We measuredN2O emissions from a sugarcane field planted in spring 2011 in Okinawa,and examined theirvariations during the summer growing period (13 July to 4 August).Then we performed simulations with the DeNitrification and DeComposition(DNDC)and Agricultural Production Systems Simulator(APSIM)modelsto estimate N2O emissionsand compared the results with the observed data from the field experiment.Theresults showedthat (i) nitrification was the dominantprocessaffecting N2O emissionsand nitrifier denitrification occurred under high soil moisture conditions after rainfall;(ii) there was large spatial dispersion of N2O emissions even in the same field,and it was necessary to consider this dispersion to estimate total N2O emissions from the field; (iii) the emission factor of the N2O emissions might be larger than that used by the National GreenhouseGas Inventory of Japan;(iv) the DNDC model overestimated,and the APSIM model underestimated,the observed N2O emissions; and(v) simulation of N2O emissions associated withnitrificationby the DNDC model might be improved by modifyingcoefficients in the equationusedto calculate N2O production during nitrification.