Using the SMART-Farm Tool to identify linchpin farming practices for the improvement of the atmosphere-related sustainability performance of the Luxembourgish agriculture sector.

Agriculture is a major source of environmental emissions, including greenhouse gases (GHG), ammonia and other air pollutant emissions, particularly in livestock-intensive countries such as Luxembourg. Organic agriculture has attracted attention as a more environmentally friendly agricultural management system. This study assessed the atmosphere-related sustainability performance of 87 farms (4.5 % of all farms in Luxembourg) using the Sustainability Monitoring and Assessment RouTine (SMART)-Farm Tool, which operationalizes the Food and Agriculture Organisation of the United Nations (FAO)'s Sustainability Assessment of Food and Agriculture Systems (SAFA) Guidelines. The sample included 58 conventional and 29 organic farms. Results showed that organically managed farms (orgF) achieved significantly higher sustainability scores than conventional farms (conF) in the Atmosphere theme (orgF mean: 63.8 %, conF mean: 56.6 %, p < 0.001), as well as in the sub-themes Air Quality (orgF mean: 69.3 %, conF mean: 59.1 %, p < 0.001) and Greenhouse Gases (orgF mean: 57.7 %, conF mean: 53.5 %, p = 0.002). Indicator-level analysis identified two key improvement strategies: (1) increasing concentrated feed autarky, with organic farms relying less on external protein and energy feeds; and (2) closing nutrient cycles, evidenced by higher use of legumes, green cover, and lower nitrogen inputs. These practices were strongly associated with improved atmospheric sustainability performance. Additionally, practices such as reduced tillage and cover cropping were underutilized across all systems, indicating broader areas for optimisation. While organic management outperformed conventional, the findings emphasize that many beneficial practices can be adopted system-independently. Policy efforts should focus on supporting these two linchpin strategies to trigger the development of a more sustainable farming system in Luxembourg and increase the sector's atmosphere-related sustainability performance.