小麦秸秆还田量对晋南地区裸地土壤—大气间甲烷、二氧化碳、氧化亚氮和一氧化氮交换的影响

采用静态暗箱采样—气相色谱/化学发光分析相结合的方法,对晋南地区盐碱地不同小麦秸秆还田量裸地土壤夏、秋季(2008年6～10月)的甲烷(CH4)、二氧化碳(CO2)、氧化亚氮(N2O)和一氧化氮(NO)交换通量进行了原位观测。结果表明:观测期内,秸秆全还田(FS)、秸秆一半还田(HS)和秸秆不还田(NS)处理土壤—大气间CH4、CO2、N2O和NO平均交换通量分别为-0.8±2.7、-1.4±2.3、-6.5±1.8μg(C).m-2.h-1(CH4),267.1±23.1、212.0±17.8、188.5±13.6mg(C).m-2.h-1(CO2),20.7±3.0、16.3±2.3、14.7±1.7μg(N).m-2.h-1(N2O),3.9±0.5、3.4±0.5、3.0±0.4μg(N).m-2.h-1(NO)。交换通量表现出明显的季节变化趋势,灌溉、降雨和温度变化是影响该趋势的主要因素。相对于NS处理,FS和HS处理降低了累积CH4吸收量(66%和59%),增加了累积CO2(42%和12%)、N2O(41%和9%)和NO(30%和13%)排放量,因此,秸秆还田促进了农田土壤总的温室气体排放。计算得到FS和HS处理小麦秸秆的CO2、N2O、NO排放系数分别为73.4%±1.6%和43.3%±1.0%(CO2)、0.37%±0.01%和0.17%±0.00%(N2O)、0.06%±0.00%和0.05%±0.00%(NO),FS处理的排放系数显著高于HS处理,且均低于同一实验地种植玉米、施肥农田的小麦秸秆排放系数(N2O和NO排放系数分别为2.32%和0.42%)。可见,在采用排放因子方法估算还田秸秆CO2、N2O和NO排放量时,应考虑秸秆还田量、农作物种植和施肥因素的影响。

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(CH 4),carbon dioxide(CO 2),nitrous oxide(N 2 O),and nitric oxide(NO) fromthe 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 CH 4,CO 2,N 2 O,and NO were-0.8±2.7,-1.4±2.3,and-6.5±1.8 μg(C).m-2.h-1(CH 4),267.1±23.1,212.0±17.8,and 188.5±13.6 mg(C).m-2.h-1(CO 2),20.7±3.0,16.3±2.3,and 14.7±1.7 μg(N).m-2.h-1(N 2 O),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 CH 4(66% and 59%),and increased the accumulative emissions of CO 2(42% and 12%),N 2 O(41% and 9%),and NO(30% and 13%).The straw-amended treatments enhanced the total greenhouse gas emissions from the agricultural soil.The calculated CO 2,N 2 O,and NO emission factors of applied wheat straw at FS and HS were 73.4%±1.6% and 43.3%±1.0%(CO 2),0.37%±0.01% and 0.17%±0.00%(N 2 O),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 N 2 O 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 CO 2,N 2 O,and NO emissions induced by crop straw based on emission factor methodology.