Gallagher, M.E., W.C. Hockaday, C.A. Masiello, C.P. McSwiney, G.P. Robertson, and J.A. Baldock
Presented at the All Scientist and GLBRC Sustainability Meeting (2009-05-05 to 2009-05-07 )
Nitrogen fertilizer increases the yield of biomass produced by corn plants. Here we show that application of fertilizers can nonlinearly alter ecosystem biochemical stocks (i.e. carbohydrates, proteins, lipids, lignin, etc.) in all corn fractions (grain, reproductive parts, and leaves and stems). Only some biochemical fractions are useful to the biofuels industry, and because of this, shifts in biochemical stocks can have major economic impacts.
We present data from a corn agricultural ecosystem under four different agricultural scenarios: 1- unfertilized with a cover crop, 2- fertilized 202 kg N/ha with a cover crop, 3- unfertilized without a cover crop, and 4- fertilized 202 kg N/ha without a cover crop at the Kellogg Biological Station-Living Field Laboratory (KBS-LFL) in Michigan, USA in 2006. We measured the plant biochemical composition of the corn using 13C nuclear magnetic resonance spectroscopy (13C NMR) in combination with a molecular mixing model (Baldock et al., 2004).
We will discuss observed changes in biochemistry in each of the corn fractions and the implications of these changes for cellulosic ethanol production (leaves and stems fraction) as well as corn ethanol production (grain fraction). Increasing nitrogen fertilization rates always yields higher carbohydrate stocks, but the vast majority of the carbohydrate stock increase occurs as starch in the grain fraction. This implies that there is little value in nitrogen fertilization for crops grown for cellulosic ethanol.
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