5-Crop-production-and-agricultural-soils/5.3-Greenhouse-gases/5.3.2-Indirect-N2O-emissions.md

@@ -14,9 +14,9 @@ Table 1  gives an overview of the methodologies applied. Since submission 2024
 
 # Leaching
 
-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.
+Nitrogen inputs into soils can cause input of nitrate to waterbodies due to runoff and leaching. These inputs to surface and ground waters cause indirect nitrous oxide emissions resulting from denitrification in these waterbodies.
 
-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 indirect N<sub>2</sub>O 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 leached 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 removal by harvest and minus the nitrogen emitted as NH<sub>3</sub> 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 leached or flows off the surface. This proportion is assumed to be constant over the entire time series.
 
 [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) estimated regional and dynamic fracleach values by combining different models. High resolution input data on the production of animals and crop, as well as on climatic and hydrological factors were used as input data, regarding the time between 2014-2016. As studies found that N surplus is a better predictor of N leaching than N input (De Notaris et al. 2018),the N surplus as well as the N losses through leaching were modeled on a high resolution by a combination of different models. This was done for the years 2014-2016, for which the calculations were averaged to prevent outliers. The N conversion processes in the soil were modeled with the DENUZ model (Kunkel & Wendland, 2006). As the high resolution spatial data for the leaching model were only available for the years 2014-2016 a regional transfer coefficient was calculated:
 
@@ -24,7 +24,7 @@ The indirect N2O emissions as a result of leaching and surface runoff are calcul
 
 Where NLeach,ref is the average annual amount of N leached in 2014–2016 modeled with RAUMIS-mGROWA-DENUZ and NSurplus,ref is the average N surplus in the same years. This coefficient was used for the whole time series to determine the regional share of the N surplus that is prone to leaching. The transfer coefficients were calculated at NUTS-1 level. The federal state Lower Saxony was divided into two regions: the north-west of the state, where livestock densities are especially high, and the south-east of the state with low livestock densities. The three City states were merged with neighboring federal states. 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).
 
-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.
+The indirect N<sub>2</sub>O emissions are calculated by multiplying the amount of N that is leached or flows off the surface with the N<sub>2</sub>O/N<sub>2</sub>O-N conversion factor 44/28, as well as the emission factor (0.011 kg N<sub>2</sub>O (kg N)<sup>-1</sup>, 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.
 
 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.