Earthworm Influences on Nitrogen Mineralization in Agroecosystems.

Earthworms have been shown to increase soil quality and crop yields in agroecosystems, primarily through enhanced rates of nitrogen (N) mineralization. Earthworms can increase N mineralization through burrowing, feeding, and casting activity. The soil under direct influence of earthworms is referred to as “drilosphere soil” and often has greater carbon, nitrogen, and microbial activity as compared to bulk soil. Recent work suggests that the common definition of drilosphere soil, soil extending 2 mm from burrows, may underestimate earthworm effects. A greenhouse mesocosm experiment will be conducted with N¹⁵-labelled wheat straw to monitor N mineralization rates and the transfer of N between litter, earthworm, and microbial pools. The anecic earthworm Lumbricus terrestris and endogeic Aporrectodea trapezoides will be studied. Carbon and N will be analyzed in earthworm tissue, microbial biomass, soil, and casts to determine N mineralization and track N over time. Fine-scale sampling will be conducted to better define drilosphere soil in terms of C and N enrichment. Overall, this data will provide valuable information on how earthworms of different ecological habits influence N cycling processes in agroecological systems. In addition, greater knowledge of drilosphere soil will help us quantify the overall impacts of earthworms on soil and plant growth.