Ruan, L. and G.P. Robertson
Presented at the All Scientist Meeting (2011-04-15 to 2011-04-15 )
Switchgrass, a native warm-season, perennial grass, has been evaluated one of the most promising bioful crops by the U.S Department of Energy. Cellulosic plants do not have high fertilizer requirements, but producers may apply more N fertilizer than minimum recommended levels especially if the price of biofuel crops yield is much higher than fertilizer cost. N input can directly increase soil N2O emissions, which offsets the effects of reducing Greenhouse gas (GHG) emissions of biofuels. Misunderstanding the relationship between nitrogen fertilizer application and N2O emissions will underestimate N2O emissions and thus contribution of soil N2O mitigation from using lower N fertilizer rate. Our objectives are to 1) study the response in soil N2O emissions to the input of N fertilizer in switchgrass; 2) study the relationship between N input and capabilities of soil CH4 oxidation. Eight treatments (0-196 kg N ha-1 nitrogen fertilization) established in spring, 2009 at the Great Lakes Bioenergy Research Consortium (GLBRC) site in southwestern Michigan. Plots are arranged in a randomized complete block design with four replications. In 2009, mean daily N2O emissions ranged between 1.86 g (N rate=0) and 10.3 g N ha-1d-1 (N rate=196 kg N ha-1) with maximum N2O fluxes of 152.9 g N ha-1d-1 in N rate=196 plots and minimum 0 N2O emissions in N rate=0 plots. The linear relationship between N input and cumulative N2O emissions was found in 2009 but exponential in 2010. The N2O fluxes were strongly correlated with precipitation. However, there is no significant difference of CH4 fluxes across different N rates.
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