秸秆还田下"麦-稻"轮作生产生命周期能耗及温室气体排放

应用生命周期评价方法,将"小麦-水稻"轮作生产体系生命周期划分为原料开采、农资生产和农田种植三个阶段,对秸秆不还田、全量还田、半量还田3种还田量下,生命周期各阶段的能源消耗与温室气体排放进行了清单分析,并进行了温室气体增温潜势评价。结果表明:以氮肥生产为主的农资生产阶段与原料开采阶段是能源消耗的主要阶段,占作物生产全生命周期能耗的70%左右;温室气体排放则以农田种植阶段为主。相较秸秆不还田处理,秸秆全量还田和半量还田增加了作物产量,降低了单位产品(分别为1 t小麦和1 t水稻)生产的CO2、N2O排放量,分别减排CO227.05%、31.23%,减排N2O 17.74%、14.51%,而CH4排放分别增加39.56%、12.38%;但在20 a、100 a时间尺度上,农田综合增温潜势GWP均显著降低。秸秆还田配合氮肥减施能有效降低农田生产系统生命周期能耗及温室气体增温潜势。

Life Cycle Energy Consumption and Greenhouse Gas Emissions of Wheat-Rice Rotation System with Straw Returning

In this study, we used life cycle inventory(LCI) to analyze the energy consumption and greenhouse gas emissions of wheat-rice rotation system with straw returning at each phase of the life cycle. Global warming potential(GWP) of this system was also evaluated. The life cycle of the wheat-rice rotation system was divided into three phases-raw material mining, agricultural supply production and crop growing. Three straw returning rates were designed:chemical fertilizer only(N1), chemical fertilizer plus whole rice straw returning(N1+S), and chemical fertilizer plus half rice straw returning(N1+0.5S). We found that agricultural supply production(nitrogen fertilizer production)and raw material mining accounted for nearly 70% of energy consumption of the whole life cycle, while cropland was the main source of GHG emissions. In N1+S and N1+0.5S treatments, crop yields increased by 14.31% and 15.46%, while CO₂ emission per tonne of yields decreased by 27.05% and 31.23%, and N₂O emission by 17.74% and 14.51%, but CH₄ emissions increased by 39.56% and 12.38%, respectively, compared with no straw returning. However, straw returning significantly decreased GWP on 20- and 100- year time scales. Our findings indicate that applications of straw and nitrogen fertilizer could help to reduce energy consumption and GWP in wheat-rice systems.