In order to meet the growing demand for energy globally, it is essential to find alternate and renewable sources of energy. Sweet Sorghum (SS) (Sorghum bicolor (L.) Moench Saccharatum Group) biomass is evaluated for conversion to ethanol. SS requires less Nitrogen (N) and Water as compared to corn and has potential to produce more biomass and ethanol per acre. The objective of this study is to evaluate the possibility of estimating yield based on leaf nitrogen (N), plant height, plant density and leaf number if there is a positive correlation between the yield and plant phenology and leaf N content at different growth stages. The SS was planted in early summer on Mecklenburg sandy loam soil (fine, mixed, thermic ultic hapludults) in Guilford County, NC in year 2010 and 2011 seasons. The experiment was conducted using a split plot and strip plot designs with main plot factor variety (Dale and M81-E) and subplot factor fertilizer rates (0, 100% Recommended Rate of Fertilizer*, 50% RRF+ Bio-Fertilizer and 100% RRF+ Bio-Fertilizer) and four replications. The phenological observations and plant N contents are measured three times (6, 10, and13 weeks after planting) in year 2010, biweekly in year 2011. In season 2010 biomass yield showed significant (p=0.0175) differences between the treatments of each variety. The data collected including 2011 season will be presented and discussed validate the patterns observed.