Submitted to: Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 23, 2009
Publication Date: September 4, 2009
Repository URL: http://hdl.handle.net/10113/34926
Citation: Phillips, B.L., Podrebarac, F.A. 2009. Net Fluxes of CO2, but not N20 or CH4, are Affected Following Agronomic-Scale Additions of Urea to Prairie and Arable Soils. Soil Biology and Biochemistry. 41:2011-2013. Interpretive Summary: Granular urea is commonly used to fertilize crops in the Northern Great Plains and may affect soil gas emissions from arable cropland and prairie hayland ecosystems. We tested how different rate of N applied as urea affects emission of methane, nitrous oxide, and carbon dioxide for no-till cropland and native prairie. These three are known as greenhouse gases, and we aimed to determine if urea increased or decreased emissions. During short-term incubations, we found urea did not affect nitrous oxide or methane emissions. Urea did increase emissions of carbon dioxide for both the cropland and the prairie. As the rate of N applied increased, so did the rate of carbon dioxide emissions. At 112 kg N ha-1, CO2 production increased by a factor of four in cropland and by a factor of two in prairie soils. These results suggest addition of N as urea could increase mineralization of labile carbon in soils.
Technical Abstract: Microbial production of carbon dioxide (CO2) increased with nitrogen (N) application rate for both arable and prairie soils incubated at 21 °C. Rate of N applied as urea (0, 11, 56, 112 kg N ha-1) did not affect soil methane consumption and nitrous oxide production for soil collected from either ecosystem. Both arable and prairie soils responded to N addition with greater CO2 emissions, but the magnitude of this effect was greater for the arable soil. At 112 kg N ha-1, CO2 production increased by a factor of two for prairie soils and by a factor of four for arable soils. Urea fertilization induced a short-term increase in microbial C cycling for both prairie and arable soils. Nitrogen addition likely enhanced mineralization of readily decomposable carbon (C) substrates. Additional study is needed to determine effects of fertilization on more recalcitrant pools of soil C in northern prairie agricultural ecosystems.