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

Northwestern Washington State is home to 11,000 acres of fresh market potatoes, which is the region’s highest valued crop. Producing blemish-free potatoes requires intensive soil cultivation to break up compaction, but unfortunately, these management practices can lead to a decline in soil health and, potentially, arthropod diversity and abundance. In 2021, the Long-Term Agroecological Research and Extension (LTARE) site in Mount Vernon, WA was established to examine the impacts of four potato-based crop rotation systems with varying levels of disturbance and organic matter inputs: System 1) full-tillage and no cover cropping; System 2) full-tillage, cover cropping, and incorporation of crop residues; System 3) reduced tillage, cover cropping, and increased organic matter inputs; and System 4) no-till, perennial cover crop after a potato rotation. Our study focused on how these systems affected the diversity and abundance of soil-associated arthropods, such as Carabidae, Collembola and Oribatida. In the summer of 2024, we used pitfall traps to survey ground arthropods in potato fields preceded by the four rotational systems. We found an increase in total carabids per pitfall trap in potatoes preceded by long-term cover crops with minimal disturbance events and higher organic matter inputs (System 4), compared with potatoes preceded by all other systems with higher disturbance and lower organic matter inputs (Systems 1-3). These results suggest that potatoes preceded with decreased disturbance and long-term cover crops can increase arthropod activity abundance, which may lead to more effective biological control in potatoes.