Sorghum and kenaf biomass yield and quality response to nitrogen fertilization in the Northern Great Plains of the USA

There is increasing interest in reducing the inputs in potential biomass crops for bioenergy production, especially in areas with limited rainfall, Two sorghum types, forage sorghum (Sorghum bicolor L Moench), and sorghum x sudangrass (Sorghum bicolor. var. sudanense (Piper.) Stapf.), and kenaf (Hibiscus cannabinus L) were studied for their potential as feedstocks for biofuel production as they can be integrated into existing cropping systems. The objective was to evaluate the response to different N rates in their subsequent biomass output and quality components in four environments, Fargo and Prosper, ND, in 2010 and 2011 and at three growth stages (V8, R1, and harvest). The design was an RCBD with a split-plot arrangement and three replicates, with the crops as the main plots, and N rates as the subplots. Results indicated that both sorghums tested produced between 14 and 15 Mg ha(-1) of dry matter biomass averaged across N rates, while kenaf biomass yield was significantly lower at 7.4 Mg ha(-1). There was a significant response in biomass yield with increasing N rates. Ash content for all three crops decreased significantly at the later growth stages, decreasing from 119 mg kg(-1) at the earliest growth stage down to 79 mg kg(-1) at harvest. Neutral detergent fiber (NDF), acid detergent fiber (ADF), and hemicellulose increased at later growth stages for both crops. Kenaf had the greatest increase in NDF and ADF, from stage V8 to harvest. Forage sorghum and sorghum x sudangrass both had higher NDF, ADF, and hemicellulose than kenaf at each growth stage. Forage sorghum may serve as a feedstock for bioenergy production in the Northern Great Plains of the USA due to its high biomass yield and low lignin content. (C) 2013 Elsevier B.V. All rights reserved.