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

Abstract. Agricultural ecosystems are major sources of greenhouse gas (GHG) emissions, specifically nitrous oxide (N₂O) and carbon dioxide (CO₂). An important method of investigating 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 sensitivity tests on the validated DNDC model were carried out on three variables: climatic factors, soil properties and agricultural management. Results indicated that: (1) the factors that N₂O emissions were sensitive to included nitrogen fertilizer application rate, manure amendment and residue return rate; (2) CO₂ emission increased with increasing manure amendment, residue return rate and initial soil organic carbon (SOC); and (3) net global warming potential (GWP) increased with increasing N fertilizer application rate and decreased with 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.