The implementation of high tunnels has shown to increase marketability and/or yield of tomato (Solanum lycopersicum) and lettuce (Lactuca sativa) crops compared with open-field systems. These structures provide the opportunity to alter light intensity and spectral quality by using specific polyethylene (poly) films and/or shadecloth, which may affect microclimate and subsequent crop productivity. However, little is known about how specific high tunnel coverings affect these parameters. The overall goal of this study was to evaluate the impact of various high tunnel coverings on the microclimate and crop productivity of tomato and lettuce. The coverings included standard, ultraviolet (UV)-stabilized poly film (standard); diffuse poly (diffuse); full-spectrum clear poly (clear); UV-A/B blocking poly (block); standard + 55% shadecloth (shade); and removal of standard poly 2 weeks before initial harvest to simulate a movable tunnel (movable). Microclimate parameters that were observed included canopy and soil temperatures, canopy growing degree-days (GDD), and photosynthetic active radiation (PAR), and crop productivity included yield and net photosynthetic rate. Hybrid red ‘BHN 589’ tomatoes were grown during the summer, and red ‘New Red Fire’ and green ‘Two Star’ leaf lettuce were grown in both spring and fall in 2017 and 2018. Increased temperature, GDD, and PAR were observed during the spring and summer compared with the fall. The soil temperatures during the summer increased more under the clear covering compared with the others. For tomato, the shade produced lower total fruit yield and net photosynthetic rate (Pn) compared with the other treatments, which were similar (P < 0.001 and <0.001, respectively). The greatest yield was 7.39 kg/plant, which was produced under the clear covering. For red leaf lettuce grown in the spring, the plants under the clear, standard, and diffuse coverings had significantly greater yield than the movable and shade coverings (P < 0.001). The coverings had less effect on the yield during the fall lettuce trials, which may have been attributed to the decrease in PAR and environmental temperatures. The findings of this study suggest that high tunnel coverings affect both microclimate and yield of lettuce and tomato.

(1) Background: We assessed the impact of high tunnel coverings and harvest maturity (breaker and light red) on antioxidant capacity, ascorbic acid (AsA), lycopene, β–carotene, and phenolic compound (flavonoid and phenolic acid) accumulation in tomatoes (Solanum lycopersicum) at harvest and postharvest. (2) Methods: The two-year study in Olathe, KS, included six different coverings: a standard polyethylene (standard poly), diffuse poly (diffuse), clear poly (clear), UV-A/UV-B blocking poly (block), 55% shade cloth + standard poly (shade), and removal of standard poly two weeks prior to harvest (movable). (3) Results: Antioxidant capacity increased in fruit grown under the clear covering, compared to the shade covering (p < 0.05); similarly, AsA accumulation increased under the standard and clear coverings, relative to the movable and shade coverings (p < 0.001). Postharvest, at the point of consumption (POC), rutin increased in fruit harvested at light red stage versus breaker stage (p < 0.001), and chlorogenic acid increased in light red harvested fruit by 60% under movable, 55% under shade, and 43% under block covering than breaker harvested fruit (p < 0.01). (4) Conclusions: Based on these results, we conclude that both high tunnel covering and postharvest maturation alter antioxidant capacity, AsA, lycopene, and phenolic compound accumulation profiles by the POC.

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The objective of this study was to investigate the effect of high-tunnel production on preharvest losses and harvest quality of two tomato (Solanum lycopersicum) cultivars. Our results indicate that using high tunnels for tomato production can reduce the preharvest food losses for this crop compared with open-field production, as indicated by increased productivity and percent marketability during the span of three production seasons. The tomato harvest quality did not differ in terms of physical attributes. However, open-field–grown tomatoes demonstrated a significantly greater antioxidant capacity when compared with the high-tunnel–grown tomatoes.