Sustainable Agriculture Research and Education (SARE) 2022: Evaluation of Soil Solarization as a Sustainable Management Method for Pests, Pathogens, and Weeds in Southeastern High Tunnels

Evaluation of soil solarization as a sustainable management method for pests, pathogens, and weeds in southeastern high tunnels High tunnels (HTs) are used to help small farms in Kentucky and Tennessee increase their resiliency and give many the ability to extend their growing season for year-round production of high-value specialty crops. HTs are economical, semi-permanent, passively heated and cooled covered structures. Growers are often able to collect a premium price because the fruit quality is often better and the product is available before or after crops grown in the open field. While high tunnels are semi-permanent structures, many are never moved due to cementing corner posts into the ground to secure the structure from weather events, land constraints and/or the time and labor required to move them. Continuously growing in non-rotated soil can intensify and worsen pathogen, pest, plant-parasitic nematode, and weed population densities. Soil solarization is a management technique that uses passive solar heating of irrigated soil under transparent plastic tarping to achieve temperatures detrimental to soilborne pests, pathogens, and weeds. This technique has been shown to be effective in warmer climates. As temperatures in HTs are much warmer compared to outside temperatures, solarization may be effective in HTs in more moderate transitional zone climates like in KY and TN. Moreover, there may be potential to solarize individual beds in a tunnel, as a particular crop concludes, before planting another crop in that bed. Individual bed solarization, if effective, could be move appealing to growers than the opportunity costs of solarizing an entire tunnel. However, the optimal timing and approach for solarization in HTs in our region are unknown. We will investigate solarization during different seasons (spring, summer, and fall) as well as different durations (two and four weeks) to effectively manage various pathogens, pests, and weeds. Soil temperatures at three depths (2, 4, and 6 inches) will also be monitored, as different pests and pathogens are impacted by different temperatures. This project will help us determine if solarization is effective against our most problematic pathogens, pests, and weed seeds, sustainable to implement, and adoptable at the farm level. There are opportunity costs of taking HTs out of production for up to four weeks during a growing season in order to solarize, so we also will evaluate the economic feasibility of solarization. We will work collaboratively with grower cooperators to discuss optimal timing and duration for solarization based on their HT crop and production schedules. Extension and outreach materials will include YouTube videos about solarization implementation, pros and cons, and things to keep in mind as well as a solarization factsheets tailored with the specific results from our trials. We will also present the results alongside our grower collaborators at grower conferences, including the Kentucky Fruit and Vegetable Conference and the Pick TN Conference, and field days (UT Steak and Potatoes Field Day and UK Horticulture Research Farm Field Day).