Abstract:By using 15N techniques, effects of urea and KNO3 on processes of N2O production in Hydragric pad dy soil and Gleyic paddy soil, collected from Wuxi and Yingtan, respectively, were invest igated under flooding condit ions at 25.In the Hydragric paddy soil, N2 was a predominated product of denitrification process.Addition of KNO3 stimulated DNRA process and hence N2O product ion.In the Gleyic paddy soil, N2O was produced from denitrification and aerobic denitrification processes with its product ion rate increasing with soil pH and nitrate concentration.It was observed in some treatments of both the soils that the 15N abundance of N2O was larger than those of all the inorganic nitrogen, NH4+, NO3-, and NO2-, implying that the processes for N2O production would take place inside cells of microbes.