Modeling impacts of farming management practices on greenhouse gas emissions in the oasis region of China

Agricultural ecosystems are major sources of greenhouse gas (GHG) emissions, specifically nitrous oxide (N₂O) and carbon dioxide (CO₂). An important method of researching GHG emissions in agricultural ecosystems is model simulation. Field measurements quantifying N₂O and CO₂ fluxes were taken in a summer maize ecosystem in Zhangye City, Gansu Province, in northwestern China in 2010. Observed N₂O and CO₂ fluxes were used for validating flux predictions by a DeNitrification-DeComposition (DNDC) model. Then the validated DNDC model was used for sensitivity tests on three variables under consideration: climatic factors, soil properties, and agricultural management. Results indicate that: (1) the factors that N₂O emissions are most sensitive to nitrogen fertilizer application rate, manure amendment and residue return rate; (2) CO₂ emission increases with increasing manure amendment, residue return rate and initial soil organic carbon (SOC); and (3) net global warming potential (GWP) increases with increasing N fertilizer application rate and decreases as manure amendment, residue return rate and precipitation increase. Simulation of the long-term impact on SOC, N₂O and net GWP emissions over 100 yr of management led to the conclusion that increasing residue return rate is a more efficient method of mitigating GHG emission than increasing fertilizer N application rate in the study area