Nitrogen is one of the most important nutrients for crop growth and is usually required in the greatest quantities for maximal biomass and grain production. Unfortunately, residual -N remaining in the soil after cash crop harvest is susceptible to loss through erosion, runoff, and leaching. Cover crops provide safeguards against N loses by serving as sinks for residual soil nitrate that could otherwise be lost from bare or fallow soils. The objective of this study was to evaluate the effects of cover crop species and fertilizer-N rate on the recovery and partitioning of N-labeled fertilizer from two different soils by cereal rye and radish cover crops under greenhouse conditions.