Comparative Nutrient Use Efficiency by Candidate Biofuel Crops

Maximizing biomass yield while minimizing nutrient input represents a new challenge for bioenergy cropping systems. Our objective in this study initiated in 2007 was to determine if nutrient use by perennial and annual bioenergy crops was fundamentally different from well-characterized cropping systems. Using meta-analysis and field experimentation, we studied the relationships between N, P, and K uptake, biomass yield, and composition of sorghum, Miscanthus, and switchgrass. Maize was included as a control.

Meta-analyses revealed that nutrient uptake scaled with biomass production across species. Nutrient losses to the environment occurred when senescent biomass was harvested in winter. Miscanthus and switchgrass biomass yields often were not increased with N, P, and K fertilization. High yields of switchgrass were possible with low tissue K concentrations that favor pyrolytic conversion processes. Under low N, yield of sorghum lines exceeded that of maize. Photoperiod-sensitive and sweet sorghum lines produced nearly twice the dry matter of maize at 67 kg N/ha. System differences in nutrient responses should be exploited when deploying candidate biomass species onto marginal soils. IN-25F