Denmark's National Inventory Report 2005 - Submitted under the ...

N-fixing crops
To estimate the emission from N-fixing crops IPCC Tier1b is applied. The calculated emission is
based on nitrogen content, the fraction of dry matter and the content of protein for each harvest
crop type. Data for crop yield is based on Statistics Denmark. For nitrogen content in the plants the
data is taken from Danish feedstuff tables (Danish Agricultural Advisory Centre). The estimates
for the amount of fixed nitrogen in crops are estimated by Danish Institute of Agricultural Science
(Kristensen 2003, Høgh-Jensen et al. 1998, Kyllingsbæk 2000). The inventory includes emission
from clover-grass, despite the fact that this source is not mentioned in IPCC GPG. BNF from clover
in grass fields contributes with 63% of the total in 2003. In Table 6.19 is given the background data
for estimating the N-fixing. The emission from N-fixing crops decreases from 1990-2003, which is
mainly due to a reduction in the agricultural area.
Table 6.19 Emissions from N-fixing crops 2003
N2O emission
from nitrogen fixing crops
154
Dry matter
Fraction
N-fixing
Variations
1990-2003
2003 2003
N-Fraction kg N/ha kg N/ha Kg N fix
total
Pulses* 0.85 0.0337 96-179 149 4 663
Lucerne 0.21 0.0064 307-517 409 1 613
Cereals and pulses for green fodder 0.23 0.0061 16-38 22 2 465
Pulses, fodder cabbage etc. 0.23 0.0061 0-1 NO NO
Peas for canning* 0.85 0.0337 76-139 119 403
Seeds for sowing NE NE 181-186** 182 779
Grass and clover field in rotation 0.13 0.0052 41-94 89 18 774
Grass and clover outside rotation 0.13 0.0052 6-11 8 1 460
Aftermath 0.13 0.0052 6-15 9 1 785
Total N-fix 31 942
* Dry matter content for straw is 0.87 and the N-fraction is 0.010.
** Average - assumed that N-fix for red clover is 200 kg N/ha and 180 kg N/ha for white clover (Kyllingsbæk
2000)
Crop Residue
N O emissions from crop residues are calculated as the total aboveground amount of crop residues
2
returned to soil. For cereals the aboveground residues are calculated as the amount of straw plus
stubble and husks. The total amount of straw is given in the annual census and reduced with the
amount used for feeding, bedding and biofuel in power plants. Straw for feeding and bedding is
subtracted in the calculation because this amount of removed nitrogen returns to the soil via manure.
Data for nitrogen content in stubble and husks are provided by the Danish Institute of Agricultural
Sciences (Djurhuus and Hansen 2003). Background data is given in Annex 3D, Table 11.
From 1990 to 2003 there have been some changes in the cultivation of crop types, but the total
emission from crop residue is nearly unaltered (Table 6.20). The fraction of nitrogen in harvest
crop residue has decreased due to a decrease in areas with sugarbeets, which is replaced by green
maize.