Smith, L.C., J. Posner, J. Hedtcke, T. Balser, and R. Jackson
Presented at the All Scientist and GLBRC Sustainability Meeting (2009-05-05 to 2009-05-07 )
Switchgrass and diverse prairie are candidates for cellulosic ethanol production, which could lead to significant changes in land use and land cover. Whether it is established CRP perennial grass stands or newly-planted biofuel cropping systems, the sustainability of harvesting these agroecosystems for biomass is in question. While much is known about these ecosystems in unmanaged settings, it is critical to understand how biomass can be produced and harvested without degrading soil resources and contributing to leaky nutrient cycling. Understanding the consequences of repeated biomass harvests and replacing the nitrogen exported in the harvested biomass with inorganic nitrogen fertilizers could improve how we manage these cropping systems to promote nitrogen conservation in order to address the ecological and economic benefits of nutrient retention and reducing nitrogen losses. To better realize which management scenarios will promote nitrogen conservation in these cropping systems, we will compare soil and plant nitrogen pools and the changes in the microbial community under experimental combinations of plant diversity, harvest timing, and nitrogen fertility. Since these native grasses are adept at thriving on endogenous N sources, we expect that managing them for biofuel production will affect the microbial interactions and nitrogen stores that help create tight nitrogen cycling and affect the nitrogen sources available for plant uptake. We hope to shed some light on the trade-offs between maximizing biomass production for biofuels and nitrogen retention in these agroecosystems while striving towards making best-management recommendations for cellulosic biofuel production.
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