Greenhouse gas emission characteristics and influencing factors of the crop and livestock production systems, Shanxi Province

Analysis of the spatial and temporal distribution characteristics of carbon emissions in the crop and livestock production systems in Shanxi Province, and clarifying the main factors influencing these systems are key to promoting the green development of crop and livestock production systems in Shanxi Province, and this provide a foundation for the development of organic dry farming in Shanxi Province. Herein, we collected crop and livestock production data at county level in Shanxi Province in 1985 and 2018, and used the life cycle assessment method combined with the latest greenhouse gas (GHG) inventory guidelines to compile a GHG emission inventory for the crop and livestock production systems. In addition, we used GIS to characterize the spatial and temporal distribution characteristics of GHG emissions in the crop and livestock production systems at county scale. We also examined the intensity of GHG emissions based on unit cultivated land area and unit energy in crop and livestock products, and accordingly identified GHG emission hotspots. Furthermore, the main influencing factors in different years were quantified based on random forest analysis. The results revealed that from 1985 to 2018, total GHG emissions from the crop and livestock production systems in Shanxi Province increased from 17.42 to 20.75 million t(CO₂ eq), representing an increase of 19.10%. The agricultural input for the crop system in different years were the main contributors to GHG emissions within the overall crop and livestock production systems, accounting for 41.08%−54.23% of the total emissions. We found that the production of GHG by burning straw decreased from 4.44 million t(CO₂ eq) in 1985 to 3.21 million t(CO₂ eq) in 2018, with the total emissions proportion decreasing from 25.46% to 15.47%, which was the second largest GHG emission source in the entire crop and livestcok prodcution system. Contrastingly, GHG emissions from soil increased from 1.51 to 2.32 million t(CO₂ eq), with the total emissions proportion increasing from 8.68% to 11.18%. Similarly, we detected a 2.30 fold increase in the GHG emissions derived from animal enteric fermentation and manure management system in the livestock production system, from 2.03 to 6.69 million t(CO₂ eq), with the proportion of total emissions increasing from 11.64% to 32.23%. With respect to the entire crop and livestock production systems, the intensity of GHG emissions increased from 4.63 to 5.12 t·hm⁻², although we detected a significant reduction in the GHG emissions per energy in crop and livestock products from 0.15 to 0.08 kg(CO₂ eq)·MJ⁻¹. Furthermore, the results of random forest analysis revealed that nitrogen fertilizer application and planting structure were the main factors influencing GHG emission intensity and efficiency, although the nature of the influencing factors was found to differ in different years. The optimal management of nitrogen fertilization and improvements in crop structure and animal husbandry management were identified as key factors for reducing GHG emissions. Our findings in this study will provide a valuable reference for understanding and enhancing the green development of crop and livestock production systems.