Macroarthropod decomposers in field crops: Influence on residue breakdown and response to prophylactic insecticides

View the project final report

• 2016 annual report

Commodities

• Agronomic: corn, soybeans

Practices

• Crop Production: cover crops, no-till, nutrient cycling
• Natural Resources/Environment: biodiversity, carbon sequestration
• Pest Management: chemical control
• Production Systems: agroecosystems
• Soil Management: nutrient mineralization, organic matter, soil analysis, soil chemistry

With conventional tillage practices, cover crop residues are mechanically turned under and shredded, which promotes efficient microbial decomposition. In contrast, no-till systems rely solely on biological degradation to decompose cover crop residues. Despite its many benefits, reduced tillage concentrates residues at the soil surface, decreasing microbial access and slowing decomposition and nutrient cycling. As in natural systems, efficient shredding and incorporation of plant residues depends on the activity of macro-decomposers including millipedes, terrestrial isopods, and earthworms. Limited research focuses on macro-decomposer communities in agroecosystems, but their greater potential importance in reduced tillage systems warrants attention. The purpose of this proposed research is to define macro-decomposer communities in maize and soybean fields in the Northeastern United States, and understand their role in residue breakdown and nutrient cycling. If their role is as significant as my advisor and I suspect, disturbances to the macro-decomposer community may reduce soil quality, slow residue turnover, and exacerbate pest problems common to reduced tillage systems; therefore, in addition to defining macro-decomposer communities in reduced tillage maize and soy, we will conduct complementary field tests and toxicity assays to investigate the influence of prophylactic insecticides on macro-decomposer community composition and decomposition. Many farmers view these insecticides as necessary inputs that enhance yield, but recent research indicates that preventative insecticide applications can disrupt natural control with cascading effects that can decrease yield. My research will further scrutinize insecticide use that is outside of an integrated pest management framework, identifying their influence on macro-decomposer communities and functions in agroecosystems.

I will pursue four complementary, but independent objectives to define the macro-decomposer communities in Northeastern agricultural fields, the role of these communities play in decomposition and nutrient cycling, and their susceptibility to preventative insecticides.

Objective 1: Define the decomposer communities in conventional soy and maize fields of the Northeastern U.S., and Pennsylvania in particular.

Objective 2: Determine the influence of macro-decomposers on decomposition characteristics, including residue breakdown rate, nutrient mineralization, and production of soil organic matter.

Objective 3: Determine the acute sensitivity of representative macro-decomposers to the pyrethroid lambda-cyhalothrin and the neonicotinoids clothianidin and thiamethoxam.

Objective 4: Assess how prophylactic insecticide use (neonicotinoid seed treatments and post-planting pyrethroid applications) affects macro-decomposer community composition and decomposition.

Budget will cover: Transportation to and from the research farm site (all objectives), undergraduate research aid (all objectives), and soil tests (objective 2).