Nitrogen Mineralization in Soils Used for Biofuel Crops

Perennial biofuel crops such as Miscanthus and switchgrass are thought to increase soil organic matter and therefore may increase soil nitrogen (N) mineralization rates. Our objective was to evaluate a range of N-mineralization indices for soils with established biofuel crops and compare these results with soils in a traditional corn and soybean rotation. We sampled surface soil (0-10 cm deep) from switchgrass (6 years after establishment) and Miscanthus plots (5 years) in a high-organic-matter Mollisol. The longest potential N mineralization index, a 24-day incubation, was significantly greater in Miscanthus soils compared to switchgrass and corn-soybean. In addition, 7-day anaerobic N and potassium chloride-extractable ammonium N were both greater in Miscanthus soils compared to switchgrass and corn-soybean. Our results do support our hypothesis that N-mineralization rates are greater in soils under biofuel production.