我国作物生产碳排放特征及助力碳中和的减排固碳途径

Characteristics of carbon emission and approaches of carbon mitigation and sequestration for carbon neutrality in China’s crop production

作物生产不仅保障了国家粮食安全,也是农业碳排放的主要源,以及碳固定的重要汇。阐明主要农区作物生产碳排放特征,探讨其达峰与中和途径,可以为全国及地方作物生产绿色高质量发展和农业“双碳”目标的战略制定提供重要科学依据。本文基于国家统计数据,比较分析了我国各地区作物生产碳排放特征,探讨了助力碳中和的农田减排固碳途径。2018年我国作物生产碳排放占全国农业碳排放总量45.5%,其中农田甲烷(CH_(4))、氧化亚氮(N_(2)O)以及农用柴油消费的二氧化碳(CO_(2))排放分别占农业碳排放总量的22.9%、14.7%和7.9%。从区域排放来看,作物生产碳排放总量和单位播种面积排放量均呈现南高北低特征,其中以华东和华中地区最高,减排潜力大。在作物生产碳排放中,稻田CH_(4)占50.3%,是减排重点。我国作物生产碳排放总量于2015年出现峰值,之后呈现下降趋势,这与水稻播种面积、农田氮肥用量和农用柴油消费等减少趋势相一致。可见,如果我国农产品进口不受显著影响,作物生产碳排放已经呈现达峰趋势。情景推算发现,仅靠农地土壤固碳很难实现作物生产的碳中和,需要农田减排与固碳的兼顾。在丰产稳产前提下,作物生产碳中和要以稻田CH_(4)和旱地N_(2)O减排优先,在增强土壤碳汇功能的同时,充分挖掘秸秆资源化利用、用地养地结合和农田林网建设等农田生态系统的综合固碳潜力。

Crop production not only ensures national food security,but also is the main source of agricultural carbon emissions and an important pool of carbon sequestration.To clarify the characteristics of carbon emissions from crop production and discuss the approaches to reach the peak and neutrality in major agricultural areas can provide important scientific basis to the decision making of green and high-quality agricultural development and“dual-carbon”goal.Based on the national statistical data,this study compared and analyzed the characteristics of carbon emissions in crop planting regions in China,and presented the recommendations for carbon sequestration and greenhouse gas emission mitigation.The carbon emissions of crop production accounted for 45.5% of the national agricultural total carbon emissions in 2018,and the emissions of farmland methane(CH_(4)),nitrous oxide(N_(2)O),and carbon dioxide(CO_(2))of diesel consumption accounted for 22.9%,14.7%,and 7.9% of the total carbon emissions of agricultural production,respectively.In terms of the regional emissions,both the total carbon emission of crop production and the carbon emission per sowing area are higher in South than North China,with the highest emissions in East and central China and the greatest potential for emission mitigation.In the carbon emission from crop production,CH_(4) emission from rice fields accounts for the main part(50.3%)and is the focus of emission reduction.The annual carbon emission of crop production in China peaked in 2015,and then dropped down.It was mainly attributed to the decrease trend of rice sown area,agricultural nitrogen application rate,and diesel oil consumption.If the existing agricultural imports are not significantly affected,the carbon emissions in crop production have basically reached the peak.However,it is very difficult to achieve carbon neutrality in crop production if only by soil carbon sequestration of farmland,and it is necessary to consider both farmland emission reduction and carbon sequestration.On the premise of high and stable grain yield,the carbon neutrality of modern crop production should prioritize CH_(4) and N_(2)O reduction,and fully exploit the integrated carbon sequestration potential of farmland ecosystems,such as straw utilization,combination of the use and protection of farmland,and construction of farmland forest network.