2017 ASHS Annual Conference

High tunnels are increasingly being used to extend the growing season and protect crops from weather extremes. We previously determined that these structures can increase pepper yield relative to production under open-field conditions, and fertility needs can be met using either inorganic or organic amendments without affecting pepper yield. However, active soil organic matter and microbial activity decreased in plots receiving inorganic fertility amendments, whereas these properties increased in plots receiving organic fertility amendments derived from plant residues. In this study, soil collected from these trials was inoculated with Rhizoctonia solani and planted with snap bean to determine how differences in soil properties could affect disease severity in a susceptible crop. Plants grown in soil collected from the high tunnel were generally more susceptible to R. solani than plants grown in soil collected from the open-field, but there was no difference between the systems in plots that received the organic fertility amendment derived from plant residues. When soils were pasteurized prior to R. solani inoculation, there was no difference in disease severity between systems or treatments indicating that biological factors likely played a role in the differences observed. Consequently, rhizosphere soil was subject to a metatranscriptomic analyses to identify the active microbial community associated with snap bean roots and determine their potential functional role in the suppressive activity observed. Results indicate that Actinomycetales, Bacillales, and Pseudomanadales were enriched in soils that received the organic fertility amendment derived from plant residues, whereas Enterobactereacea were enriched in soils that received the inorganic fertility amendment. These results indicate that while high tunnels can increase crop productivity, soil health can be degraded over time making crops more susceptible to soil-borne and potential human pathogens unless plant residues are applied to improve or maintain soil health.