Agricultural ecosystems are major sources of greenhouse gas (GHG) emissions,specifically nitrous oxide (N2O) and carbon dioxide (CO2). Animportant method of investigating GHG emissions in agricultural ecosystemsis model simulation. Field measurements quantifying N2O and CO2 fluxes were taken in a summer maize ecosystem in Zhangye City, GansuProvince, in northwestern China in 2010. Observed N2O and CO2fluxes were used for validating flux predictions by aDeNitrification-DeComposition (DNDC) model. Then sensitivity tests on thevalidated DNDC model were carried out on three variables: climatic factors,soil properties and agricultural management. Results indicated that: (1) thefactors that N2O emissions were sensitive to included nitrogenfertilizer application rate, manure amendment and residue return rate; (2) CO2 emission increased with increasing manure amendment, residue returnrate and initial soil organic carbon (SOC); and (3) net global warmingpotential (GWP) increased with increasing N fertilizer application rate anddecreased with manure amendment, residue return rate and precipitationincrease. Simulation of the long-term impact on SOC, N2O and net GWPemissions over 100 yr of management led to the conclusion that increasingresidue return rate is a more efficient method of mitigating GHG emissionthan increasing fertilizer N application rate in the study area.
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