N2O Emissions from Two Austrian Agricultural Catchments Simulated with an N2O Submodule Developed for the SWAT Model

Abstract

Nitrous oxide (N2O) is a potent greenhouse gas stemming mainly from nitrogen (N)-fertilizer application. It is challenging to quantify N2O emissions from agroecosystems because of the dearth of measured data and high spatial variability of the emissions. The eco-hydrological model SWAT (Soil and Water Assessment Tool) simulates hydrological processes and N fluxes in a catchment. However, the routine for simulating N2O emissions is still missing in the SWAT model. A submodule was developed based on the outputs of the SWAT model to partition N2O from the simulated nitrification by applying a coefficient (K2) and also to isolate N2O from the simulated denitrification (N2O + N2) with a modified semi-empirical equation. The submodule was applied to quantify N2O emissions and N2O emission factors from selected crops in two agricultural catchments by using NH4NO3 fertilizer and the combination of organic N and NO3− fertilizer as N input data. The setup with the combination of organic N and NO3− fertilizer simulated lower N2O emissions than the setup with NH4NO3 fertilizer. When the water balance was simulated well (absolute percentage error <11%), the impact of N fertilizer application on the simulated N2O emissions was captured. More research to test the submodule with measured data is needed.

N2O Emissions from Aquatic Ecosystems: A Review

“…The Bern3D Earth system model calculates N 2 O emissions based on denitrification and organic matter consumption and estimates an oceanic N 2 O budget of 4.5 ± 1.0 Tg N yr −1 [25]. Process-based models show good advantages to estimate aquatic N 2 O emissions in the absence of measured data and to predict the response of N 2 O fluxes to multifactor climate and environmental changes [25,79,121,122]. In addition, the process-based N 2 O emission model can be integrated with hydrological models to predict changes in N 2 O emissions in response to land use changes beside the water bodies [37,118,123].…”