A New Spin On An Old Crop for Bioenergy: Sorghum.

Seeking alternative and renewable sources of energy is necessary due to oil price fluctuations, environmental concerns, and national security concerns. Additionally, Southern U.S. agriculture has been negatively affected by drought conditions over the last several years. For these reasons, sorghum may be a reasonable alternative as an energy crop, because it is drought and nematode resistant. Sorghum could be integrated into a conservation system as part of a crop rotation with typical existing cash crops, where its biomass would be harvested for biofuel production. While much emphasis had been placed on perennials, annual crops could provide a major source of biomass for cellulosic bioenergy production.  New varieties of sorghum which are capable of producing extremely high amounts of biomass have not been fully investigated as part of Southeastern U.S. dryland conservation systems.  The types of sorghum evaluated were: grain sorghum (GS), high biomass forage sorghum (FS), and photoperiod-sensitive forage sorghum (PS).  Therefore, these different sorghums and a typical corn (Pioneer 31G65) were grown under two different tillage systems (conventional and conservation tillage) and with irrigated and non-irrigated treatments. Additionally, a rye cover crop was integrated to maximize biomass produced and to provide ground cover during the winter.

PS (26.04 Mg/ha) had the highest biomass production followed by FS (22.83 Mg/ha), GS (13.4108 Mg/ha) and corn (8.9270 Mg/ha) after 18 weeks of planting. All sorghum varieties showed higher dry biomass production than corn, which proved that sorghum was more efficient in extracting (non-irrigated condition) and in using (irrigated condition) water. Additionally, irrigation resulted in increased dry biomass production for any tested crop, with average increases of 4.86 Mg/ha. Different tillage systems applied did not affect the dry biomass production, which indicated that conservation tillage should be used because fuel, compaction, and erosion were all reduced with the conservation system.