Rice is one of the most important food crops in China, and rice planting is a major contributor to the high level of CH4 and N2O emissions because of excessive application of nitrogenous fertilizers and basin irrigation. An important scientific and policy issue is how to balance the trade-off between food security concern and GHG emission reduction. In this research, the DeNitrification-DeComposition (DNDC) model  is employed to simulate the CH4 and N2O emissions from paddy fields in China. However, the default crop cultivar varieties in DNDC cannot represent the richness and regional diversity of cultivar varieties in China. A good approach to solving this problem is updating DNDC crop cultivar parameters by communicating with Decision Support System for Agrotechnology Transfer (DSSAT) and Agro-Ecological Zones (AEZ) for parameter calibration and validation, in a way similar to the DSSAT-AEZ coupling in . We then use the updated DNDC to evaluate plausible emission reduction choices under the condition of maintaining the prevailing attainable yield.
i) Coupling DNDC with DSSAT and AEZ for enriching and updating cultivar parameters in DNDC; ii) Up-scaling DNDC model with the assistance of the cropping zone classification method in AEZ.
Some key parameters, such as maximum potential yield and C/N ratio, that are calibrated and validated by DSSAT and AEZ based on observation data from nine agro-meteorological stations in China, were translated into the DNDC model. The DNDC simulation results show that the attainable yield without water stress and nitrogenous stress is more or less equal to the maximum observed yield, and the recorded nitrogenous fertilizer application is higher than the crop growth requirement by a scale of 5-35%, which leads to excessive N2O emission. A comparison between the recorded real fertilizer application and the optimum fertilizer scenario suggests a N2O emission reduction rate in the range of 9.1% - 68.3%.
i) The application of nitrogenous fertilizers is excessive in all nine case-study stations. ii) Reducing the application level of nitrogenous fertilizers to the optimum level will mitigate N2O emission without negative consequences for yield. iii) The relationship between CH4 emission and nitrogenous fertilizers is complex and obscure.
 Li C, Xiangming X, Frolking S, et al. (2003) Greenhouse Gas Emissions From Croplands of China. Quaternary Sciences, 23(5): 493-503.
 Tian Z, Zhong H, Sun L, et al, (2014). Improving Performance of Agro-ecological Zone (AEZ) Modeling by Cross-scale Model Coupling: An Application to Japonica Rice Production in Northeast China. Ecological Modeling, 290: 155-164.
Laixiang Sun, Water Program, IIASA
Lena Höglund lsaksson, Mitigation of Air Pollution and Greenhouse Gases Program, IIASA
Yilong Niu, of the Shanghai Institute of Technology and Climate Change, China, is a citizen of China. He was funded by the IIASA Chinese National Member Organization and worked in the Water Program during the YSSP.
Please note these Proceedings have received limited or no review from supervisors and IIASA program directors, and the views and results expressed therein do not necessarily represent IIASA, its National Member Organizations, or other organizations supporting the work.
Last edited: 08 February 2016
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