Effects of the Applied Amount of Wheat Straw on Methane, Carbon Dioxide, Nitrous Oxide, and Nitric Oxide Fluxes of a Bare Soil in South Shanxi

Using manual static opaque chamber/gas chromatograph and chemiluminescence measuring systems, the authors monitored the fluxes of methane (CH₄), carbon dioxide (CO₂), nitrous oxide (N₂O), and nitric oxide (NO) from the bare soil of a wheat-maize rotation field applied with different amounts of wheat straw in south Shanxi from 20 June to 6 October 2008. During the measuring period, the mean fluxes of CH₄, CO₂, N₂O, and NO were -0.8±2.7, -1.4±2.3, and -6.5±1.8 μg (C)·m^-2·h^-1 (CH₄), 267.1±23.1, 212.0±17.8, and 188.5±13.6 mg (C)·m^-2·h^-1 (CO₂), 20.7±3.0, 16.3±2.3, and 14.7±1.7 μg (N) ·m^-2·h^-1 (N₂O), and 3.9±0.5, 3.4±0.5, and 3.0±0.4 μg (N) ·m^-2·h^-1 (NO), respectively, at the full straw-amended (FS), half straw-amended (HS), and no straw-amended (NS) treatments. The fluxes presented significantly seasonal fluctuations, which were mainly regulated by the irrigation, precipitation, and variation of soil temperature. Compared with NS, FS and HS reduced the accumulative absorption of CH₄ (66% and 59%), and increased the accumulative emissions of CO₂ (42% and 12%), N₂O (41% and 9%), and NO (30% and 13%). The straw-amended treatments enhanced the total greenhouse gas emissions from the agricultural soil. The calculated CO₂, N₂O, and NO emission factors of applied wheat straw at FS and HS were 73.4%±1.6% and 43.3%±1.0% (CO₂), 0.37%±0.01% and 0.17%±0.00% (N₂O), and 0.06%±0.00% and 0.05%±0.00% (NO), respectively. The emission factors at FS were significantly higher than at HS. The emission factors at FS and HS were much lower than that (emission factors of N₂O and NO were 2.32% and 0.42%, respectively) for the same field with chemical fertilization and maize growing. Therefore, the effects of the applied amounts of crop straw, fertilization, and crop growing should be taken into account in the estimation of CO₂, N₂O, and NO emissions induced by crop straw based on emission factor methodology.