Response of Corn Grain, Cellulosic Biomass, and Ethanol Yields to Nitrogen Fertilization

Corn (Zea mays L.) stover will likely play an integral role in near-term attempts to produce renewable cellulosic transportation fuels. However, little is known regarding the effect of N fertilization on biomass and ethanol yields of stover and cobs. The objectives were to evaluate the effect of N fertilization on stover and cob biomass and ethanol yields across a range of environments, and to determine if these biomass and ethanol yields can be maximized within N fertilization rates for grain yield optimization. Field experiments were conducted over eight diverse environments across Minnesota. Overall, stover and cob biomass and ethanol yields increased with increasing N fertilization, and agronomically optimum nitrogen rates (AONR) were identified in nearly all environments that were responsive to N fertilization. Ethanol yields for stover ranged from 2414 to 3842 L ha(-1), whereas ethanol yields for cobs ranged from 513 to 906 L ha(-1). When AONRs for stover and cob ethanol yields were compared to the respective AONR for grain yield, stover ethanol yield was maximized at N fertilization rates below the AONR for grain yield in four of the seven responsive environments, while cob ethanol yield was maximized at N fertilization rates below the AONR for grain yield in five of the six responsive environments. These results suggest that stover and cob ethanol yields will often be maximized when grain yield optimization is the primary goal.