Study on the difference of rice-wheat rotation system greenhouse gas estimation by different simulation methods

Global warming, mainly caused by greenhouse gas (GHG) emissions, is one of the major concerns of the current society. Accurate estimation of GHG emissions in various fields can help governments and international organizations to formulate emission reduction strategies.The main objectives of this study were to estimate CH4 and N2O emissions from rice-wheat crop fields using IPCC2006 Tier2 approach and DNDC model, and to compare the performance of the two methods; and to evaluate the accuracy of GHG emissions of the DNDC model with rotational and non-rotational simulation scenarios. In this study, we conducted a rice-wheat rotational field experiment from 2015 to 2018 to determine CH4 and N2O fluxes periodically using static chamber-gas chromatography measurement and analysis system. On this basis, combined with field management and meteorological data, we simulated GHG emissions from rotational and non-rotational crop scenarios using the IPCC2006 Tier2 approach and the DNDC model. The results show that (1) the DNDC model can simulate the time series of paddy CH4 and N2O emission fluxes and winter wheat N2O emission fluxes with estimation errors of -4.8%, -11.6%, and -10.8%, respectively, and the modeling accuracy is better than that of the IPCC2006 Tier2 approach; (2) the accuracy of the DNDC model for simulating the GWP under the rotational cropping scenarios was higher than that of the IPCC2006 Tier2 approach, the relative errors of GWP simulation in the DNDC model were -5.9% and -21.7% for rice and wheat fields, respectively; (3) the relative errors of winter wheat cumulative CH4 emissions in the rotational cropping scenario in the DNDC model were higher than those in the non-rotational cropping scenario, and the relative errors of cumulative emissions of other GHGs in the rotational cropping scenario were lower than those in the non-rotational cropping scenario.This study provides some references for estimating regional agricultural GHG emissions and formulating emission reduction targets and policies.Keywords: Rice-wheat rotation; DNDC; IPCC2006 Tier2; Greenhouse gases