Nitrogen Application Rate and Genotype Effects on Switchgrass Production and Chemical Characteristics

Abstract

Switchgrass ( Panicum virgatum L.) is considered as an important biofuel crop but further studies on factors that may have an effect on agronomic performance and energy attributes are needed to help elucidate management strategies for the crop. A 2-yr field study at the Brown Loam Branch Experiment Station, Raymond, Mississippi, USA, quantified the effects of four N application rates and four genotypes on biomass yield, ethanol yield, and nutrient removal of switchgrass. Biomass yield response to N rate was linear in 2008 and quadratic in 2009. Among genotypes, biomass yield averaged across N rate and years, ranked lowland NF/GA992 (13.9 Mg·ha -1 ) = lowland NF/GA001 (13.4 Mg·ha -1 ) > lowland Alamo (11.5 Mg·ha -1 ) > upland Cave-in-Rock (6.1 Mg·ha -1 ). There was no effect of N rate on tissue mineral concentrations but there was an N rate effect on Ca and Mg removal. Also, N use (biomass yield produced per unit N applied) and recovery (N removed in biomass) declined as N rate increased. Total ethanol yield was the greatest in Alamo (165.8 L·Mg -1 ) and averaged 162.0 L·Mg -1 for the other three genotypes. Total ethanol production was related more to biomass yield than chemical composition differences and was similar among lowland genotypes but different from Cave-in-Rock in 2008 (1.7 vs. 0.9 kL·ha -1 ) and 2009 (2.6 vs. 1.1 kL·ha -1 ). Feedstock grown from lowland Alamo, NF/GA001 or NF/GA992 produced greater biomass yield and ethanol as well as greater N use efficiency and recovery. These results indicate that there is opportunity to increase switchgrass biomass production through genotype selection and N management.