Cellulosic Biomass and Ethanol Yield Response to Stover and Nitrogen Management in Continuous Corn.

Interest in producing ethanol from corn (Zea mays L.) cellulosic materials has spurred research questions regarding management decisions that maximize cellulosic biomass and ethanol production. Fertilizer N rate is one management variable that influences these yields. Estimates of cellulosic biomass and ethanol yield response to fertilizer N rate are available for the Upper Midwest, but they do not account for the effects of management variables such as stover and tillage management. Experiments were established in the fall of 2008 on tile drained clay loam soils grown under continuous corn at the University of Minnesota Research and Outreach Centers near Lamberton and Waseca, MN. Two stover management treatments (removed and retained), three tillage systems (disk-chisel, strip-, and no-tillage), and six fertilizer N rates (0 to 234 kg N ha^-1) were assessed. Stover biomass and ethanol yield required 28 and 7% less fertilizer N for agronomic optimization, respectively, with stover removal. These yields were generally maximized at fertilizer N rates lower than economically optimum N rates (EONR) for grain yield, regardless of stover management. Tillage did not affect stover characteristics. Neither stover nor tillage management affected the response of cob biomass and ethanol yield to fertilizer N rate. Cob ethanol yield was only maximized at or within EONRs for grain yield when stover was retained. These results indicate stover management has a greater effect on stover than cobs, and that tillage does not affect biomass or ethanol production, or their response to fertilizer N rate.