soil - Lublin

than in the night while CH 4 uptake did not vary markedly. In an additional study
Maljanen et al. (2003c) found rather good agreement between N 2 O emissions determined
with closed chamber method and those calculated according to Fick’s law
on the basis of gas concentration gradient in soil or snow.
In the summary of a PhD thesis by Nykänen (2003) is concluded that Finnish
natural peatlands, especially the fertile ones, can be significant sources of CH 4 but
they usually have no N 2 O emissions. A permanently lowered water table decreased
the emissions from minerotrophic boreal peatlands and occasionally led to CH 4
uptake while at nutrient poor peatlands the decrease in emission rate was small. In
the former peatlands drainage led to increased N 2 O emissions while there was no
change in the latter ones.
RESEARCH AT MTT AGRIFOOD RESEARCH FINLAND, JOKIOINEN
N 2 O emissions were monitored during 2000-2002 on loamy sand and on clay
soil under grass, barley and fallow (Syväsalo et al. 2004a). The fluxes were measured
with static chamber throughout the year. The annual fluxes from the clay soil
ranged from 3.7 to 7.9 kg N ha -1 and those from sandy loam 1.5 – 7.5 kg N ha -1 . On
average 60% of the fluxes occurred outside the growing season, from October to
April. Amount of applied N fertiliser did not correlate closely with variation in
N 2 O fluxes. Soil pore size distribution explained the variation somewhat. On the
clay field the highest fluxes came from the fallow plots and on the sandy field from
the barley plots, but the differences were not statistically significant.
Emissions of N 2 O were measured from field plots of grass, barley, potatoes and
fallow on a peat field in northern Finland during 2000-2002 and in southern
Finland in 1999-2002 (Regina et al. 2004). The mean annual fluxes were as follows,
kg N ha -1 a -1 :
grass barley fallow
mean SD mean SD mean SD
North 4.0 1.2 13 3.0 4.4 0.8
South 7.3 1.2 15 2.6 25 6.9
The direct effect of adding N fertiliser on N 2 O emissions was not important.
Half of the annual flux entered the atmosphere outside the growing season (October
– April). The authors conclude that the larger N 2 O fluxes in the south might be
due to the more humified status of the peat, more rapid mineralisation and weather
with more cycles of freezing and thawing in the winter.
In an incubation experiment with peat, clay and loamy sand at soil moistures
40, 60, 80 and 100% Water Filled Pore Space the highest N 2 O emission was recorded
in the wettest soils (Pihlatie et al. 2004), being up to 10 000 times higher
than in the dry soils. The emission from dry soils followed the sequence loamy
sand < clay < peat while in the wet soils the order was clay < peat < loamy sand.
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