| ... | ... | @@ -16,19 +16,27 @@ Table 1 gives an overview of the methodologies applied. Since submission 2024 |
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Nitrogen inputs into soils are to some extent liable to runoff and leaching. The inputs into surface and ground waters give rise to indirect nitrous oxide emissions.
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The indirect N2O emissions as a result of leaching and surface runoff are calculated using a Tier 3 method since submission 2024. The methodology is based on the calculation of nitrogen surpluses, a proportion of which is washed out as nitrate or laterally displaced into receiving waters in a region-specific manner. The N surpluses are formed from the sum of the N inputs (from mineral fertilizers, manure (domestic and imported), crop residues, digestion residues, sewage sludge and composts) minus the N withdrawal in the harvest and minus the nitrogen produced when mineral and organic fertilizers are applied as NH3 -is emitted. Eysholdt et al. (2022) have modeled what proportion of the N excess at the NUTS-2 level is washed out or flows off the surface. This proportion is assumed to be constant over the entire time series. The methodology is described in detail in [Eysholdt et al. (2022)](https://juser.fz-juelich.de/record/916954/files/Journal%20of%20Plant%20Nutrition%20and%20Soil%20Science%20-%202022%20-%20Eysholdt%20-%20A%20model%E2%80%90based%20estimate%20of%20nitrate%20leaching%20in%20Germany%20for.pdf).
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The indirect N2O emissions as a result of leaching and surface runoff are calculated using a Tier 3 method since submission 2024. The methodology is based on the calculation of nitrogen surpluses, a proportion of which is washed out as nitrate or laterally displaced into receiving waters in a region-specific manner. The N surpluses are formed from the sum of the N inputs (from mineral fertilizers, manure (domestic and imported), crop residues, digestion residues, sewage sludge and composts) minus the N withdrawal in the harvest and minus the nitrogen emitted as NH3 when mineral and organic fertilizers are applied. [Eysholdt et al. (2022)](https://juser.fz-juelich.de/record/916954/files/Journal%20of%20Plant%20Nutrition%20and%20Soil%20Science%20-%202022%20-%20Eysholdt%20-%20A%20model%E2%80%90based%20estimate%20of%20nitrate%20leaching%20in%20Germany%20for.pdf) have modeled what proportion of the N excess at the NUTS-2 level is washed out or flows off the surface. This proportion is assumed to be constant over the entire time series. The methodology is described in detail in [Eysholdt et al. (2022)](https://juser.fz-juelich.de/record/916954/files/Journal%20of%20Plant%20Nutrition%20and%20Soil%20Science%20-%202022%20-%20Eysholdt%20-%20A%20model%E2%80%90based%20estimate%20of%20nitrate%20leaching%20in%20Germany%20for.pdf).
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The indirect N2O emissions are calculated by multiplying the amount of N that is leached or flows off the surface with the N2O-N conversion factor 44/28, as well as the emission factor (0.011 kg N2O-N (kg N)-1, see IPCC (2019) ). Figure XX shows that the emissions resulting from the new method are significantly lower than with the previous Tier 1 method with constant FracLEACH.
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The indirect N2O emissions are calculated by multiplying the amount of N that is leached or flows off the surface with the N2O-N conversion factor 44/28, as well as the emission factor (0.011 kg N2O-N (kg N)-1, see [IPCC (2019)](/9%20Literature#ipcc-intergovernmental-panel-on-climate-change-2019) ). Figure 1 shows that the emissions resulting from the new method are significantly lower than with the previous Tier 1 method with constant FracLEACH. The secondary axis shows the average winter wheat yield, with which the national N surplus in crop production is negatively correlated. From 2020 onwards, this correlation is overshadowed by effects of stricter fertilizer laws and high fertilizer prices.
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At the same time, emissions with the new method vary more from year to year, as the N surplus and thus the leaching depend more on the environmental conditions in the respective years. In years with poor harvests and high N inputs (e.g. 2018), there are comparatively high emissions.
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The subsequently calculated FracLEACH achieves values between 0.07 and 0.14 and is therefore within the uncertainty range specified for the new FracLEACH-(H) (0.24) in[ IPCC (2019)](/9%20Literature#ipcc-intergovernmental-panel-on-climate-change-2019) (0.01 - 0.73). The relative uncertainty range that [Eysholdt et al. (2022)](https://juser.fz-juelich.de/record/916954/files/Journal%20of%20Plant%20Nutrition%20and%20Soil%20Science%20-%202022%20-%20Eysholdt%20-%20A%20model%E2%80%90based%20estimate%20of%20nitrate%20leaching%20in%20Germany%20for.pdf) for FracLEACH (-100%, +200%) results in significantly lower absolute confidence intervals than that of the Tier 1 approach.
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**Figure 1: Comparison of annual indirect N2O emissions from leaching and surface runoff according to the IPCC 2006 Tier 1 method and the new Tier 3 method according to Eysholdt et al. (2022).**
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## Frac<sub>LEACH</sub>
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<span dir="">Frac<sub>LEACH</sub> is defined as the relative fraction of N inputs into the soil that is lost via leaching and surface runoff.</span>
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Since Submission 2024 Frac<sub>LEACH</sub> is calculated for each district and each year.
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Since Submission 2024 Frac<sub>LEACH</sub> is calculated for each district and each year.
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## Activity data
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The amount of leached N (_m_<sub>leach</sub>) that leads to indirect N<sub>2</sub>O emissions is calculated by multiplying an amount of N (_m_<sub>N, </sub>see Equation below) with the leaching factor _Frac_<sub>leach</sub>.
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The amount of leached N (_m_<sub>leach</sub>) that leads to indirect N<sub>2</sub>O emissions is calculated by multiplying an amount of N (_m_<sub>N, </sub>see Equation below) with the leaching factor _Frac_<sub>leach</sub>.
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