The effects of cover crops on soil arthropod communities in the Inland Pacific Northwest

View the project final report

Commodities

• Agronomic: barley, clovers, flax, peas (field, cowpeas), potatoes, sunflower, wheat
• Vegetables: lentils

Practices

• Crop Production: cover crops, crop rotation
• Education and Training: extension, networking, on-farm/ranch research, workshop
• Natural Resources/Environment: indicators
• Production Systems: agroecosystems, dryland farming, organic agriculture
• Soil Management: green manures, organic matter, soil quality/health
• Sustainable Communities: partnerships, sustainability measures

To improve farming sustainability and resiliency, growers in the Inland Pacific Northwest (IPNW) are transitioning from traditional cereal production systems by diversifying crops and rotations. Diversification with cover crops benefits soil health and increases agroecosystem resiliency. However, adoption of this alternative strategy is novel in the IPNW and it is unknown how aspirational crops and cropping systems impact belowground soil arthropod communities. Conserving soil arthropod biodiversity and function is critical to soil health, decomposition, nutrient cycling, and pest control and promotes plant productivity. This project will compare belowground arthropod community composition and functionality in soils under cover crops with soils from less intensive and less diverse “business-as-usual” practices on three, representative working farms over two-years. To complement the on-farm surveys, a replicated small-plot study will examine how cover crop taxonomic and functional diversity drives soil arthropod community dynamics. Finally, to tie soil arthropod community composition to function, manipulative field experiments will examine associations between arthropod biodiversity and residue decomposition. This study will be the first in the region to examine rigorously how cover crop diversity impacts the biodiversity of belowground arthropod communities and their contributions to soil processes. Results will be disseminated to regional farmers through outreach at cereal schools, field days, and extension literature, and to the scientific community via peer-reviewed publications and presentations at professional meetings. Outcomes will be more informed adoption and improved management of cover crops as a component of sustainable farming practices and improved understanding of arthropods in agricultural soils.

1. Determine how cover crops currently used by some producers in the IPNW affect soil faunal diversity. Working on three cooperating producers’ farms we will assess the effect of cover crops vs. BAU farming without cover crops on belowground arthropod biodiversity over two years. We will test the hypothesis that soil arthropod biodiversity is greater under cover crops than in the absence of cover crops.

2. Determine whether cover crops with greater plant species diversity have greater belowground arthropod biodiversity. In small-plot studies with collaborators at an NRCS site, we will assess the effects of experimentally manipulated cover crop diversity on the abundance and diversity of belowground arthropods. We will test the hypothesis that soil arthropod diversity increases in response to increased cover crop diversity.

3. Measure the association between soil arthropod diversity and a key soil ecosystem function, crop residue decomposition. On soils with differing belowground arthropod diversity as assessed in Objective 2 we will measure decomposition rates of a standardized cover crop residue. We will test the hypothesis that rates of residue decomposition increase with soil arthropod community diversity. In year 2 of the study, we will validate results on producer farms to provide them with information on arthropod-mediated residue decomposition rates in their fields.

4. Assess IPNW soil health using arthropods as bioindicators. The QBS-ar index will be used evaluate soils in cover crops and BAU farming and among treatments in the small plot study to demonstrate the applicability of this novel tool for assessing soil health in the IPNW.