Source partitioning and emission factor of nitrous oxide during warm and cold cropping seasons from an upland soil in South Korea

Abstract Nitrous oxide (N 2 O) is a major greenhouse gas (GHG) with high global warming potential. A majority of the N 2 O flux comes from agricultural sources, mainly due to nitrogen (N) fertilization. The soil N 2 O flux, induced by N fertilization, mainly originated from two different sources, i.e., fertilizer and soil organic nitrogen (SON). It is essential to know the individual contribution of these two different sources in total N 2 O flux for planning necessary mitigation strategies. It is also indispensable to know the seasonal difference of emission factors (EF) for having more accurate N 2 O inventory. Therefore, an experiment was conducted in a South Korean upland soil during summer and winter seasons using 15 N labeled urea as an artificial N source and source specific N 2 O emissions were distinguished under different environmental conditions. To characterize the N 2 O emissions from urea, 0, 50, 100 and 200% of the Korean N recommendation rate was selected for specified crops. The Korean N recommendation rate for red pepper ( Capsicum annuum ) and garlic ( Allium sativum ) was 190 and 250 kg N ha −1 , respectively. Direct emissions from urea were estimated from the difference of 15 N 2 O flux emitted from 15 N-urea treated soil and the natural abundance of 15 N 2 O. From total N 2 O fluxes, urea originated N 2 O flux was 0.87% and 0.13% of the applied N in warm and cold seasons, respectively and the rest comes from SON. Nitrous oxide EF in the warm season was 2.69% of applied N and in the cold season that was 0.25%. Nitrous oxide fluxes showed a significant exponential relationship with soil temperature. The results show the necessity of considering the different N 2 O EF for warm and cold cropping seasons to reduce uncertainty in N 2 O inventory. The findings of this research may help better understand N 2 O source partitioning and the emission budget from warm and cold cropping seasons.