"Climate-smart” crop cultivation, characterized by a low greenhouse gas (GHG) footprint, low synthetic nitrogen consumption, and simultaneously high yields (Figure 1), is an approach in agriculture for implementing the Paris Agreement as part of mitigating climate change. The GHG footprint is an index used to indicate the climate change impact potential exerted by crop production. It is therefore crucial to accurately quantify the GHG footprints of crop cultivation systems. However, severe problems or drawbacks in the quantification of GHG footprints still exist, which has limited the applicability of the GHG footprint in crop cultivation.