Inorganic fertilizer sources of nitrogen (N) can be prone to losses through leaching and volatilization, resulting in detrimental effects on water quality and increased emissions of greenhouse gases. Although some research suggests that legume-based nitrogen sources may be less susceptible to such losses than conventional fertilizer N, mineralization of legume N may not necessarily coincide with crop uptake, making it vulnerable to off-site movement. In our research we hypothesize that retention of the residue from a small grain crop prior to a hairy vetch (Vicia villosa) green manure contribution will increase the carbon to nitrogen ratio of the overall residues, thereby promoting immobilization of nitrogen into the microbial biomass. In addition we hypothesize that light surface tillage of herbicide-killed vetch will reduce N losses due to denitrification by eliminating the anoxic microsites at the soil/vetch interface. Field studies are currently in place to evaluate the implications of C:N and tillage manipulations of the vetch residue on decomposition of the green manure and associated soil nitrogen dynamics.