Smith, L. C., R.D. Jackson, J. Hedtcke, J. Posner , and T. Balser
Presented at the GLBRC Sustainability Retreat (2010-02-10 to 2010-02-12 )
Nitrogen fertilizer is expensive and an aquatic and atmospheric pollutant, so understanding how bioenergy crops respond to N inputs is a key sustainability consideration. On very productive mollisols at Arlington Ag Research Station in WI, we harvested biomass at 2 times (Aug and Oct 2009) from 3-y old switchgrass and 10-y old high-diversity prairie receiving 0, 50, or 150 kg N –ha fertilizer rates. We used regression tree analysis and linear models to assess the relative effects of harvest timing, N fertilization rates, and site scores from a 2-axis non-metric multidimensional scaling solution (an index for plant community composition). We found that N fertilizer did not improve diverse prairie yields but significantly improved yields for October-harvested switchgrass. Diverse prairie and switchgrass produced higher yields when harvested in August than October. We also found that species composition influenced yield more than fertility management for diverse prairie harvests and August-harvested switchgrass.
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