Increased consumption of oil in the U.S., coupled with unstable world markets, justifies research and development of sustainable and economical fuel alternatives.  Global increases in the concentration of atmospheric CO₂ have lead to strong interest in assessing effects of land use and management practices on soil organic carbon (SOC) pools and flux. Bioenergy crops have potential as a sustainable fuel alternative to fossil fuels and offer the potential to mitigate green house emissions.  Special interest has been given to herbaceous and woody species as energy crops and a source of biofuel feedstock. The U.S. Department of Energy has interest in switchgrass (Panicum virgatum L.) as an energy crop due to its high biomass production, extensive root system, and the fact that it grows well in a variety of soils. Land management plays a direct role in the productivity and effectiveness of land used to produce biofuel. The principal objective of this field study was to assess these land management effects on SOC and N concentrations and pools under long-term studies of bioenergy crops on four northeast Texas soils in adjacent counties.  Soil analyses under switchgrass management were compared to soils under crop, pasture or forestland use on the same soil series.  Soil cores were collected across four soil series to 10-cm depth and were evaluated to determine bulk density, volumetric water content, and SOC and N pools. Results showed that carbon sequestration rates were higher for switchgrass when compared to other cropping systems within each soil type. Significant differences in bulk density, water content, C and N pools among soils and cropping systems (P<0.05) were also shown. There was a strong linear relationship between C and N pools for each soil type and land use.  Such empirical relationships, however, were soil and land use specific.