Evaluation of the DNDC Model to Estimate Soil Parameters, Crop Yield and Nitrous Oxide Emissions for Alternative Long-Term Multi-Cropping Systems in the North China Plain

Optimizing crop rotations is one of the proposed sustainable management strategies for increasing carbon sequestration. The main aim of this study was to evaluate the DeNitrificationDeComposition (DNDC) model for estimating soil parameters (temperature, moisture and exchangeable NO₃⁻ and NH₄⁺), crop yield and nitrous oxide (N₂ O) emissions for long-term multi-cropping systems in Hebei, China. The model was validated using five years of data of soil parameters, crop yields and N₂ O emissions. The DNDC model effectively simulated daily soil temperature, cumulative soil nitrogen and crop yields of all crops. It predicted the trends of observed daily N₂ O emissions and their cumulative values well but overestimated the magnitude of some peaks. However, the model underestimated daily water filled pore space, especially in dry seasons, and had difficulties in correctly estimating daily exchangeable NO₃⁻ and NH₄⁺. Both observed and simulated cumulative N₂ O results showed that optimized and alternative cropping systems used less nitrogen fertiliser, increased grain yield and decreased N₂ O emissions compared to the conventional cropping system. Our study shows that although the DNDC model (v. 9.5) is not perfect in estimating daily N₂ O emissions for these long-term multi-cropping systems, it could still be an effective tool for predicting cumulative emissions.