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

Cong Wang,Gernot Bodner,Ottavia Zoboli,Matthias Zessner,Andrea Watzinger,Karsten Schulz,Christoph Schürz,Bano Mehdi-Schulz

doi:10.3390/atmos13010050

Cong Wang, Gernot Bodner + Show 6 more

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https://doi.org/10.3390/atmos13010050

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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.

Highlights

Nitrous oxide (N2O) is a potent greenhouse gas (GHG) that contributes to global warming and mainly stems from agricultural soils [1]
We develop an N2O submodule based on the eco-hydrological SWAT model outputs to quantify the integrated N2O emissions and N2O emission factor (EF) from two agricultural catchments (Melk and Zaya) with two N fertilizer regimes
The reasons are (1) more than 35 kg ha−1 N fertilizer was applied to the grain corn in the M1 setup, which contributes to more N2O emissions (Table 3, Figure 8). (2) The dates of N fertilizer application in the M1 setup were split according to different crop growing stages (Figure 7), which influenced the efficiency of fertilizer use and N2O emissions [66]

Summary

Introduction

Nitrous oxide (N2O) is a potent greenhouse gas (GHG) that contributes to global warming and mainly stems from agricultural soils [1]. To estimate the amount of N2O emitted from an agricultural field in the absence of measured data, the Intergovernmental Panel on Climate Change (IPCC) recommends estimating the N2O emissions as a fraction of the N input to the soil. This is known as the N2O emission factor (EF), which is defined as kg N2O-N kg−1 N input [3,4,5]. Calculating the EF for N2O was based on a simple regression model established by Bouwman [6] who estimated the contribution of fertilizers encompassed 90% of the total N2O emissions. An EF for N2O of 1.25 ± 1.0% of the applied N fertilizer amount was adopted in 1996 [3,8]

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