The use of N fertilizers for agricultural production acts as a sources of atmospheric . Fertilizer induced emission considerably varies in accordance with environmental factors. We conducted a flux measurement campaign across 10 different experimental sites with various soil types throughout Japan and investigated the fertilizer induced emission factors (FIEFs) of synthetic fertilizers (mainly urea) in multiple growing periods at each experimental site. FIEFs considerably varied among the 10 sites, and measurement periods ranged from 0.00 to 7.13 % in 40 total observations. Soil profile information divided the experimental sites into two major groups through cluster analysis, which are volcanic or non-volcanic soils. According to this classification, FIEFs were clearly differentiated into high and low FIEF groups (mean values: 2.67 and 0.59 %, respectively). Regression trees selected total soil carbon, the depth to the Fe mottling horizon, and mean air temperature as the key parameters to determine the strength of FIEFs out of 10 explanatory variables (e.g., N fertilizer application rates, fertilizer application times, clay content, total precipitation during measurement periods, pH, total soil carbon, and total soil nitrogen). The existence of shallow Fe mottling layer (up to 42.5 cm) induced high FIEFs in this model, suggesting that upward emissions derived from the intermediate Fe mottling layers presumably contributed high emissions in such soils. Our results suggest that the soil profile information associated with the water regime is an important index for synthetic fertilizer induced emissions.
