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

Abstract

Abstract. Agricultural ecosystems are major sources of greenhouse gas (GHG) emissions, specifically nitrous oxide (N 2 O) and carbon dioxide (CO 2 ). An important method of investigating GHG emissions in agricultural ecosystems is model simulation. Field measurements quantifying N 2 O and CO 2 fluxes were taken in a summer maize ecosystem in Zhangye City, Gansu Province, in northwestern China in 2010. Observed N 2 O 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 2 O 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 2 O 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.

Assessing the impacts of tillage and fertilization management on nitrous oxide emissions in a cornfield using the DNDC model

“…In this study, the DNDC model indeed captured relatively lower peak emissions of N 2 O after fertilizer applications in the NT-manure than the NT-URAN management practice (Figures 3g-3i), while annual total cumulative N 2 O emissions did not significantly differ between them (Table 4). Considering the very low levels of SOC at our study sites (Table 2), this was probably because the manure amendment increased organic C input, which in turn provided more substrate to stimulate microbial activity and the production of N 2 O [Li et al, 2005;Wang et al, 2011]. Furthermore, with more and more organic C and N accumulation in the soil, the manure fertilizer might promote the emissions of N 2 O in the long term, as shown in the long-term (100 year) simulation ( Figure 5).…”

“…Seven variables, including mean annual temperature, total annual precipitation, SOC, pH, soil texture, and the amount of total N fertilizer application, were included for sensitivity test. A quantitative, relative sensitivity, referred to as the sensitivity index, was calculated to quantify the impacts of input factors on certain output results [Li et al, 1992b;Walker et al, 2000;Wang et al, 2011]:…”

“…(WFPS) [Dobbie and Smith, 2003;Q. Deng et al, 2015], availability of dissolvable organic carbon (DOC) [Li et al, 2005;Wang et al, 2011], and crop type, air/soil temperature and oxygen supply [Huang et al, 2014]. Therefore, N 2 O emissions in croplands are typically highly variable both in time and space.…”

Seasonal and Temporal Changes in Nitrous Oxide Emission with Fertilizer Application in Rice Ecosystem of North Bank Plain Agroclimatic Zone of North East India

“…In present study significant positive correlations of N 2 O emission with soil organic carbon (SOC) of the experimental fields is due to influence of SOC on denitrifying and nitrifying microorganisms. Since, nitrification is strongly influenced by CO 2 , while denitrification is driven by easily oxidizable C sources hence; both nitrification and denitrification are supported by the availability of C [23], [24]. Increased SOC at active vegetative growth stage in our study is attributed to availability of a large quantity of decomposable organic matter and carbon from root exudates with increasing root biomass of the plants.…”

The development of the DNDC plant growth sub-model and the application of DNDC in agriculture: A review

“…In regional mode, DNDC can be used to develop national inventories, assess the changes in greenhouse gas emissions in relation to the expected changes in management and climate, and verify mitigation strategies Li et al, 2002;Cai et al, 2003;Hastings et al, 2010;Wang et al, 2011).…”