Application of the DNDC model to predict emissions of N2O from Irish agriculture

Abstract

Models are increasingly used to examine the potential impacts of management and climate change in agriculture. Our aim in this paper was to assess the applicability of the field-DeNitrification DeComposition (DNDC) model in Irish agriculture. This study provides the results of that evaluation, which is a prerequisite for using the model for assessing management impacts in the future. The DNDC model was tested against seasonal and annual data sets of nitrous oxide flux from a spring barley field and a cut and grazed pasture at the Teagasc Oak Park Research Centre, Co. Carlow, Ireland. In the case of the arable field, predicted fluxes of N 2 O agreed well with measured fluxes for medium to high fertilizer input (70-160 kg N ha − 1 ) but poorly described those fluxes from zero fertilizer treatments. In terms of cumulative flux values, the relative deviation of the predicted fluxes from the measured values was a maximum of 6% for the highest N fertilizer inputs but increased to 30% for the medium N and more than 100% for the zero N fertilizer treatments. There is a linear correlation of predicted against measured flux values for all fertilizer treatments (r 2 = 0.85) but the model underestimated the seasonal flux by 24%. Incorporation of literature values from a range of different studies on arable and pasture land did not significantly improve the regression. The description by DNDC for measured fluxes of N 2 O from reduced tillage plots was poor with underestimation of up to 55%. For the cut and grazed pasture the relative deviations of predicted to measured fluxes were 150 and 360% for fertilized and unfertilized plots. A sensitivity analysis suggests that the poor model fit is due to DNDC overestimating WFPS and the effect of initial soil organic carbon (SOC) on N 2 O flux. As the arable and grassland soils differed only in SOC content, reducing SOC of the grassland field to that of the arable field value significantly improved the fit of the model to measured data such that the relative deviations decreased to 9 and 5% respectively. Sensitivity analysis highlighted air temperature as the main determinant of N 2 O flux, an increase in mean daily air temperature of 1.5°C resulting in almost a 65% increase in the annual cumulative flux. This is interesting as with future global warming, N 2 O flux from the soil will have a strong positive feedback. It can be concluded that DNDC is unsuitable for predicting N 2 O from Irish grassland due to its overestimation of WFPS and effect of SOC on the flux.

Using Different Models to Estimate N2O Fluxes from Maize Cultivation in Poland

“…Gabrielle et al [46] stated that in France model-based estimates of direct N 2 O emissions from wheat-cropped field were from 39% to 81% lower than IPCC ones. In Ireland, for a spring barley field, predicted and measured fluxes of N 2 O were agreed for fertilizer doses from 70 to 160 kg N ha -1 , but did not match when the rate of N fertilizer was not applied [31]. For the cut and grazed pasture the differences of N 2 O fluxes were recorded at 150 and 360%, respectively.…”

“…Many researchers have tested the model and adopted it to country-specific management, climate, and soil conditions [30][31][32][33][34]. The DNDC model was used by the European Union (EU) to set sustainability criteria for biofuels with the legislation of the RED [4].…”

“…Therefore, in our study we have decided to use the DNDC model to assess the impact of the variability of climate conditions on N 2 O fluxes, applying different tools following Tier 1, 2, and 3 methodology. There is much research applying Tier 1 and 3 methods to a comparison of N 2 O fluxes [30][31][32]36], while the differences in N 2 O emissions between all three Tiers are presented only by Smith et al [33] and Peter et al [39]. In our study we assumed that the soil type and management practices were the same for Poland's territory in the whole country.…”

Modeling impacts of climate change and grazing effects on plant biomass and soil organic carbon in the Qinghai–Tibetan grasslands

“…The model has been used widely in more than 20 countries to obtain accurate calibration and verification results in various ecosystems (Abdalla et al, 2009;Chen et al, 2015;Li et al, 1996Li et al, , 2017Xu et al, 2003;Kariyapperuma et al, 2011;Zhao et al, 2016;Liu et al, 2006;Zhang and Niu, 2016).…”

Estimating the effect of nitrogen fertilizer on the greenhouse gas balance of soils in Wales under current and future climate

“…Fluxes of GHG were also increased with increasing air temperature. Here, microbial soil processes such as decomposition, N mineralization, nitrification and nutrient uptake are dependent on temperature (Shaver et al 2000;Shaw and Harte 2001), and consequently, so are GHG emissions (Abdalla et al 2009). …”