Nitrogen Rate and Harvest Date Effects on Energy Cane Yield, Quality Parameters, and Biomass Chemical Composition.

One of the essential facets to achieve full-scale commercialization of lignocellulosic-based biofuel industry is the accessibility to year-round supply of high quality feedstock. Depending on crop age, cane is harvested between October to December thus the supply of feedstock from this energy crop may be available for only few months during the year. A study was initiated in 2012 at the LSU AgCenter Sugar Research Station in St. Gabriel, Louisiana to: a) evaluate if harvesting energy cane one- and two-months earlier than the scheduled harvest date affects its quality parameters, yield, and biomass chemical composition, and b) determine if there is any interactive effect between N rates and harvest dates. The experiment with a 2 x 4 factorial treatment structure was arranged in split plot in a randomized block design with four replications. The treatments included two energy cane varieties (Ho 02-113 and US 72-114) and four N rates (0, 56, 112, and 224 kg N ha^-1). Fifteen stalks were collected once a month beginning two months prior to the harvest date and were separated (into leaves and stalks), weighed, processed, and analyzed for biomass composition (ANKOM²⁰⁰⁰) and sugar quality parameters. For both varieties, N fertilization resulted in an average of 35 Mt ha^-1 yield increase (P<0.05). Harvesting cane at earlier schedule increased tonnage but reduced Brix, sucrose and fiber content. The significant reduction in sucrose content of US 72-114 was observed with the application of 112 kg N ha^-1 while it was at 224 kg N ha^-1 for Ho 02-113.  The negative effect of N on cellulose and hemicellulose was only observed on variety Ho 02-113 harvested two-months earlier than the scheduled harvesting. Our initial results suggest that extending the harvest schedule to earlier dates can potentially compromise cane production for energy due to reduced quality of biomass lignocellulosic composition.