Switchgrass (Panicum virgatum L.) has become an important bioenergy crop. Warm, winter temperatures in the southeastern USA allow for fall establishment and winter growth of cool-season legumes that may provide nitrogen to the spring perenniating crop of switchgrass. Data indicates variation due to year and location, but hairy vetch plots provided a greater nitrogen percentage in the subsequent biomass production of switchgrass. In 2011, switchgrass fertilized with 56 kg ha-1 N was greater than the control and in 2012 it was greater than the 28 kg ha-1 N treatment. Variation around the means prevented clear separation among other treatments. The data also showed that hairy vetch had the greatest volunteer frequency and cover percentage throughout the year. Data from the Dairy Farm showed no differences in yields due to a lack of field management the previous years and only ball clover increased its coverage over time.