study, twelve strawberry plots were maintained with one of three main treatments applied: low tunnel with UV-blocking plastic covering, low tunnel with UV-transmitting plastic covering, or no low tunnel covering. Microclimate characteristics did not vary significantly among main treatments in terms of average temperature, humidity and dew point levels, but there was variation in daily highs. Light intensity in the Photosynthetically Active Radiation (PAR) range was highest in the open plots, but not significantly different between plots covered by UV-transmitting plastic versus by UV-blocking plastic, whereas light intensity in the UV range was significantly different among all main treatments, as expected. For the most part, insect pest presence was not affected by the type of covering over the tunnels. Though yield did not vary significantly among main treatment types, fruit quality did, with the highest percentage of marketable fruit seen in plots covered by UV-transmitting plastic, followed by UV-blocking plastic, followed by uncovered. These findings will help growers make decisions about what plastics to use to optimize low-tunnel strawberry production in cold climate states. We conclude that a plastic covering transmitting some amount of UV light is preferable both to a plastic covering blocking all UV light and to no plastic covering at all.