COS 21-7 - The impact of N fertilizer management on nitrous oxide and methane fluxes in switchgrass

Tuesday, August 9, 2011: 10:10 AM
6A, Austin Convention Center
Leilei Ruan, W.K Kellogg Biological Station & Crop and Soil Sciences, Michigan State University, Hickory Corners, MI and G. Philip Robertson, Plant, Soil, and Microbial Sciences and W. K. Kellogg Biological Station, Michigan State University, Hickory Corners, MI

Switchgrass, a native warm-season, perennial grass, has been identified as one of the most promising cellulosic biofuel crops. Perennial cellulosic crops 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 costs. N input can directly increase soil N2O emissions, which offsets the effects of reduced greenhouse gas (GHG) emissions of biofuels. The uncertainties about the magnitude of N2O emissions can be magnified by its high global warming potential. N fertilizer can also offset the positive effects of any increased methane (CH4) oxidation in switchgrass. We studied the response in soil N2O emissions to the input of N fertilizer in switchgrass and the relationship between N input and potentials for soil CH4 oxidation. Eight fertilizer levels (0-196 kg N ha-1) were applied to replicate field plots established in spring, 2009, at the Great Lakes Bioenergy Research Center (GLBRC) site at the Kellogg Biological Station in southwest 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 a maximum daily N2O flux of 152.9 g N ha-1d-1 in the highest N rate  plots and a minimum daily flux of nil in  plots that received no fertilizer N. A linear relationship between N input and cumulative N2O emissions was found for the establishment year. N2O fluxes were strongly correlated with precipitation. We found uniformly low CH4 fluxes across the different N rates

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