Evaluating impacts of soil management and crop rotation practices on soil-associated arthropods in Northwestern Washington potato systems

Adriana Barsan

Fresh-market potatoes (Solanum tuberosum L.) are a high-value specialty crop that contribute significantly to the agricultural industry in northwestern Washington, particularly Skagit County where there are around 10,000 acres per year. To investigate and optimize soil management strategies for potato-based systems over time, the Long-term Agroecological Research and Extension (LTARE) site was established at the Washington State University Northwestern Washington Research and Extension Center (NWREC) in Mount Vernon, WA in 2021. Soil health management also affects arthropod communities, which has implications for pests and beneficial insects within agricultural fields and the greater ecosystem. We sampled a wide range of arthropods within the soil and at the soil surface across three years, 2023-2025. Of all the species sampled, we focused on three arthropod groups, ground beetles (Coleoptera: Carabidae), springtails (Entognatha: Collembola), and oribatid mites (Acari: Oribatida), to assess the impacts of soil management practices. In Chapter one, we introduce potato production and management practices in northwestern Washington and provide an overview of the LTARE experimental design and objectives. In Chapter two, we examine how crop type and soil management systems in potatoes impact carabid genera. In Chapter three, we investigate how soil management systems in potatoes influence soil microarthropods. Though sample period varied, our pitfall trap results showed that System 4 (low disturbance/very high organic matter additions) most frequently increased carabids, collembolans, and oribatids compared to management systems with increased disturbance and lower organic matter additions (although not always). Additionally, the soil core sample results in potatoes demonstrated that Systems 2 (high disturbance/medium organic matter additions) and System 3 (medium disturbance/high organic matter additions) often increased collembolans and oribatid mites within the soil matrix. Overall, our findings demonstrate that within a single rotation cycle, common crop rotation and soil management practices that reduce disturbance and increase organic matter (e.g., perennial cover crop rotations) are more likely to support arthropod communities, even during a high disturbance crop like potato. This can have economic implications for growers by increasing biological control of pests alongside other ecosystem services associated with soil arthropod fauna, and thus, should be considered by the agricultural community when making crop rotational choices.

Evaluating impacts of soil management and crop rotation practices on soil-associated arthropods in Northwestern Washington potato systems

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