Bioenergy is becoming a very important aspect of alternative energy.  Soil organic carbon is essential for sustaining the bio-energy cropping system.  We conducted a study to determine the effect of different bio-energy crops with various nitrogen sources on dissolved organic carbon, carbon mineralization, and active carbon.  We evaluated high biomass sorghum, high biomass sorghum rotated with soybeans, switchgrass, eastern gamagrass, and switchgrass and big blue stem mix. The nitrogen sources used were urea, pelletized poultry litter, and municipal biosoilds.  Samples were taken from the 0-10 cm depth. Active carbon evaluated using the potassium permanganate method, carbon mineralization was determined by incubation for 28 days and dissolved organic carbon was extracted with water analyzed on a TOC analyzer.  Results will be discussed from the third year growing season of the bioenergy crops.