Aboveground Biomass Yield and Carbon and Nitrogen Accumulation in a Continuous Corn Stover Harvesting System.

Corn (Zea mays L.) biomass has many uses, including animal feed and bedding, grain ethanol production, and developing use for cellulosic ethanol.  However, stover harvest in addition to grain harvest creates uncertainty related to soil quality, sustainability, and nutrient cycling. The objective of this study was to evaluate the effect of different production practices on corn biomass yield, and accumulation of C and N. A three year experiment (2009-2011) was conducted at two Iowa sites. Treatments included two tillage systems (chisel plow and no-tillage), three corn stover harvest rates (0%, 50%, and 100%), and three fertilizer N rates (0, 165, and 275 kg ha^-1). Aboveground corn plant samples were collected at plant maturity, and separated into grain, cob, and vegetative components, with measure of biomass and C and N concentration. Results indicated an increase in total aboveground corn biomass, C, and N with increasing N fertilization rate, chisel plow tillage, and 50% or 100% stover harvest compared to no-tillage and 0% stover harvest. Treatments did not influence C concentration, but harvest of corn stover and higher N rates increased total N in the plant components. The partitioning of total plant C accumulation was 49%, 7%, and 44% for grain, cob, and vegetative components, respectively; while the N accumulation was 57%, 4%, and 39%, respectively. The harvest of corn stover reduced the optimum N fertilization rate by 22 and 45 kg N ha^-1 (9% and 18%), for the 50% and 100% stover harvest, respectively. In the short time period of this study, corn stover harvest increased biomass yield and N uptake, but reduced N fertilization requirement. These effects from stover removal, and in conjunction with continuous corn stover harvest, could affect soil on a long-term basis.