Soil Microbial Function and Community Composition Responses to Winter Legume Cover Crop under High Tunnel Pepper Production
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In order to meet increasing demands for locally grown food, many farmers are utilizing high tunnels, a steel-frame structure with a plastic covering. While high tunnels’ season extension capacity is beneficial, it may result in soil degradation due to intensive cropping. Legume cover crops are useful soil amendment tools that provide organic nutrients, although they are rarely utilized by high tunnel growers. This study focused on the effect of cover crops on soil microbial function and community composition under a high tunnel system in Minnesota. Three cover crop treatments – 1) red clover; 2) a mix of hairy vetch, winter rye, and tillage radish; and 3) a mix of Austrian winter pea and winter rye – were compared to soils without cover crop. Soil microbial function was measured by activities of three hydrolytic enzymes (β-1,4-Glucosidase, Cellobiohydrolase, β-1,4-N-Acetylglucosaminidase) and two oxidative enzymes (phenol oxidase and peroxidase). Microbial community composition was measured by phospholipid fatty acid (PLFA) analysis. We expected cover crop treatments to cause shifts in microbial properties. However, both enzyme activities and PLFA profile showed no treatment effect. This may indicate that 1) both sampling dates missed the timeframe during which the cover crop effect would be the strongest and/or 2) high tunnels mitigated the cover crop effect by providing protection against climatic effects. Overall, this study provides more focused direction for the future studies and thus adds to a small but growing body of work that will surely become more important in the face of a growing high tunnel economy.