2018 ASHS Annual Conference

The utilization of high tunnels is growing across the United States and is particularly important for facilitating an expanding local food production system. The benefits of season extension and/or environmental protection have been shown to improve crop productivity characteristics within a number of fruiting vegetables and leafy crops. However, there are sporadic reports of inconsistent and/or negative impacts on nutritional quality when compared to the open-field. In particular, UV light can affect antioxidant capacity and other phytochemical production. The goal of this project was to evaluate the impact of different polyethylene films (standard poly, diffusion poly, clear poly (no UV blocking), UVA + UVB blocking (<380-400 nm)), as well as 55% shade cloth and a simulated movable tunnel on light, temperature, crop yield, shelf life, and nutritional quality of tomato and lettuce. Trials were conducted in 2017 (summer tomatoes, fall lettuce) at the KSU Olathe Horticulture Center in four, 12’ x 130’, seven-foot tall high tunnels. The trials were arranged in a RCBD and each tunnel served as a replication. Average soil and canopy temperatures were affected by high tunnel covering and the average soil temperature was higher in the plots where the clear poly was used (P<0.001). The plants grown with 55% shade cloth (applied 6 WAP) had dramatically lower marketable tomato fruit yield than all the others with the exception of the UVA + UVB blocking poly (P<0.05). Similar results were seen with lettuce (P<0.001) and visual observations show varying levels of red color in ‘New Red Fire’ whereas green lettuce, ‘Two Star’ was generally unaffected. There were no significant differences in ascorbic acid (vitamin C) amongst the different treatments for tomato. High tunnel production systems offer a unique opportunity to manipulate light with various coverings such as different polyethylene films and/or shade cloth that typically cannot be accomplished in the open-field. In order to address production limitations, a further understanding of the impact of light on vegetable crops will be instrumental to furthering local and regional production of fresh-market vegetables.