Responses of soil faunal food webs to pesticide seed treatments

View the project final report

• 2013 annual report
• 2014 annual report
• 2015 annual report

Commodities

• Agronomic: corn, soybeans

Practices

• Crop Production: application rate management, nutrient cycling
• Education and Training: demonstration, extension, mentoring
• Natural Resources/Environment: biodiversity
• Pest Management: competition
• Soil Management: nutrient mineralization, soil analysis, soil quality/health

Conventionally managed annual row crop systems often rely heavily on synthetic fertilizers, pesticides, and tillage to produce consistent cash crop yields. The cumulative impacts of agricultural management may reduce the functional stability of soil faunal communities by constraining successional processes and altering consumer-prey relationships. Soil fauna inhabit multiple trophic levels and contribute to a diversity of agriculturally important functions including decomposition and nutrient cycling. This proposed research will determine how pesticide seed treatments affect soil faunal food web structure and its capacity to function. The main objective of this research is to determine if pesticide seed treatments reduce soil food web diversity leading to reductions in rates of decomposition and nitrogen cycling. A field experiment will be conducted at Penn State University’s Russell Larson Agricultural Research Center in Rock Springs, PA. This experiment will test the effects of pesticide-treated versus untreated crop seeds on soil food web composition and function. Characterization of soil faunal communities and structure will involve faunal extractions via Tullgren-Berlese funnels, identification to family, isotopic analyses, and food web modeling. Food web function will be measured using decomposition bags (litter decomposition) and ion exchange resin strips (nitrogen cycling). Our results will provide farmers with practical information regarding the direct and indirect effects of pesticide seed treatments on soil food web communities and their capacity to function in agricultural systems. More broadly, these data will advance the development of sustainable agricultural management strategies and our understanding of multi-trophic soil food web dynamics and its relationship to ecological stability.

Sustainable agricultural production will require reductions in the use of external inputs while simultaneously bolstering ecological processes that benefit crop production including succinct nutrient cycling between the soil food web and cash crops. To reach this goal, we must critically examine our current agricultural practices to determine how they affect the ecosystem services farmers rely upon. This research will explore changes in soil faunal food web diversity, structure, and function following pesticide seed treatments. Broadly, we hypothesize that pesticide seed treatments will reduce the diversity and functional capacity of soil faunal food webs via less diversified consumer-resource links. Our specific objectives are to:

1. Determine if pesticide seed treatments reduce soil food web diversity and complexity, measured by species richness and abundance, via direct and indirect pathways;

2. Determine whether pesticide treated seeds foster soil food webs with less diversified consumer-resource links;

3. Ascertain if the loss of diversity and simplified consumer-resource links reduces the food web's capacity to perform agriculturally important ecosystem services including decomposition and nitrogen cycling.

With a combination of field experiments and modeling, we will address these objectives to further our understanding of the effects of pesticide seed treatments on in situ soil food web composition, structure, and function.