High tunnels are plastic-covered, passive solar greenhouses used to modify the growing environment. Although U.S. growers are late adopters of this technology compared with Asia and the Mediterranean region, their popularity is rapidly expanding (Carey et al., 2009; Wittwer and Castilla, 1995). Many growers are exploring and using high tunnel systems to cultivate crops for local markets (Jett et al., 2004) as a result of the benefits, which include opportunities for season extension, crop risk reduction (e.g., weather and foliar diseases), and intensive production capabilities on limited land area (Blomgren and Frisch, 2007; Lamont, 2009).
High-value horticultural crops such as tomato are a common choice for cultivation under high tunnels because they can generate greater revenue compared with many other crops. This allows for a quick recovery of the initial investment and ongoing income to sustain management expenses. Capital investments in high tunnels can typically be recovered over 1 to 5 years (Blomgren and Frisch, 2007; Conner et al., 2010; Waterer, 2003).
A 2005–2007 survey of Midwest high tunnel growers reported that tomatoes were the most commonly grown high tunnel crop (Knewston et al., 2010) and trends in the fresh tomato market indicate increasing consumer demand for both organically grown and heirloom varieties (Calvin and Cook, 2005; Lucier, 2009; Lyson et al., 1995; Stevens-Garmon et al., 2007). Organic tomatoes often garner a 15% to 20% price premium over conventionally grown crops (Fernandez-Cornejo et al., 1994; Stevens-Garmon et al., 2007) and heirloom varieties are sold for up to $15.4/kg at specialty markets (Jordan, 2007).
Heirlooms are open-pollinated varieties that are valued for their unique colors, shapes, flavors, and legacies. Heirloom tomatoes typically lack shape uniformity and have thinner skins compared with more modern varieties, making them difficult to pack and transport over long distances. In addition, growing heirlooms can be challenging as a result of lack of disease resistance and lower yields compared with many modern varieties (Rivard and Louws, 2008). Despite the challenges in heirloom tomato production, customer demand for these varieties has increased over the last two decades, paralleling a rise in support for organic products and farmers’ markets (Jordan, 2007).
Currently, the organic market represents 4% of the total food sales in the United States [Organic Trade Association (OTA), 2011)]. Both the organic market and farmers markets have exhibited strong positive growth trends over the last two decades. Even during the recent economic recession (2009–2010), the organic fruit and vegetable market gained an 11.8% increase in sales, which represents $1.1 billion in new produce sales (OTA, 2011). Local and direct market sales outlets continue to expand. In the last 15 years, the number of farmers’ markets has increased by more than 400% and North Carolina currently ranks as one of the top 10 states for total number of farmers markets in the United States (Agricultural Marketing Services, 2011).
High tunnel technology is best explored at a regional level as a result of the opportunities and limitations presented by the local climate. Research studies that explore horticultural production under high tunnels in the United States indicate a variety of positive benefits. More than 1 month of early-season extension was reported for high tunnel production in New Hampshire tomatoes (Wells, 1991) as well as Kansas and Utah strawberries (Fragaria ×ananassa) (Kadir et al., 2006; Rowley et al., 2010). In addition, Florida strawberry yields were 54% greater and marketable fruit weight 69% greater in high tunnels compared with the field (Salame-Donoso et al., 2010). Flower and fruit production were accelerated for Southern highbush blueberry (Vaccinium corymbosum L.) in Georgia; however, the lack of nighttime freeze protection in the spring made the crop vulnerable to fruit abortion (Ogden and van Iersel, 2009). Minnesota production of high tunnel raspberries (Rubus fruticosus) benefitted from greater yields and extended seasons (Yao and Rosen, 2011) as well as increased fruit quality and decreased disease incidence for raspberry in Michigan (Hanson et al., 2011).
Information regarding high tunnel production systems in the southeast region is very limited. Exploration of the use of high tunnel systems would help growers who supply a growing regional market and take advantage of a lengthy, subtropical growing season. Therefore, our study objectives included a replicated, systems-level comparison of organic heirloom tomato production under high tunnels and the open field in eastern North Carolina (USDA hardiness zone 7b to 8a). Differences in crop yield and fruit quality were examined as well as microclimate and disease incidence.
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