Test graduate-level understanding of biogeochemical processes controlling nitrogen cycling in temperate agricultural soils, including microbial and abiotic drivers (nitrification, denitrification, mineralization, immobilization), environmental controls (soil pH, texture, moisture, temperature, redox), management influences (fertilizer timing/rate, cover crops, tillage), common measurement approaches for N fluxes and pools, and implications for N losses, crop uptake, and mitigation; assess conceptual mechanisms, interactions, and interpretation of data.