Transcript Slide 1
N2O-It’s No Laughing Matter! Leilei Ruan and Sandy Erwin Introduction Surface temperature has increased to 0.74 oC from 1906 to 2005 and are expected to rise to 1.1-6.4 oC by 2100. The increases of greenhouse gas (CO2, CH4 and N2O) since 1750 are dramatic compared with antecedent concentrations CO2 concentration 280 ppm CH4 715 ppb 1774 ppb N2O 270 ppb 319 ppb 379 ppm Biofuels Question: can biofuels really mitigate Greenhouse gas (GHG) emissions? Question: can biofuels really mitigate Greenhouse gas (GHG) emissions? Biofuels are not 100% “GHG neutral” due to cultivation Soil CO2 will release when soil carbon is oxidized following cultivation CH4 oxidation is reduced N2O is released Concentratio Global warming potential by time n horizon 20 years 100 years 500 years CO2 379 ppm 1 1 1 CH4 1774 ppb 72 25 7.6 N 2O 319 ppb 289 298 153 Nitrogen cycle N2 N2 NOx, N2O NOx, N2O Nitrogen in animals and microbes Nitrogen back to soil Nitrogen in plants + NH4+ NO3denitrification nitrification Bacteria fix N2 6 Extra source for nitrogen cycle: http://youtu.be/6GLIzlUD-zw Soil Safari : http://school.discoveryeducation.com/schoolad ventures/soil/down_dirty.html www.glbrc.org The impacts of nitrogen fertilizer management on GHG emissions in switchgrass Hypothesis: The response in soil N2O emissions to the inputs of N fertilizer in switchgrass will be non-linear; in particular, fluxes will increase sharply after biomass yields no longer increase. Total N2O emissions Conceptual model IPCC linear response N fertilizer applied Objective 1 : To determine the Impacts of nitrogen fertilizer management on GHG emissions in switchgrass Hypothesis: The response in soil N2O emissions to the inputs of N fertilizer in switchgrass will be non-linear; in particular, fluxes will increase sharply after biomass yields no longer increase. Total N2O emissions Conceptual model Hypothesized non-linear response maximum plant demand IPCC linear response N fertilizer applied Experimental design http://lter.kbs.msu.edu/photos/index.php 4.75m 140 56 196 112 84 168 0 28 196 168 140 Block 1 112 56 Block 2 84 28 196 Block 3 112 84 56 28 0 Block 2 168 140 0 0 56 Block 1 168 112 196 Block 4 15m 10m 28 140 84 N-Rate( kg ha-1) Experimental materials and methods Static Chamber - 4 samples taken during an hour-long closure. Gas Chromatograph: N2O (ECD) (CV=2.4%), CH4 (FID), and CO2 (IRGA) analysis 13 Field time www.glbrc.org 14 Data nugget and discussion www.glbrc.org Biomass yield in Switchgrass during 2009 5 d c c 56 84 cd cd cd -1 Biomass yield (Mg ha ) 4 b 3 a 2 1 0 0 28 112 140 168 196 -1 N rate( kg N ha ) Biomass yield in Switchgrass during 2010 12 c -1 Biomass yield (Mg ha ) 10 8 bc bc ab bc bc bc 140 168 196 a 6 4 2 0 0 28 56 84 112 -1 N rate( kg N ha )