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

摘要

Agricultural ecosystems are major sources of greenhouse gas (GHG) emissions, specifically nitrous ox-ide (N_2O) and carbon dioxide (CO_2). An important method of investigating GHG emissions in agricultural ecosystems is model simulation. Field measurements quantifying N_2O and CO_2 fluxes were taken in a summer maize ecosystem in Zhangye City, Gansu Province, in northwestern China in 2010. Observed N_2O and CO_2 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 N_2O emissions were sensitive to included nitrogen fertilizer application rate, manure amendment and residue return rate; (2) CO_2 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, N_2O 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.