An automated system for continuous measurement of N 2 O fluxes on an hourly basis was employed to study N 2 O emissions in an intensively managed low carbon calcareous soil under sub-humid temperate monsoon conditions. N 2 O emissions occurred mainly within two weeks of application of NH 4 + -based fertilizer and total N 2 O emissions in wheat (average 0.35 or 0.21 kg N ha −1 season −1 ) and maize (average 1.47 or 0.49 kg N ha −1 season −1 ) under conventional and optimum N fertilization (300 and 50–122 kg N ha −1 , respectively) were lower than previously reported from low frequency measurements. Results from closed static chamber showed that N 2 O was produced mainly from nitrification of NH 4 + -based fertilizer, with little denitrification occurring due to limited readily oxidizable carbon and low soil moisture despite consistently high soil nitrate-N concentrations. Significant reductions in N 2 O emissions can be achieved by optimizing fertilizer N rates, using nitrification inhibitors, or changing from NH 4 + - to NO 3 ˉ -based fertilizers.