广西南宁市县域化肥施用碳足迹及其减排潜力

Carbon footprint and emission reduction potential of chemical fertilizer application at county scale in Nanning, Guangxi

【目的】分析广西南宁市县域的化肥碳足迹和碳减排潜力,为广西乃至全国制定差别化农业低碳政策和可行路径提供参考依据。【方法】基于生命周期理论,借鉴化肥碳足迹计算模型测算2005-2019年广西南宁市县域(武鸣区、隆安县、马山县、上林县、宾阳县和横州市)的化肥碳足迹和碳负荷,利用碳减排潜力模型分析科学施肥条件下广西南宁市县域的化肥碳减排潜力。【结果】广西南宁市县域的化肥碳足迹在2005-2019年间呈单峰变化,在2017年达峰值(74.54×10^(4)t CO_(2)eq),但2019年降至61.70×10^(4)t CO_(2)eq,下降17.23%,氮肥使用是化肥碳足迹增加的最主要原因;在6个县(区、市)中,武鸣区的化肥碳足迹最高,但土壤碳固存最大的区域也是武鸣区。2019年广西南宁市县域的化肥碳足迹普遍较低,平均为10.28×10^(4)t CO_(2)eq,但武鸣区、隆安县和宾阳县的化肥碳足迹较高,分别为31.48×10^(4)、9.26×10^(4)和9.82×10^(4)t CO_(2)eq。在土壤碳固存方面,武鸣区、横州市和宾阳县的土壤碳固存较大,分别为-8.43×10^(4)、-8.01×10^(4)和-7.08×10^(4)t CO_(2)eq;广西南宁市县域的平均化肥碳足迹强度(1.72 t CO_(2)eq/hm^(2))高于我国碳足迹负荷上限(1.22 t CO_(2)eq/hm^(2)),其中,武鸣区和隆安县的化肥碳足迹强度较高,分别为3.64和2.83 t CO_(2)eq/hm^(2),而马山县、上林县和横州市的化肥碳足迹强度(分别为0.64、1.09和0.73 t CO_(2)eq/hm^(2))处于中低水平。广西南宁市县域尺度的化肥施用碳足迹和碳足迹强度在空间上分布趋于一致,化肥碳足迹增加是由于碳足迹强度增加所致;从总体上看,广西南宁市县域的化肥碳减排潜力总计25.95×10^(4)t CO_(2)eq,其中,最高的是武鸣区,化肥减排潜力为20.21×10^(4)t CO_(2)eq,其次为隆安县和宾阳县,化肥碳减排潜力分别为4.49×10^(4)和1.25×10^(4)t CO_(2)eq,而马山县、上林县和横州市粮食种植的实际施肥水平基本达到农业农村部测土配方施肥技术给出的建议,无化肥碳减排潜力。【结论】广西南宁市县域的化肥碳足迹在2017年达到峰值,化肥施用碳足迹强度的增加是碳足迹增加的重要诱因;总体上广西南宁市县域的碳减排潜力较大。

【Objective】The present paper aimed to study the carbon footprint and carbon emission reduction potential of agricultural fertilizer at county scale in Nanning city,Guangxi province,so as to provide reference for Guangxi and the whole country to formulate differentiated agricultural low carbon policies and feasible paths.【Method】Based on the life cycle theory,the carbon footprint and carbon load of chemical fertilizers in Nanning county scale(Wuming district,Long’an county,Mashan county,Shanglin county,Binyang county and Hengzhou city)from 2005 to 2019 were calculated by referring to the calculation model of carbon footprint of chemical fertilizers.The carbon emission reduction potential model was used to analyze the carbon emission reduction potential of chemical fertilizers in Nanning county scale under the condition of scientific fertilization.【Result】The chemical fertilizer carbon footprint of Nanning city(city,district)showed a single peak change from 2005 to 2019,and reached its peak in 2017(74.54×10^(4)t CO_(2)eq),but decreased to 61.70×10^(4)t CO_(2)eq in 2019,with a decrease of 17.23%.The use of nitrogen fertilizer was the main reason for the increase of chemical fertilizer carbon footprint.The fertilizer carbon footprint in Wuming district was the highest,but the area with the largest soil carbon sequestration was also Wuming district.In 2019,the carbon footprint of fertilizer in Nanning(city,district)was generally low,with an average of 10.28×10^(4)t CO_(2)eq.However,the carbon footprint of fertilizer in Wuming district,Long’an county and binyang county was high,with 31.48×10^(4),9.26×10^(4)and 9.82×10^(4)t CO_(2)eq,respectively.In terms of soil carbon sequestration,Wuming district,Hengzhou city and Binyang county had relatively large soil carbon sequestration,which were-8.43×10^(4),-8.01×10^(4)and-7.08×10^(4)t CO_(2)eq,respectively.The areas with higher chemical fertilizer carbon footprint intensity were Wuming district and Long’an county,3.64 and 2.83 t CO_(2)eq/hm^(2),respectively.The carbon footprint intensity of fertilizer in Mashan county(0.64 t CO_(2)eq/hm^(2)),Shanglin county(1.09 t CO_(2)eq/hm^(2))and Hengzhou city(0.73 t CO_(2)eq/hm^(2))was at a medium and low level,but the average carbon footprint intensity of fertilizer(1.72 t CO_(2)eq/hm^(2))was higher than the upper limit of carbon footprint load in China(1.22 t CO_(2)eq/hm^(2)).The spatial distribution of chemical fertilizer carbon footprint and carbon footprint intensity tends to be consistent.The increase of chemical fertilizer carbon footprint at county scale in Nanning city was due to the increase of carbon footprint intensity.Overall,the total potential of chemical fertilizer carbon emission reduction in Nanning city(city,district)was 25.95×10^(4)t CO_(2)eq,the highest was Wuming district,the potential of chemical fertilizer carbon emission reduction was 20.21×10^(4)t CO_(2)eq,followed by Long’an county and Binyang county,the potential of chemical fertilizer carbon emission reduction was 4.49×10^(4)and 1.25×10^(4)t CO_(2)eq,respectively.The actual fertilization levels of grain planting in Mashan county,Shanglin county and Hengzhou city basically reached the suggestions given by the soil testing and formulated fertilization technology of the Ministry of Agriculture and Rural Affairs,and there was no potential for carbon emission reduction of chemical fertilizers.【Conclusion】The carbon footprint of chemical fertilizers in Nanning reached its peak in 2017.The increase of carbon footprint intensity of chemical fertilizers was an important incentive for the increase of carbon footprint.In general,the carbon emission reduction potential of counties(cities,districts)in Nanning,Guangxi was large.