The sustainability of tropical maize as an alternative biofuel or silage crop

With increasing world population, the U.S. Department of Energy initiated the Energy Independence and Security Act (EISA) requiring by 2030 the replacement of 30% of petroleum based fuel sources with biofuel (USDA 2010). Tropical maize (Zea mays L.) has potential as a new biofuel crop for the Midwestern US. It is a temperate by tropical (or tropical by tropical) hybrid that retains the photoperiod sensitivity of tropical materials when grown in temperate regions, resulting in high biomass, but with delayed flowering that reduces or eliminates grain production. The reduced grain production results in accumulation of sucrose in the stalk and a lower nitrogen fertilizer requirement. Our objective was to evaluate the impact of sustainable practices such as conservation tillage, cover crops, and reduced nitrogen fertilizer application on tropical maize as a biofuel, biomass, or animal feed crop. Tropical maize hybrids have been characterized as: 1) dual purpose, producing high biomass levels with high quality grain that can be harvested for the grain and the stover used in a bale-burning furnace for thermal energy, or that can be ensiled for use as animal feed; and 2) high sugar, producing high biomass and high stalk sugar accumulation that can be used for ethanol production. The experiment was conducted in Champaign, IL in 2014 and 2015. The two hybrid types were planted into tilled strips evaluated under three nitrogen rates of 0, 67 and 202 kg N ha-1. Two annual cover crops, annual ryegrass and pennycress, were compared to a perennial ground cover, creeping bentgrass, and a no-cover control. Annual cover crops produced tropical maize biomass yields similar to the no-cover control regardless of hybrid. Animal performance was similar when fed tropical maize grown at a lower rate of nitrogen compared to conventional field corn silage. Results show that a management system that optimizes the environmental sustainability of tropical maize can be used while maintaining a competitive yield