Evaluating impacts of management practices on soil-associated arthropods in northwestern Washington potato-based systems

Western Washington State is home to 12,000 acres of fresh market potatoes, which are the region’s highest valued crop. The production of blemish-free potatoes requires intensive cultivation to break up compaction. Unfortunately, these management practices, along with a shortened crop-rotation cycle, can lead to the degradation of soil health (e.g., water-holding capacity, nutrient availability, and pH levels). To address stakeholder concerns and observe gradual changes in soil quality, the Long-Term Agroecological Research and Extension (LTARE) site in Mount Vernon, WA examines four management systems within a potato-based rotation. The following treatments are based on a gradient of soil disturbance and organic matter inputs: System 1 with full-tillage and no cover cropping, System 2 with full-tillage, cover cropping and incorporation of crop residues, System 3 with reduced tillage, cover cropping, and increased organic matter inputs, and System 4 with a no-till, perennial cover crop after a potato planting. This study examines potential treatment differences within each crop type using pitfall traps for soil-associated arthropod populations: carabids, staphylinids, spiders, centipedes, millipedes, collembolans, oribatids, and predatory mites. We hypothesize that the management practices intended to improve soil quality will increase arthropod diversity and abundance, which may contribute to biological control of pests and nutrient cycling. Our preliminary findings suggest that the perennial grass clover leads to greater abundances of beneficial arthropods once the plots return to potatoes. Further processing of 2023 and 2024 samples will demonstrate impacts of treatment differences in diversity and abundances of soil-associated arthropods.