Evaluation of Legumes and Seedbed Preparation Impact On Sweet Sorghum Productivity.

Utilization of legumes as the nitrogen source for sweet sorghum should benefit the energy balance in this biofuel/bio-product production system. Two cool season legumes, crimson clover and hairy vetch, were evaluated as nitrogen sources for sweet sorghum.  Sweet sorghum yield and feedstock quality were measured when grown following legumes or utilizing commercial nitrogen fertilizer in both conventional and no-till production systems at the Macon Ridge Research Station in northeast Louisiana and Southeast Research Station in southeast Louisiana.  Legume biomass and total N and soil organic matter, soil nutrients, soil nitrogen and soil carbon were measured.  Hairy vetch tended to be more consistent in biomass production than crimson clover at the two locations.  The mean nitrogen fixation from the biomass of hairy vetch was 101 kg ha^-1 which was greater than crimson clover by 30 kg ha^-1.  Sweet sorghum planting may need to be delayed until May to allow the legumes to develop enough to provide adequate nitrogen.