Spatial distribution of emissions to air - the SPREAD model

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set up for future use. Emissions of NH3 from NH3 treated straw are allocated
to conventional dairy cattle farms excluding a minor number of
suckling cattle farms that might use NH3 treated straw.
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Input data for calculation of N2O emissions from crop residue is available
in the GLR register, which include crop types on field level and
from the LPIS data due to location of the fields.
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Calculation of N2O emissions from N-fixing crops are based on data
from the GLR register on crop types on field level and from the LPIS
data where the location of the relevant fields are available.
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Distribution of N2O from histosols is based on the LPIS data in combination
with a map of organic soils in the soil map based on the Danish soil
classification. The emission is distributed evenly on the area identified
by intersection of the field area and the organic soil area.
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When the fields are fertilised part of the applied N is not assimilated by
the crops. The surplus cause leaching and run-off, which again leads to
emission of N2O. The emission calculations are based on N-content of the
applied fertiliser, manure and sludge. The spatial distribution is based
on the recommended application rate for each crop from the GLR database
in combination with LPIS data. The leaching factor is assumed to be
independent of soil type.
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The distribution key for emission of N2O from NH3 evaporation is estimated
as a sum of NH3 from point sources and area sources covering
manure and mineral fertiliser application. This approach is subject to
some degree of inaccuracy as the emission of N2O takes place at the site
for deposition of NH3 and not at the site for evaporation of NH3 as given
in the distribution key. Introduction of a transport model to make a
deposition map would improve the distribution key. This has not been
included in SPREAD, as the available deposition maps include longrange
transboundary NH3, which is not to be included in the Danish
emission inventory. Further, NH3 from agriculture is not transported
very far before deposition and therefore the inaccuracy is assumed to be
of little importance for the allocation of the emissions.
All NH3 emissions from the Danish territory are included in the emissions
distribution although studies have shown that only part of the
Danish ammonia emission is deposited on the Danish area. The Danish
share of the NH3 deposition on Danish land area is around 36 % and the
corresponding share for the Danish sea area is 14 % (Ellermann et al.
2010.