Simulation of N2O emissions from a sugarcane field in Okinawa, Japan

Abstract

We measured N2O emissions from a sugarcane field planted in spring 2011 in Okinawa, and examined their variations 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) models to estimate N2O emissions and compared the results with the observed data from the field experiment. The results showed that (i) nitrification was the dominant process affecting N2O emissions and 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 Greenhouse Gas Inventory of Japan; (iv) the DNDC model overestimated, and the APSIM model underestimated, the observed N2O emissions; and (v) simulation of N2O emissions associated with nitrification by the DNDC model might be improved by modifying coefficients in the equation used to calculate N2O production during nitrification.