Nitrogen rate and harvest date effects on energy cane yield, quality parameters, nutrient uptake and biomass chemical composition

Enhancing energy cane biomass production can increase feedstock supply for lignocellulosic-based ethanol production. This study was conducted at the Louisiana State University Agricultural Center (LSU AgCenter) Sugar Research Station in St. Gabriel, LA, from 2013 to 2015 to evaluate yield, fiber composition, and nutrient removal rate of energy cane harvested at different dates. The treatments included two energy cane cultivars ('Ho 02-113' and 'Ho 72-114') and four N rates (0, 56, 112, and 224 kg N ha(-1)), arranged in split plot in a randomized complete block design with four replications. Fifteen plants were collected once a month beginning 2 mo prior to the harvest date and then separated into leaves and stalks and analyzed for fiber and nutrient composition. Harvest date, cultivar, and N rate significantly affected energy cane yield (stalk and leaves), quality components, lignocellulosic composition, and nutrient removal rate (p < .05). On average, harvesting energy cane 1 and 2 mo earlier than the scheduled harvest date reduced stalk yield by 4% and 20% and leaf yield by 3% and 15%. Minimal changes on stalk fiber content and lignocellulosic composition in response to the treatments were documented but no specific and consistent trend was established. With leaf included, energy cane biomass production was increased by 32%; however, this can result in significant removal of plant essential nutrients, particularly N (105 kg ha(-1)), P (16 kg ha(-1)), and K (116 kg ha(-1)). The long-term impact of complete removal of energy cane biomass from the field could result in decline in soil fertility and productivity.