不同耕作措施对雨养冬小麦碳足迹的影响

为了解不同耕作管理措施对我国北方旱作农田作物生产生命周期内生产资料及生产过程碳排放足迹的影响,在山西省临汾市尧都区连续15年保护性耕作长期定位试验基地,利用静态箱-气相色谱法连续两年测定了不同秸秆管理和耕作措施(秸秆不还田旋耕、秸秆还田旋耕、秸秆覆盖免耕)下,旱作冬小麦田N_2O周年排放通量,并对不同耕作管理措施的生产资料和生产过程中的碳排放进行全面分析与计算,以估算不同耕作措施的碳足迹。结果表明:1)秸秆覆盖免耕和秸秆不还田旋耕条件下旱作冬小麦田N_2O年度累积排放量较秸秆还田旋耕分别平均减少19.2%和18.9%;2)旱作冬小麦在秸秆覆盖免耕条件下产量最高;3)旱作农田碳足迹中氮肥生产、农田N_2O直接排放和柴油消耗排放占到总排放足迹的90%以上;4)秸秆覆盖免耕较其他耕作方式的碳足迹低,两年试验期间,较秸秆还田旋耕处理碳足迹分别低11.0%和6.9%,较秸秆不还田旋耕处理碳足迹分别低7.9%和8.3%。5)在半干旱地区,秸秆覆盖免耕处理单位产量碳足迹最低,是本研究中低碳低排的推荐措施。本研究结果可为旱作农田以低碳减排为目标的可持续发展提供科学依据。

Effect of tillage practice on carbon footprint of rainfed winter wheat

It is crucial to mitigate greenhouse gas emissions from soil and to abate carbon emissions from the production of goods (e.g., fertilizers, seeds, etc.) and production processes (e.g., diesel consumption by machines) for sustainable agricultural production. In order to evaluate carbon footprint and carbon emission intensity of different tillage practices in rainfed field, a 15-year long-term experiment with three different tillage practices was conducted in Linfen, Shanxi Province, a typical semi-arid area in North China. The investigated tillage management practices were rotary tillage without straw incorporation (RT), straw incorporation and rotary tillage (SRT) and straw-mulch and no-tillage (SNT). Carbon footprint in the production life-cycle of different tillage practice of rainfed winter wheat was explored, in which N₂O emissions from field were measured using the static chamber-gas chromatography method and the other emissions calculated by analyzing emissions from the production of main goods and the associated processes during life-cycle period of winter wheat. The results showed that N₂O emissions under SNT and RT management practices were 19.2% and 18.9% lower than that under SRT practice, respectively. N₂O emissions mainly occurred during the period from booting to maturity and then the period of summer fallow when soil temperature and moisture were most appropriate. N₂O emissions derived directly from nitrogen fertilizer and carbon emissions from the processes of chemical fertilizer production explained the most share of carbon footprint in the life-cycle of rainfed winter wheat, accounting for 21.6% and 46.4% of the total carbon footprints, respectively. N₂O emissions and carbon emissions derived from nitrogen fertilizer production and diesel consumption, and direct emission for field accounted for over 90% of the carbon footprint of rainfed winter wheat system. Carbon footprint under SNT practice was the lowest among three treatments, it was respectively 7.9%-11.0% and 6.9%-8.3% lower than those under SRT and RT. SNT management practice had the lowest carbon footprint among three tillage practices. Thus, straw incorporation with no-tillage was the most appropriate practice for sustainable agricultural production aimed at low greenhouse gas emissions and low carbon consumption in the semi-arid area of North China.