Nitrogen (N)-losses occur in agriculture when nitrogen either winds up in the atmosphere as ammonia, nitrous oxide or atmospheric nitrogen, or in water as nitrate. Ammonia contributes to the over-fertilisation and acidification of sensitive ecosystems, as well as to poor air quality. Nitrous oxide and atmospheric nitrogen are formed during farmyard-manure storage and also in the soil during denitrification and nitrification. Nitrous oxide contributes to ozone depletion in the stratosphere, and is a very potent greenhouse gas. Nitrate can leach from the soil into surface water or groundwater. Via the Rhine, it can travel into the North Sea, where it contributes to algae blooms (eutrophication) in coastal waters. Nitrate ingested with drinking water can be transformed in the human body into carcinogenic compounds.
For N-losses to the atmosphere, ammonia and nitrous oxide emissions are taken from the calculation of other AEIs. Nitrous oxide emissions are multiplied by a constant factor in order to estimate emissions of atmospheric nitrogen (N2).
Nitrate leaching is calculated at farm-plot level with the model MODIFFUS. To estimate the amount of leached nitrate, a base value for nitrate leaching is calculated with correction factors (e.g. for different seepage-water quantities, altitudes, soils). This base value depends on the combination of crops (previous year’s main crop – optional catch crop – current year’s main crop), and is taken from a database compiled using data from lysimeter trials. Where no data were available for specific base values, reasonable assumptions were derived from the available data.
Agrarbericht 2012 (PDF, 14 MB, 23.03.2021)Bundesamt für Landwirtschaft (BLW)